[ViewVC] Diff of: cvs/IO-AIO/README

Comparing IO-AIO/README (file contents):
Revision 1.47 by root, Fri May 27 00:44:49 2011 UTC vs.
Revision 1.59 by root, Tue Feb 20 06:54:47 2018 UTC

…		…
1	NAME	1	NAME
2	IO::AIO - Asynchronous Input/Output	2	IO::AIO - Asynchronous/Advanced Input/Output
3		3
4	SYNOPSIS	4	SYNOPSIS
5	use IO::AIO;	5	use IO::AIO;
6		6
7	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {	7	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
55	not well-supported or restricted (GNU/Linux doesn't allow them on normal	55	not well-supported or restricted (GNU/Linux doesn't allow them on normal
56	files currently, for example), and they would only support aio_read and	56	files currently, for example), and they would only support aio_read and
57	aio_write, so the remaining functionality would have to be implemented	57	aio_write, so the remaining functionality would have to be implemented
58	using threads anyway.	58	using threads anyway.
59		59
		60	In addition to asynchronous I/O, this module also exports some rather
		61	arcane interfaces, such as "madvise" or linux's "splice" system call,
		62	which is why the "A" in "AIO" can also mean advanced.
		63
60	Although the module will work in the presence of other (Perl-) threads,	64	Although the module will work in the presence of other (Perl-) threads,
61	it is currently not reentrant in any way, so use appropriate locking	65	it is currently not reentrant in any way, so use appropriate locking
62	yourself, always call "poll_cb" from within the same thread, or never	66	yourself, always call "poll_cb" from within the same thread, or never
63	call "poll_cb" (or other "aio_" functions) recursively.	67	call "poll_cb" (or other "aio_" functions) recursively.
64		68
65	EXAMPLE	69	EXAMPLE
66	This is a simple example that uses the EV module and loads /etc/passwd	70	This is a simple example that uses the EV module and loads /etc/passwd
67	asynchronously:	71	asynchronously:
68		72
69	use Fcntl;
70	use EV;	73	use EV;
71	use IO::AIO;	74	use IO::AIO;
72		75
73	# register the IO::AIO callback with EV	76	# register the IO::AIO callback with EV
74	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;	77	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
…		…
91		94
92	# file contents now in $contents	95	# file contents now in $contents
93	print $contents;	96	print $contents;
94		97
95	# exit event loop and program	98	# exit event loop and program
96	EV::unloop;	99	EV::break;
97	};	100	};
98	};	101	};
99		102
100	# possibly queue up other requests, or open GUI windows,	103	# possibly queue up other requests, or open GUI windows,
101	# check for sockets etc. etc.	104	# check for sockets etc. etc.
102		105
103	# process events as long as there are some:	106	# process events as long as there are some:
104	EV::loop;	107	EV::run;
105		108
106	REQUEST ANATOMY AND LIFETIME	109	REQUEST ANATOMY AND LIFETIME
107	Every "aio_*" function creates a request. which is a C data structure	110	Every "aio_*" function creates a request. which is a C data structure
108	not directly visible to Perl.	111	not directly visible to Perl.
109		112
…		…
146	the actual aio request is severed and calling its methods will	149	the actual aio request is severed and calling its methods will
147	either do nothing or result in a runtime error).	150	either do nothing or result in a runtime error).
148		151
149	FUNCTIONS	152	FUNCTIONS
150	QUICK OVERVIEW	153	QUICK OVERVIEW
151	This section simply lists the prototypes of the most important functions	154	This section simply lists the prototypes most of the functions for quick
152	for quick reference. See the following sections for function-by-function	155	reference. See the following sections for function-by-function
153	documentation.	156	documentation.
154		157
		158	aio_wd $pathname, $callback->($wd)
155	aio_open $pathname, $flags, $mode, $callback->($fh)	159	aio_open $pathname, $flags, $mode, $callback->($fh)
156	aio_close $fh, $callback->($status)	160	aio_close $fh, $callback->($status)
		161	aio_seek $fh,$offset,$whence, $callback->($offs)
157	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	162	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
158	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	163	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	164	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
160	aio_readahead $fh,$offset,$length, $callback->($retval)	165	aio_readahead $fh,$offset,$length, $callback->($retval)
161	aio_stat $fh_or_path, $callback->($status)	166	aio_stat $fh_or_path, $callback->($status)
162	aio_lstat $fh, $callback->($status)	167	aio_lstat $fh, $callback->($status)
163	aio_statvfs $fh_or_path, $callback->($statvfs)	168	aio_statvfs $fh_or_path, $callback->($statvfs)
164	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	169	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
165	aio_chown $fh_or_path, $uid, $gid, $callback->($status)	170	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		171	aio_chmod $fh_or_path, $mode, $callback->($status)
166	aio_truncate $fh_or_path, $offset, $callback->($status)	172	aio_truncate $fh_or_path, $offset, $callback->($status)
167	aio_chmod $fh_or_path, $mode, $callback->($status)	173	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		174	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
168	aio_unlink $pathname, $callback->($status)	175	aio_unlink $pathname, $callback->($status)
169	aio_mknod $path, $mode, $dev, $callback->($status)	176	aio_mknod $pathname, $mode, $dev, $callback->($status)
170	aio_link $srcpath, $dstpath, $callback->($status)	177	aio_link $srcpath, $dstpath, $callback->($status)
171	aio_symlink $srcpath, $dstpath, $callback->($status)	178	aio_symlink $srcpath, $dstpath, $callback->($status)
172	aio_readlink $path, $callback->($link)	179	aio_readlink $pathname, $callback->($link)
		180	aio_realpath $pathname, $callback->($path)
173	aio_rename $srcpath, $dstpath, $callback->($status)	181	aio_rename $srcpath, $dstpath, $callback->($status)
		182	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
174	aio_mkdir $pathname, $mode, $callback->($status)	183	aio_mkdir $pathname, $mode, $callback->($status)
175	aio_rmdir $pathname, $callback->($status)	184	aio_rmdir $pathname, $callback->($status)
176	aio_readdir $pathname, $callback->($entries)	185	aio_readdir $pathname, $callback->($entries)
177	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	186	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
178	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	187	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
179	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN	188	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		189	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
180	aio_load $path, $data, $callback->($status)	190	aio_load $pathname, $data, $callback->($status)
181	aio_copy $srcpath, $dstpath, $callback->($status)	191	aio_copy $srcpath, $dstpath, $callback->($status)
182	aio_move $srcpath, $dstpath, $callback->($status)	192	aio_move $srcpath, $dstpath, $callback->($status)
183	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
184	aio_rmtree $path, $callback->($status)	193	aio_rmtree $pathname, $callback->($status)
		194	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		195	aio_ioctl $fh, $request, $buf, $callback->($status)
185	aio_sync $callback->($status)	196	aio_sync $callback->($status)
		197	aio_syncfs $fh, $callback->($status)
186	aio_fsync $fh, $callback->($status)	198	aio_fsync $fh, $callback->($status)
187	aio_fdatasync $fh, $callback->($status)	199	aio_fdatasync $fh, $callback->($status)
188	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	200	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
189	aio_pathsync $path, $callback->($status)	201	aio_pathsync $pathname, $callback->($status)
190	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	202	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
191	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	203	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
192	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	204	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
193	aio_mlockall $flags, $callback->($status)	205	aio_mlockall $flags, $callback->($status)
194	aio_group $callback->(...)	206	aio_group $callback->(...)
195	aio_nop $callback->()	207	aio_nop $callback->()
…		…
209	IO::AIO::idle_timeout $seconds	221	IO::AIO::idle_timeout $seconds
210	IO::AIO::max_outstanding $maxreqs	222	IO::AIO::max_outstanding $maxreqs
211	IO::AIO::nreqs	223	IO::AIO::nreqs
212	IO::AIO::nready	224	IO::AIO::nready
213	IO::AIO::npending	225	IO::AIO::npending
		226	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		227	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
214		228
215	IO::AIO::sendfile $ofh, $ifh, $offset, $count	229	IO::AIO::sendfile $ofh, $ifh, $offset, $count
216	IO::AIO::fadvise $fh, $offset, $len, $advice	230	IO::AIO::fadvise $fh, $offset, $len, $advice
		231	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		232	IO::AIO::munmap $scalar
217	IO::AIO::madvise $scalar, $offset, $length, $advice	233	IO::AIO::madvise $scalar, $offset, $length, $advice
218	IO::AIO::mprotect $scalar, $offset, $length, $protect	234	IO::AIO::mprotect $scalar, $offset, $length, $protect
219	IO::AIO::munlock $scalar, $offset = 0, $length = undef	235	IO::AIO::munlock $scalar, $offset = 0, $length = undef
220	IO::AIO::munlockall	236	IO::AIO::munlockall
221		237
222	AIO REQUEST FUNCTIONS	238	API NOTES
223	All the "aio_*" calls are more or less thin wrappers around the syscall	239	All the "aio_*" calls are more or less thin wrappers around the syscall
224	with the same name (sans "aio_"). The arguments are similar or	240	with the same name (sans "aio_"). The arguments are similar or
225	identical, and they all accept an additional (and optional) $callback	241	identical, and they all accept an additional (and optional) $callback
226	argument which must be a code reference. This code reference will get	242	argument which must be a code reference. This code reference will be
227	called with the syscall return code (e.g. most syscalls return -1 on
228	error, unlike perl, which usually delivers "false") as its sole argument
229	after the given syscall has been executed asynchronously.	243	called after the syscall has been executed in an asynchronous fashion.
		244	The results of the request will be passed as arguments to the callback
		245	(and, if an error occured, in $!) - for most requests the syscall return
		246	code (e.g. most syscalls return -1 on error, unlike perl, which usually
		247	delivers "false").
		248
		249	Some requests (such as "aio_readdir") pass the actual results and
		250	communicate failures by passing "undef".
230		251
231	All functions expecting a filehandle keep a copy of the filehandle	252	All functions expecting a filehandle keep a copy of the filehandle
232	internally until the request has finished.	253	internally until the request has finished.
233		254
234	All functions return request objects of type IO::AIO::REQ that allow	255	All functions return request objects of type IO::AIO::REQ that allow
235	further manipulation of those requests while they are in-flight.	256	further manipulation of those requests while they are in-flight.
236		257
237	The pathnames you pass to these routines must be absolute and encoded	258	The pathnames you pass to these routines should be absolute. The
238	as octets. The reason for the former is that at the time the request is	259	reason for this is that at the time the request is being executed, the
239	being executed, the current working directory could have changed.	260	current working directory could have changed. Alternatively, you can
240	Alternatively, you can make sure that you never change the current	261	make sure that you never change the current working directory anywhere
241	working directory anywhere in the program and then use relative paths.	262	in the program and then use relative paths. You can also take advantage
		263	of IO::AIOs working directory abstraction, that lets you specify paths
		264	relative to some previously-opened "working directory object" - see the
		265	description of the "IO::AIO::WD" class later in this document.
242		266
243	To encode pathnames as octets, either make sure you either: a) always	267	To encode pathnames as octets, either make sure you either: a) always
244	pass in filenames you got from outside (command line, readdir etc.)	268	pass in filenames you got from outside (command line, readdir etc.)
245	without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module	269	without tinkering, b) are in your native filesystem encoding, c) use the
246	and encode your pathnames to the locale (or other) encoding in effect in	270	Encode module and encode your pathnames to the locale (or other)
247	the user environment, d) use Glib::filename_from_unicode on unicode	271	encoding in effect in the user environment, d) use
248	filenames or e) use something else to ensure your scalar has the correct	272	Glib::filename_from_unicode on unicode filenames or e) use something
249	contents.	273	else to ensure your scalar has the correct contents.
250		274
251	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	275	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
252	handles correctly whether it is set or not.	276	handles correctly whether it is set or not.
253		277
		278	AIO REQUEST FUNCTIONS
254	$prev_pri = aioreq_pri [$pri]	279	$prev_pri = aioreq_pri [$pri]
255	Returns the priority value that would be used for the next request	280	Returns the priority value that would be used for the next request
256	and, if $pri is given, sets the priority for the next aio request.	281	and, if $pri is given, sets the priority for the next aio request.
257		282
258	The default priority is 0, the minimum and maximum priorities are -4	283	The default priority is 0, the minimum and maximum priorities are -4
…		…
280	Similar to "aioreq_pri", but subtracts the given value from the	305	Similar to "aioreq_pri", but subtracts the given value from the
281	current priority, so the effect is cumulative.	306	current priority, so the effect is cumulative.
282		307
283	aio_open $pathname, $flags, $mode, $callback->($fh)	308	aio_open $pathname, $flags, $mode, $callback->($fh)
284	Asynchronously open or create a file and call the callback with a	309	Asynchronously open or create a file and call the callback with a
285	newly created filehandle for the file.	310	newly created filehandle for the file (or "undef" in case of an
		311	error).
286		312
287	The pathname passed to "aio_open" must be absolute. See API NOTES,	313	The pathname passed to "aio_open" must be absolute. See API NOTES,
288	above, for an explanation.	314	above, for an explanation.
289		315
290	The $flags argument is a bitmask. See the "Fcntl" module for a list.	316	The $flags argument is a bitmask. See the "Fcntl" module for a list.
…		…
313	"O_APPEND"), the following POSIX and non-POSIX constants are	339	"O_APPEND"), the following POSIX and non-POSIX constants are
314	available (missing ones on your system are, as usual, 0):	340	available (missing ones on your system are, as usual, 0):
315		341
316	"O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",	342	"O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
317	"O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",	343	"O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
318	"O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".	344	"O_DSYNC", "O_RSYNC", "O_SYNC", "O_PATH", "O_TMPFILE", and
		345	"O_TTY_INIT".
319		346
320	aio_close $fh, $callback->($status)	347	aio_close $fh, $callback->($status)
321	Asynchronously close a file and call the callback with the result	348	Asynchronously close a file and call the callback with the result
322	code.	349	code.
323		350
…		…
329	will use dup2 to overwrite the file descriptor with the write-end of	356	will use dup2 to overwrite the file descriptor with the write-end of
330	a pipe (the pipe fd will be created on demand and will be cached).	357	a pipe (the pipe fd will be created on demand and will be cached).
331		358
332	Or in other words: the file descriptor will be closed, but it will	359	Or in other words: the file descriptor will be closed, but it will
333	not be free for reuse until the perl filehandle is closed.	360	not be free for reuse until the perl filehandle is closed.
		361
		362	aio_seek $fh, $offset, $whence, $callback->($offs)
		363	Seeks the filehandle to the new $offset, similarly to perl's
		364	"sysseek". The $whence can use the traditional values (0 for
		365	"IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
		366	"IO::AIO::SEEK_END").
		367
		368	The resulting absolute offset will be passed to the callback, or -1
		369	in case of an error.
		370
		371	In theory, the $whence constants could be different than the
		372	corresponding values from Fcntl, but perl guarantees they are the
		373	same, so don't panic.
		374
		375	As a GNU/Linux (and maybe Solaris) extension, also the constants
		376	"IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
		377	could be found. No guarantees about suitability for use in
		378	"aio_seek" or Perl's "sysseek" can be made though, although I would
		379	naively assume they "just work".
334		380
335	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	381	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
336	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	382	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
337	Reads or writes $length bytes from or to the specified $fh and	383	Reads or writes $length bytes from or to the specified $fh and
338	$offset into the scalar given by $data and offset $dataoffset and	384	$offset into the scalar given by $data and offset $dataoffset and
339	calls the callback without the actual number of bytes read (or -1 on	385	calls the callback with the actual number of bytes transferred (or
340	error, just like the syscall).	386	-1 on error, just like the syscall).
341		387
342	"aio_read" will, like "sysread", shrink or grow the $data scalar to	388	"aio_read" will, like "sysread", shrink or grow the $data scalar to
343	offset plus the actual number of bytes read.	389	offset plus the actual number of bytes read.
344		390
345	If $offset is undefined, then the current file descriptor offset	391	If $offset is undefined, then the current file descriptor offset
…		…
367	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	413	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
368	Tries to copy $length bytes from $in_fh to $out_fh. It starts	414	Tries to copy $length bytes from $in_fh to $out_fh. It starts
369	reading at byte offset $in_offset, and starts writing at the current	415	reading at byte offset $in_offset, and starts writing at the current
370	file offset of $out_fh. Because of that, it is not safe to issue	416	file offset of $out_fh. Because of that, it is not safe to issue
371	more than one "aio_sendfile" per $out_fh, as they will interfere	417	more than one "aio_sendfile" per $out_fh, as they will interfere
372	with each other.	418	with each other. The same $in_fh works fine though, as this function
		419	does not move or use the file offset of $in_fh.
373		420
374	Please note that "aio_sendfile" can read more bytes from $in_fh than	421	Please note that "aio_sendfile" can read more bytes from $in_fh than
375	are written, and there is no way to find out how many bytes have	422	are written, and there is no way to find out how many more bytes
376	been read from "aio_sendfile" alone, as "aio_sendfile" only provides	423	have been read from "aio_sendfile" alone, as "aio_sendfile" only
377	the number of bytes written to $out_fh. Only if the result value	424	provides the number of bytes written to $out_fh. Only if the result
378	equals $length one can assume that $length bytes have been read.	425	value equals $length one can assume that $length bytes have been
		426	read.
379		427
380	Unlike with other "aio_" functions, it makes a lot of sense to use	428	Unlike with other "aio_" functions, it makes a lot of sense to use
381	"aio_sendfile" on non-blocking sockets, as long as one end	429	"aio_sendfile" on non-blocking sockets, as long as one end
382	(typically the $in_fh) is a file - the file I/O will then be	430	(typically the $in_fh) is a file - the file I/O will then be
383	asynchronous, while the socket I/O will be non-blocking. Note,	431	asynchronous, while the socket I/O will be non-blocking. Note,
384	however, that you can run into a trap where "aio_sendfile" reads	432	however, that you can run into a trap where "aio_sendfile" reads
385	some data with readahead, then fails to write all data, and when the	433	some data with readahead, then fails to write all data, and when the
386	socket is ready the next time, the data in the cache is already	434	socket is ready the next time, the data in the cache is already
387	lost, forcing "aio_sendfile" to again hit the disk. Explicit	435	lost, forcing "aio_sendfile" to again hit the disk. Explicit
388	"aio_read" + "aio_write" let's you control resource usage much	436	"aio_read" + "aio_write" let's you better control resource usage.
389	better.
390		437
391	This call tries to make use of a native "sendfile" syscall to	438	This call tries to make use of a native "sendfile"-like syscall to
392	provide zero-copy operation. For this to work, $out_fh should refer	439	provide zero-copy operation. For this to work, $out_fh should refer
393	to a socket, and $in_fh should refer to an mmap'able file.	440	to a socket, and $in_fh should refer to an mmap'able file.
394		441
395	If a native sendfile cannot be found or it fails with "ENOSYS",	442	If a native sendfile cannot be found or it fails with "ENOSYS",
396	"ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",	443	"EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
397	it will be emulated, so you can call "aio_sendfile" on any type of	444	"ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
398	filehandle regardless of the limitations of the operating system.	445	any type of filehandle regardless of the limitations of the
		446	operating system.
		447
		448	As native sendfile syscalls (as practically any non-POSIX interface
		449	hacked together in a hurry to improve benchmark numbers) tend to be
		450	rather buggy on many systems, this implementation tries to work
		451	around some known bugs in Linux and FreeBSD kernels (probably
		452	others, too), but that might fail, so you really really should check
		453	the return value of "aio_sendfile" - fewer bytes than expected might
		454	have been transferred.
399		455
400	aio_readahead $fh,$offset,$length, $callback->($retval)	456	aio_readahead $fh,$offset,$length, $callback->($retval)
401	"aio_readahead" populates the page cache with data from a file so	457	"aio_readahead" populates the page cache with data from a file so
402	that subsequent reads from that file will not block on disk I/O. The	458	that subsequent reads from that file will not block on disk I/O. The
403	$offset argument specifies the starting point from which data is to	459	$offset argument specifies the starting point from which data is to
…		…
406	to a page boundary and bytes are read up to the next page boundary	462	to a page boundary and bytes are read up to the next page boundary
407	greater than or equal to (off-set+length). "aio_readahead" does not	463	greater than or equal to (off-set+length). "aio_readahead" does not
408	read beyond the end of the file. The current file offset of the file	464	read beyond the end of the file. The current file offset of the file
409	is left unchanged.	465	is left unchanged.
410		466
411	If that syscall doesn't exist (likely if your OS isn't Linux) it	467	If that syscall doesn't exist (likely if your kernel isn't Linux) it
412	will be emulated by simply reading the data, which would have a	468	will be emulated by simply reading the data, which would have a
413	similar effect.	469	similar effect.
414		470
415	aio_stat $fh_or_path, $callback->($status)	471	aio_stat $fh_or_path, $callback->($status)
416	aio_lstat $fh, $callback->($status)	472	aio_lstat $fh, $callback->($status)
…		…
514	aio_chown "path", 0, undef;	570	aio_chown "path", 0, undef;
515		571
516	aio_truncate $fh_or_path, $offset, $callback->($status)	572	aio_truncate $fh_or_path, $offset, $callback->($status)
517	Works like truncate(2) or ftruncate(2).	573	Works like truncate(2) or ftruncate(2).
518		574
		575	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		576	Allocates or frees disk space according to the $mode argument. See
		577	the linux "fallocate" documentation for details.
		578
		579	$mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
		580	space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE \|
		581	IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
		582
		583	IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
		584	(without leaving a hole), "FALLOC_FL_ZERO_RANGE", to zero a range,
		585	"FALLOC_FL_INSERT_RANGE" to insert a range and
		586	"FALLOC_FL_UNSHARE_RANGE" to unshare shared blocks (see your
		587	fallocate(2) manpage).
		588
		589	The file system block size used by "fallocate" is presumably the
		590	"f_bsize" returned by "statvfs", but different filesystems and
		591	filetypes can dictate other limitations.
		592
		593	If "fallocate" isn't available or cannot be emulated (currently no
		594	emulation will be attempted), passes -1 and sets $! to "ENOSYS".
		595
519	aio_chmod $fh_or_path, $mode, $callback->($status)	596	aio_chmod $fh_or_path, $mode, $callback->($status)
520	Works like perl's "chmod" function.	597	Works like perl's "chmod" function.
521		598
522	aio_unlink $pathname, $callback->($status)	599	aio_unlink $pathname, $callback->($status)
523	Asynchronously unlink (delete) a file and call the callback with the	600	Asynchronously unlink (delete) a file and call the callback with the
524	result code.	601	result code.
525		602
526	aio_mknod $path, $mode, $dev, $callback->($status)	603	aio_mknod $pathname, $mode, $dev, $callback->($status)
527	[EXPERIMENTAL]	604	[EXPERIMENTAL]
528		605
529	Asynchronously create a device node (or fifo). See mknod(2).	606	Asynchronously create a device node (or fifo). See mknod(2).
530		607
531	The only (POSIX-) portable way of calling this function is:	608	The only (POSIX-) portable way of calling this function is:
532		609
533	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...	610	aio_mknod $pathname, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
534		611
535	See "aio_stat" for info about some potentially helpful extra	612	See "aio_stat" for info about some potentially helpful extra
536	constants and functions.	613	constants and functions.
537		614
538	aio_link $srcpath, $dstpath, $callback->($status)	615	aio_link $srcpath, $dstpath, $callback->($status)
…		…
542	aio_symlink $srcpath, $dstpath, $callback->($status)	619	aio_symlink $srcpath, $dstpath, $callback->($status)
543	Asynchronously create a new symbolic link to the existing object at	620	Asynchronously create a new symbolic link to the existing object at
544	$srcpath at the path $dstpath and call the callback with the result	621	$srcpath at the path $dstpath and call the callback with the result
545	code.	622	code.
546		623
547	aio_readlink $path, $callback->($link)	624	aio_readlink $pathname, $callback->($link)
548	Asynchronously read the symlink specified by $path and pass it to	625	Asynchronously read the symlink specified by $path and pass it to
549	the callback. If an error occurs, nothing or undef gets passed to	626	the callback. If an error occurs, nothing or undef gets passed to
550	the callback.	627	the callback.
551		628
		629	aio_realpath $pathname, $callback->($path)
		630	Asynchronously make the path absolute and resolve any symlinks in
		631	$path. The resulting path only consists of directories (same as
		632	Cwd::realpath).
		633
		634	This request can be used to get the absolute path of the current
		635	working directory by passing it a path of . (a single dot).
		636
552	aio_rename $srcpath, $dstpath, $callback->($status)	637	aio_rename $srcpath, $dstpath, $callback->($status)
553	Asynchronously rename the object at $srcpath to $dstpath, just as	638	Asynchronously rename the object at $srcpath to $dstpath, just as
554	rename(2) and call the callback with the result code.	639	rename(2) and call the callback with the result code.
		640
		641	On systems that support the AIO::WD working directory abstraction
		642	natively, the case "[$wd, "."]" as $srcpath is specialcased -
		643	instead of failing, "rename" is called on the absolute path of $wd.
		644
		645	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		646	Basically a version of "aio_rename" with an additional $flags
		647	argument. Calling this with "$flags=0" is the same as calling
		648	"aio_rename".
		649
		650	Non-zero flags are currently only supported on GNU/Linux systems
		651	that support renameat2. Other systems fail with "ENOSYS" in this
		652	case.
		653
		654	The following constants are available (missing ones are, as usual
		655	0), see renameat2(2) for details:
		656
		657	"IO::AIO::RENAME_NOREPLACE", "IO::AIO::RENAME_EXCHANGE" and
		658	"IO::AIO::RENAME_WHITEOUT".
555		659
556	aio_mkdir $pathname, $mode, $callback->($status)	660	aio_mkdir $pathname, $mode, $callback->($status)
557	Asynchronously mkdir (create) a directory and call the callback with	661	Asynchronously mkdir (create) a directory and call the callback with
558	the result code. $mode will be modified by the umask at the time the	662	the result code. $mode will be modified by the umask at the time the
559	request is executed, so do not change your umask.	663	request is executed, so do not change your umask.
560		664
561	aio_rmdir $pathname, $callback->($status)	665	aio_rmdir $pathname, $callback->($status)
562	Asynchronously rmdir (delete) a directory and call the callback with	666	Asynchronously rmdir (delete) a directory and call the callback with
563	the result code.	667	the result code.
564		668
		669	On systems that support the AIO::WD working directory abstraction
		670	natively, the case "[$wd, "."]" is specialcased - instead of
		671	failing, "rmdir" is called on the absolute path of $wd.
		672
565	aio_readdir $pathname, $callback->($entries)	673	aio_readdir $pathname, $callback->($entries)
566	Unlike the POSIX call of the same name, "aio_readdir" reads an	674	Unlike the POSIX call of the same name, "aio_readdir" reads an
567	entire directory (i.e. opendir + readdir + closedir). The entries	675	entire directory (i.e. opendir + readdir + closedir). The entries
568	will not be sorted, and will NOT include the "." and ".." entries.	676	will not be sorted, and will NOT include the "." and ".." entries.
569		677
570	The callback is passed a single argument which is either "undef" or	678	The callback is passed a single argument which is either "undef" or
571	an array-ref with the filenames.	679	an array-ref with the filenames.
572		680
573	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	681	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
574	Quite similar to "aio_readdir", but the $flags argument allows to	682	Quite similar to "aio_readdir", but the $flags argument allows one
575	tune behaviour and output format. In case of an error, $entries will	683	to tune behaviour and output format. In case of an error, $entries
576	be "undef".	684	will be "undef".
577		685
578	The flags are a combination of the following constants, ORed	686	The flags are a combination of the following constants, ORed
579	together (the flags will also be passed to the callback, possibly	687	together (the flags will also be passed to the callback, possibly
580	modified):	688	modified):
581		689
…		…
626	optimal stat order.	734	optimal stat order.
627		735
628	IO::AIO::READDIR_FOUND_UNKNOWN	736	IO::AIO::READDIR_FOUND_UNKNOWN
629	This flag should not be set when calling "aio_readdirx".	737	This flag should not be set when calling "aio_readdirx".
630	Instead, it is being set by "aio_readdirx", when any of the	738	Instead, it is being set by "aio_readdirx", when any of the
631	$type's found were "IO::AIO::DT_UNKNOWN". The absense of this	739	$type's found were "IO::AIO::DT_UNKNOWN". The absence of this
632	flag therefore indicates that all $type's are known, which can	740	flag therefore indicates that all $type's are known, which can
633	be used to speed up some algorithms.	741	be used to speed up some algorithms.
634		742
		743	aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		744	Opens, reads and closes the given file. The data is put into $data,
		745	which is resized as required.
		746
		747	If $offset is negative, then it is counted from the end of the file.
		748
		749	If $length is zero, then the remaining length of the file is used.
		750	Also, in this case, the same limitations to modifying $data apply as
		751	when IO::AIO::mmap is used, i.e. it must only be modified in-place
		752	with "substr". If the size of the file is known, specifying a
		753	non-zero $length results in a performance advantage.
		754
		755	This request is similar to the older "aio_load" request, but since
		756	it is a single request, it might be more efficient to use.
		757
		758	Example: load /etc/passwd into $passwd.
		759
		760	my $passwd;
		761	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		762	$_[0] >= 0
		763	or die "/etc/passwd: $!\n";
		764
		765	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		766	print $passwd;
		767	};
		768	IO::AIO::flush;
		769
635	aio_load $path, $data, $callback->($status)	770	aio_load $pathname, $data, $callback->($status)
636	This is a composite request that tries to fully load the given file	771	This is a composite request that tries to fully load the given file
637	into memory. Status is the same as with aio_read.	772	into memory. Status is the same as with aio_read.
		773
		774	Using "aio_slurp" might be more efficient, as it is a single
		775	request.
638		776
639	aio_copy $srcpath, $dstpath, $callback->($status)	777	aio_copy $srcpath, $dstpath, $callback->($status)
640	Try to copy the file (directories not supported as either source	778	Try to copy the file (directories not supported as either source
641	or destination) from $srcpath to $dstpath and call the callback with	779	or destination) from $srcpath to $dstpath and call the callback with
642	a status of 0 (ok) or -1 (error, see $!).	780	a status of 0 (ok) or -1 (error, see $!).
643		781
		782	Existing destination files will be truncated.
		783
644	This is a composite request that creates the destination file with	784	This is a composite request that creates the destination file with
645	mode 0200 and copies the contents of the source file into it using	785	mode 0200 and copies the contents of the source file into it using
646	"aio_sendfile", followed by restoring atime, mtime, access mode and	786	"aio_sendfile", followed by restoring atime, mtime, access mode and
647	uid/gid, in that order.	787	uid/gid, in that order.
648		788
…		…
657		797
658	This is a composite request that tries to rename(2) the file first;	798	This is a composite request that tries to rename(2) the file first;
659	if rename fails with "EXDEV", it copies the file with "aio_copy"	799	if rename fails with "EXDEV", it copies the file with "aio_copy"
660	and, if that is successful, unlinks the $srcpath.	800	and, if that is successful, unlinks the $srcpath.
661		801
662	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	802	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
663	Scans a directory (similar to "aio_readdir") but additionally tries	803	Scans a directory (similar to "aio_readdir") but additionally tries
664	to efficiently separate the entries of directory $path into two sets	804	to efficiently separate the entries of directory $path into two sets
665	of names, directories you can recurse into (directories), and ones	805	of names, directories you can recurse into (directories), and ones
666	you cannot recurse into (everything else, including symlinks to	806	you cannot recurse into (everything else, including symlinks to
667	directories).	807	directories).
668		808
669	"aio_scandir" is a composite request that creates of many sub	809	"aio_scandir" is a composite request that generates many sub
670	requests_ $maxreq specifies the maximum number of outstanding aio	810	requests. $maxreq specifies the maximum number of outstanding aio
671	requests that this function generates. If it is "<= 0", then a	811	requests that this function generates. If it is "<= 0", then a
672	suitable default will be chosen (currently 4).	812	suitable default will be chosen (currently 4).
673		813
674	On error, the callback is called without arguments, otherwise it	814	On error, the callback is called without arguments, otherwise it
675	receives two array-refs with path-relative entry names.	815	receives two array-refs with path-relative entry names.
…		…
700	Then entries will be sorted into likely directories a non-initial	840	Then entries will be sorted into likely directories a non-initial
701	dot currently) and likely non-directories (see "aio_readdirx"). Then	841	dot currently) and likely non-directories (see "aio_readdirx"). Then
702	every entry plus an appended "/." will be "stat"'ed, likely	842	every entry plus an appended "/." will be "stat"'ed, likely
703	directories first, in order of their inode numbers. If that	843	directories first, in order of their inode numbers. If that
704	succeeds, it assumes that the entry is a directory or a symlink to	844	succeeds, it assumes that the entry is a directory or a symlink to
705	directory (which will be checked seperately). This is often faster	845	directory (which will be checked separately). This is often faster
706	than stat'ing the entry itself because filesystems might detect the	846	than stat'ing the entry itself because filesystems might detect the
707	type of the entry without reading the inode data (e.g. ext2fs	847	type of the entry without reading the inode data (e.g. ext2fs
708	filetype feature), even on systems that cannot return the filetype	848	filetype feature), even on systems that cannot return the filetype
709	information on readdir.	849	information on readdir.
710		850
…		…
716		856
717	It will also likely work on non-POSIX filesystems with reduced	857	It will also likely work on non-POSIX filesystems with reduced
718	efficiency as those tend to return 0 or 1 as link counts, which	858	efficiency as those tend to return 0 or 1 as link counts, which
719	disables the directory counting heuristic.	859	disables the directory counting heuristic.
720		860
721	aio_rmtree $path, $callback->($status)	861	aio_rmtree $pathname, $callback->($status)
722	Delete a directory tree starting (and including) $path, return the	862	Delete a directory tree starting (and including) $path, return the
723	status of the final "rmdir" only. This is a composite request that	863	status of the final "rmdir" only. This is a composite request that
724	uses "aio_scandir" to recurse into and rmdir directories, and unlink	864	uses "aio_scandir" to recurse into and rmdir directories, and unlink
725	everything else.	865	everything else.
726		866
		867	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		868	aio_ioctl $fh, $request, $buf, $callback->($status)
		869	These work just like the "fcntl" and "ioctl" built-in functions,
		870	except they execute asynchronously and pass the return value to the
		871	callback.
		872
		873	Both calls can be used for a lot of things, some of which make more
		874	sense to run asynchronously in their own thread, while some others
		875	make less sense. For example, calls that block waiting for external
		876	events, such as locking, will also lock down an I/O thread while it
		877	is waiting, which can deadlock the whole I/O system. At the same
		878	time, there might be no alternative to using a thread to wait.
		879
		880	So in general, you should only use these calls for things that do
		881	(filesystem) I/O, not for things that wait for other events
		882	(network, other processes), although if you are careful and know
		883	what you are doing, you still can.
		884
		885	The following constants are available (missing ones are, as usual
		886	0):
		887
		888	"F_DUPFD_CLOEXEC",
		889
		890	"F_OFD_GETLK", "F_OFD_SETLK", "F_OFD_GETLKW",
		891
		892	"FIFREEZE", "FITHAW", "FITRIM", "FICLONE", "FICLONERANGE",
		893	"FIDEDUPERANGE".
		894
		895	"FS_IOC_GETFLAGS", "FS_IOC_SETFLAGS", "FS_IOC_GETVERSION",
		896	"FS_IOC_SETVERSION", "FS_IOC_FIEMAP".
		897
		898	"FS_IOC_FSGETXATTR", "FS_IOC_FSSETXATTR",
		899	"FS_IOC_SET_ENCRYPTION_POLICY", "FS_IOC_GET_ENCRYPTION_PWSALT",
		900	"FS_IOC_GET_ENCRYPTION_POLICY", "FS_KEY_DESCRIPTOR_SIZE".
		901
		902	"FS_SECRM_FL", "FS_UNRM_FL", "FS_COMPR_FL", "FS_SYNC_FL",
		903	"FS_IMMUTABLE_FL", "FS_APPEND_FL", "FS_NODUMP_FL", "FS_NOATIME_FL",
		904	"FS_DIRTY_FL", "FS_COMPRBLK_FL", "FS_NOCOMP_FL", "FS_ENCRYPT_FL",
		905	"FS_BTREE_FL", "FS_INDEX_FL", "FS_JOURNAL_DATA_FL", "FS_NOTAIL_FL",
		906	"FS_DIRSYNC_FL", "FS_TOPDIR_FL", "FS_FL_USER_MODIFIABLE".
		907
		908	"FS_XFLAG_REALTIME", "FS_XFLAG_PREALLOC", "FS_XFLAG_IMMUTABLE",
		909	"FS_XFLAG_APPEND", "FS_XFLAG_SYNC", "FS_XFLAG_NOATIME",
		910	"FS_XFLAG_NODUMP", "FS_XFLAG_RTINHERIT", "FS_XFLAG_PROJINHERIT",
		911	"FS_XFLAG_NOSYMLINKS", "FS_XFLAG_EXTSIZE", "FS_XFLAG_EXTSZINHERIT",
		912	"FS_XFLAG_NODEFRAG", "FS_XFLAG_FILESTREAM", "FS_XFLAG_DAX",
		913	"FS_XFLAG_HASATTR",
		914
727	aio_sync $callback->($status)	915	aio_sync $callback->($status)
728	Asynchronously call sync and call the callback when finished.	916	Asynchronously call sync and call the callback when finished.
729		917
730	aio_fsync $fh, $callback->($status)	918	aio_fsync $fh, $callback->($status)
731	Asynchronously call fsync on the given filehandle and call the	919	Asynchronously call fsync on the given filehandle and call the
…		…
735	Asynchronously call fdatasync on the given filehandle and call the	923	Asynchronously call fdatasync on the given filehandle and call the
736	callback with the fdatasync result code.	924	callback with the fdatasync result code.
737		925
738	If this call isn't available because your OS lacks it or it couldn't	926	If this call isn't available because your OS lacks it or it couldn't
739	be detected, it will be emulated by calling "fsync" instead.	927	be detected, it will be emulated by calling "fsync" instead.
		928
		929	aio_syncfs $fh, $callback->($status)
		930	Asynchronously call the syncfs syscall to sync the filesystem
		931	associated to the given filehandle and call the callback with the
		932	syncfs result code. If syncfs is not available, calls sync(), but
		933	returns -1 and sets errno to "ENOSYS" nevertheless.
740		934
741	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	935	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
742	Sync the data portion of the file specified by $offset and $length	936	Sync the data portion of the file specified by $offset and $length
743	to disk (but NOT the metadata), by calling the Linux-specific	937	to disk (but NOT the metadata), by calling the Linux-specific
744	sync_file_range call. If sync_file_range is not available or it	938	sync_file_range call. If sync_file_range is not available or it
…		…
748	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",	942	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
749	"IO::AIO::SYNC_FILE_RANGE_WRITE" and	943	"IO::AIO::SYNC_FILE_RANGE_WRITE" and
750	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range	944	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
751	manpage for details.	945	manpage for details.
752		946
753	aio_pathsync $path, $callback->($status)	947	aio_pathsync $pathname, $callback->($status)
754	This request tries to open, fsync and close the given path. This is	948	This request tries to open, fsync and close the given path. This is
755	a composite request intended to sync directories after directory	949	a composite request intended to sync directories after directory
756	operations (E.g. rename). This might not work on all operating	950	operations (E.g. rename). This might not work on all operating
757	systems or have any specific effect, but usually it makes sure that	951	systems or have any specific effect, but usually it makes sure that
758	directory changes get written to disc. It works for anything that	952	directory changes get written to disc. It works for anything that
…		…
761	Future versions of this function might fall back to other methods	955	Future versions of this function might fall back to other methods
762	when "fsync" on the directory fails (such as calling "sync").	956	when "fsync" on the directory fails (such as calling "sync").
763		957
764	Passes 0 when everything went ok, and -1 on error.	958	Passes 0 when everything went ok, and -1 on error.
765		959
766	aio_msync $scalar, $offset = 0, $length = undef, flags = 0,	960	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC,
767	$callback->($status)	961	$callback->($status)
768	This is a rather advanced IO::AIO call, which only works on	962	This is a rather advanced IO::AIO call, which only works on
769	mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it	963	mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
770	also works on data scalars managed by the Sys::Mmap or Mmap modules,	964	also works on data scalars managed by the Sys::Mmap or Mmap modules,
771	note that the scalar must only be modified in-place while an aio	965	note that the scalar must only be modified in-place while an aio
…		…
773		967
774	It calls the "msync" function of your OS, if available, with the	968	It calls the "msync" function of your OS, if available, with the
775	memory area starting at $offset in the string and ending $length	969	memory area starting at $offset in the string and ending $length
776	bytes later. If $length is negative, counts from the end, and if	970	bytes later. If $length is negative, counts from the end, and if
777	$length is "undef", then it goes till the end of the string. The	971	$length is "undef", then it goes till the end of the string. The
778	flags can be a combination of "IO::AIO::MS_ASYNC",	972	flags can be either "IO::AIO::MS_ASYNC" or "IO::AIO::MS_SYNC", plus
779	"IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".	973	an optional "IO::AIO::MS_INVALIDATE".
780		974
781	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,	975	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
782	$callback->($status)	976	$callback->($status)
783	This is a rather advanced IO::AIO call, which works best on	977	This is a rather advanced IO::AIO call, which works best on
784	mmap(2)ed scalars.	978	mmap(2)ed scalars.
785		979
786	It touches (reads or writes) all memory pages in the specified range	980	It touches (reads or writes) all memory pages in the specified range
787	inside the scalar. All caveats and parameters are the same as for	981	inside the scalar. All caveats and parameters are the same as for
788	"aio_msync", above, except for flags, which must be either 0 (which	982	"aio_msync", above, except for flags, which must be either 0 (which
789	reads all pages and ensures they are instantiated) or	983	reads all pages and ensures they are instantiated) or
790	"IO::AIO::MT_MODIFY", which modifies the memory page s(by reading	984	"IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
791	and writing an octet from it, which dirties the page).	985	and writing an octet from it, which dirties the page).
792		986
793	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	987	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
794	This is a rather advanced IO::AIO call, which works best on	988	This is a rather advanced IO::AIO call, which works best on
795	mmap(2)ed scalars.	989	mmap(2)ed scalars.
…		…
827		1021
828	Example: asynchronously lock all current and future pages into	1022	Example: asynchronously lock all current and future pages into
829	memory.	1023	memory.
830		1024
831	aio_mlockall IO::AIO::MCL_FUTURE;	1025	aio_mlockall IO::AIO::MCL_FUTURE;
		1026
		1027	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1028	Queries the extents of the given file (by calling the Linux "FIEMAP"
		1029	ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
		1030	details). If the ioctl is not available on your OS, then this
		1031	request will fail with "ENOSYS".
		1032
		1033	$start is the starting offset to query extents for, $length is the
		1034	size of the range to query - if it is "undef", then the whole file
		1035	will be queried.
		1036
		1037	$flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
		1038	"IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
		1039	also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
		1040	query the data portion.
		1041
		1042	$count is the maximum number of extent records to return. If it is
		1043	"undef", then IO::AIO queries all extents of the range. As a very
		1044	special case, if it is 0, then the callback receives the number of
		1045	extents instead of the extents themselves (which is unreliable, see
		1046	below).
		1047
		1048	If an error occurs, the callback receives no arguments. The special
		1049	"errno" value "IO::AIO::EBADR" is available to test for flag errors.
		1050
		1051	Otherwise, the callback receives an array reference with extent
		1052	structures. Each extent structure is an array reference itself, with
		1053	the following members:
		1054
		1055	[$logical, $physical, $length, $flags]
		1056
		1057	Flags is any combination of the following flag values (typically
		1058	either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
		1059
		1060	"IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
		1061	"IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
		1062	"IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
		1063	"IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
		1064	"IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
		1065	"IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
		1066	"IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
		1067	or "IO::AIO::FIEMAP_EXTENT_SHARED".
		1068
		1069	At the time of this writing (Linux 3.2), this request is unreliable
		1070	unless $count is "undef", as the kernel has all sorts of bugs
		1071	preventing it to return all extents of a range for files with a
		1072	large number of extents. The code (only) works around all these
		1073	issues if $count is "undef".
832		1074
833	aio_group $callback->(...)	1075	aio_group $callback->(...)
834	This is a very special aio request: Instead of doing something, it	1076	This is a very special aio request: Instead of doing something, it
835	is a container for other aio requests, which is useful if you want	1077	is a container for other aio requests, which is useful if you want
836	to bundle many requests into a single, composite, request with a	1078	to bundle many requests into a single, composite, request with a
…		…
870	While it is theoretically handy to have simple I/O scheduling	1112	While it is theoretically handy to have simple I/O scheduling
871	requests like sleep and file handle readable/writable, the overhead	1113	requests like sleep and file handle readable/writable, the overhead
872	this creates is immense (it blocks a thread for a long time) so do	1114	this creates is immense (it blocks a thread for a long time) so do
873	not use this function except to put your application under	1115	not use this function except to put your application under
874	artificial I/O pressure.	1116	artificial I/O pressure.
		1117
		1118	IO::AIO::WD - multiple working directories
		1119	Your process only has one current working directory, which is used by
		1120	all threads. This makes it hard to use relative paths (some other
		1121	component could call "chdir" at any time, and it is hard to control when
		1122	the path will be used by IO::AIO).
		1123
		1124	One solution for this is to always use absolute paths. This usually
		1125	works, but can be quite slow (the kernel has to walk the whole path on
		1126	every access), and can also be a hassle to implement.
		1127
		1128	Newer POSIX systems have a number of functions (openat, fdopendir,
		1129	futimensat and so on) that make it possible to specify working
		1130	directories per operation.
		1131
		1132	For portability, and because the clowns who "designed", or shall I
		1133	write, perpetrated this new interface were obviously half-drunk, this
		1134	abstraction cannot be perfect, though.
		1135
		1136	IO::AIO allows you to convert directory paths into a so-called
		1137	IO::AIO::WD object. This object stores the canonicalised, absolute
		1138	version of the path, and on systems that allow it, also a directory file
		1139	descriptor.
		1140
		1141	Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
		1142	or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
		1143	object and a pathname instead (or the IO::AIO::WD object alone, which
		1144	gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
		1145	IO::AIO::WD object is ignored, otherwise the pathname is resolved
		1146	relative to that IO::AIO::WD object.
		1147
		1148	For example, to get a wd object for /etc and then stat passwd inside,
		1149	you would write:
		1150
		1151	aio_wd "/etc", sub {
		1152	my $etcdir = shift;
		1153
		1154	# although $etcdir can be undef on error, there is generally no reason
		1155	# to check for errors here, as aio_stat will fail with ENOENT
		1156	# when $etcdir is undef.
		1157
		1158	aio_stat [$etcdir, "passwd"], sub {
		1159	# yay
		1160	};
		1161	};
		1162
		1163	The fact that "aio_wd" is a request and not a normal function shows that
		1164	creating an IO::AIO::WD object is itself a potentially blocking
		1165	operation, which is why it is done asynchronously.
		1166
		1167	To stat the directory obtained with "aio_wd" above, one could write
		1168	either of the following three request calls:
		1169
		1170	aio_lstat "/etc" , sub { ... # pathname as normal string
		1171	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1172	aio_lstat $wd , sub { ... # shorthand for the previous
		1173
		1174	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1175	object and the pathname string, so you could write the following without
		1176	causing any issues due to $path getting reused:
		1177
		1178	my $path = [$wd, undef];
		1179
		1180	for my $name (qw(abc def ghi)) {
		1181	$path->[1] = $name;
		1182	aio_stat $path, sub {
		1183	# ...
		1184	};
		1185	}
		1186
		1187	There are some caveats: when directories get renamed (or deleted), the
		1188	pathname string doesn't change, so will point to the new directory (or
		1189	nowhere at all), while the directory fd, if available on the system,
		1190	will still point to the original directory. Most functions accepting a
		1191	pathname will use the directory fd on newer systems, and the string on
		1192	older systems. Some functions (such as "aio_realpath") will always rely
		1193	on the string form of the pathname.
		1194
		1195	So this functionality is mainly useful to get some protection against
		1196	"chdir", to easily get an absolute path out of a relative path for
		1197	future reference, and to speed up doing many operations in the same
		1198	directory (e.g. when stat'ing all files in a directory).
		1199
		1200	The following functions implement this working directory abstraction:
		1201
		1202	aio_wd $pathname, $callback->($wd)
		1203	Asynchonously canonicalise the given pathname and convert it to an
		1204	IO::AIO::WD object representing it. If possible and supported on the
		1205	system, also open a directory fd to speed up pathname resolution
		1206	relative to this working directory.
		1207
		1208	If something goes wrong, then "undef" is passwd to the callback
		1209	instead of a working directory object and $! is set appropriately.
		1210	Since passing "undef" as working directory component of a pathname
		1211	fails the request with "ENOENT", there is often no need for error
		1212	checking in the "aio_wd" callback, as future requests using the
		1213	value will fail in the expected way.
		1214
		1215	IO::AIO::CWD
		1216	This is a compiletime constant (object) that represents the process
		1217	current working directory.
		1218
		1219	Specifying this object as working directory object for a pathname is
		1220	as if the pathname would be specified directly, without a directory
		1221	object. For example, these calls are functionally identical:
		1222
		1223	aio_stat "somefile", sub { ... };
		1224	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1225
		1226	To recover the path associated with an IO::AIO::WD object, you can use
		1227	"aio_realpath":
		1228
		1229	aio_realpath $wd, sub {
		1230	warn "path is $_[0]\n";
		1231	};
		1232
		1233	Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
		1234	sometimes, fall back to using an absolue path.
875		1235
876	IO::AIO::REQ CLASS	1236	IO::AIO::REQ CLASS
877	All non-aggregate "aio_*" functions return an object of this class when	1237	All non-aggregate "aio_*" functions return an object of this class when
878	called in non-void context.	1238	called in non-void context.
879		1239
…		…
979	Sets a feeder/generator on this group: every group can have an	1339	Sets a feeder/generator on this group: every group can have an
980	attached generator that generates requests if idle. The idea behind	1340	attached generator that generates requests if idle. The idea behind
981	this is that, although you could just queue as many requests as you	1341	this is that, although you could just queue as many requests as you
982	want in a group, this might starve other requests for a potentially	1342	want in a group, this might starve other requests for a potentially
983	long time. For example, "aio_scandir" might generate hundreds of	1343	long time. For example, "aio_scandir" might generate hundreds of
984	thousands "aio_stat" requests, delaying any later requests for a	1344	thousands of "aio_stat" requests, delaying any later requests for a
985	long time.	1345	long time.
986		1346
987	To avoid this, and allow incremental generation of requests, you can	1347	To avoid this, and allow incremental generation of requests, you can
988	instead a group and set a feeder on it that generates those	1348	instead a group and set a feeder on it that generates those
989	requests. The feed callback will be called whenever there are few	1349	requests. The feed callback will be called whenever there are few
…		…
1031	results.	1391	results.
1032		1392
1033	See "poll_cb" for an example.	1393	See "poll_cb" for an example.
1034		1394
1035	IO::AIO::poll_cb	1395	IO::AIO::poll_cb
1036	Process some outstanding events on the result pipe. You have to call	1396	Process some requests that have reached the result phase (i.e. they
		1397	have been executed but the results are not yet reported). You have
		1398	to call this "regularly" to finish outstanding requests.
		1399
1037	this regularly. Returns 0 if all events could be processed (or there	1400	Returns 0 if all events could be processed (or there were no events
1038	were no events to process), or -1 if it returned earlier for	1401	to process), or -1 if it returned earlier for whatever reason.
1039	whatever reason. Returns immediately when no events are outstanding.	1402	Returns immediately when no events are outstanding. The amount of
1040	The amount of events processed depends on the settings of	1403	events processed depends on the settings of "IO::AIO::max_poll_req",
1041	"IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".	1404	"IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
1042		1405
1043	If not all requests were processed for whatever reason, the	1406	If not all requests were processed for whatever reason, the poll
1044	filehandle will still be ready when "poll_cb" returns, so normally	1407	file descriptor will still be ready when "poll_cb" returns, so
1045	you don't have to do anything special to have it called later.	1408	normally you don't have to do anything special to have it called
		1409	later.
1046		1410
1047	Apart from calling "IO::AIO::poll_cb" when the event filehandle	1411	Apart from calling "IO::AIO::poll_cb" when the event filehandle
1048	becomes ready, it can be beneficial to call this function from loops	1412	becomes ready, it can be beneficial to call this function from loops
1049	which submit a lot of requests, to make sure the results get	1413	which submit a lot of requests, to make sure the results get
1050	processed when they become available and not just when the loop is	1414	processed when they become available and not just when the loop is
…		…
1058	Event->io (fd => IO::AIO::poll_fileno,	1422	Event->io (fd => IO::AIO::poll_fileno,
1059	poll => 'r', async => 1,	1423	poll => 'r', async => 1,
1060	cb => \&IO::AIO::poll_cb);	1424	cb => \&IO::AIO::poll_cb);
1061		1425
1062	IO::AIO::poll_wait	1426	IO::AIO::poll_wait
1063	If there are any outstanding requests and none of them in the result	1427	Wait until either at least one request is in the result phase or no
1064	phase, wait till the result filehandle becomes ready for reading	1428	requests are outstanding anymore.
1065	(simply does a "select" on the filehandle. This is useful if you	1429
1066	want to synchronously wait for some requests to finish).	1430	This is useful if you want to synchronously wait for some requests
		1431	to become ready, without actually handling them.
1067		1432
1068	See "nreqs" for an example.	1433	See "nreqs" for an example.
1069		1434
1070	IO::AIO::poll	1435	IO::AIO::poll
1071	Waits until some requests have been handled.	1436	Waits until some requests have been handled.
…		…
1170	IO::AIO::idle_timeout $seconds	1535	IO::AIO::idle_timeout $seconds
1171	Sets the minimum idle timeout (default 10) after which worker	1536	Sets the minimum idle timeout (default 10) after which worker
1172	threads are allowed to exit. SEe "IO::AIO::max_idle".	1537	threads are allowed to exit. SEe "IO::AIO::max_idle".
1173		1538
1174	IO::AIO::max_outstanding $maxreqs	1539	IO::AIO::max_outstanding $maxreqs
		1540	Sets the maximum number of outstanding requests to $nreqs. If you do
		1541	queue up more than this number of requests, the next call to
		1542	"IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
		1543	"IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
		1544	no longer exceeded.
		1545
		1546	In other words, this setting does not enforce a queue limit, but can
		1547	be used to make poll functions block if the limit is exceeded.
		1548
1175	This is a very bad function to use in interactive programs because	1549	This is a very bad function to use in interactive programs because
1176	it blocks, and a bad way to reduce concurrency because it is	1550	it blocks, and a bad way to reduce concurrency because it is
1177	inexact: Better use an "aio_group" together with a feed callback.	1551	inexact: Better use an "aio_group" together with a feed callback.
1178		1552
1179	Sets the maximum number of outstanding requests to $nreqs. If you do	1553	Its main use is in scripts without an event loop - when you want to
1180	queue up more than this number of requests, the next call to the	1554	stat a lot of files, you can write something like this:
1181	"poll_cb" (and "poll_some" and other functions calling "poll_cb")
1182	function will block until the limit is no longer exceeded.
1183		1555
1184	The default value is very large, so there is no practical limit on	1556	IO::AIO::max_outstanding 32;
		1557
		1558	for my $path (...) {
		1559	aio_stat $path , ...;
		1560	IO::AIO::poll_cb;
		1561	}
		1562
		1563	IO::AIO::flush;
		1564
		1565	The call to "poll_cb" inside the loop will normally return
		1566	instantly, but as soon as more thna 32 reqeusts are in-flight, it
		1567	will block until some requests have been handled. This keeps the
		1568	loop from pushing a large number of "aio_stat" requests onto the
		1569	queue.
		1570
		1571	The default value for "max_outstanding" is very large, so there is
1185	the number of outstanding requests.	1572	no practical limit on the number of outstanding requests.
1186
1187	You can still queue as many requests as you want. Therefore,
1188	"max_outstanding" is mainly useful in simple scripts (with low
1189	values) or as a stop gap to shield against fatal memory overflow
1190	(with large values).
1191		1573
1192	STATISTICAL INFORMATION	1574	STATISTICAL INFORMATION
1193	IO::AIO::nreqs	1575	IO::AIO::nreqs
1194	Returns the number of requests currently in the ready, execute or	1576	Returns the number of requests currently in the ready, execute or
1195	pending states (i.e. for which their callback has not been invoked	1577	pending states (i.e. for which their callback has not been invoked
…		…
1207	IO::AIO::npending	1589	IO::AIO::npending
1208	Returns the number of requests currently in the pending state	1590	Returns the number of requests currently in the pending state
1209	(executed, but not yet processed by poll_cb).	1591	(executed, but not yet processed by poll_cb).
1210		1592
1211	MISCELLANEOUS FUNCTIONS	1593	MISCELLANEOUS FUNCTIONS
1212	IO::AIO implements some functions that might be useful, but are not	1594	IO::AIO implements some functions that are useful when you want to use
1213	asynchronous.	1595	some "Advanced I/O" function not available to in Perl, without going the
		1596	"Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
		1597	counterpart.
		1598
		1599	$numfd = IO::AIO::get_fdlimit
		1600	This function is EXPERIMENTAL and subject to change.
		1601
		1602	Tries to find the current file descriptor limit and returns it, or
		1603	"undef" and sets $! in case of an error. The limit is one larger
		1604	than the highest valid file descriptor number.
		1605
		1606	IO::AIO::min_fdlimit [$numfd]
		1607	This function is EXPERIMENTAL and subject to change.
		1608
		1609	Try to increase the current file descriptor limit(s) to at least
		1610	$numfd by changing the soft or hard file descriptor resource limit.
		1611	If $numfd is missing, it will try to set a very high limit, although
		1612	this is not recommended when you know the actual minimum that you
		1613	require.
		1614
		1615	If the limit cannot be raised enough, the function makes a
		1616	best-effort attempt to increase the limit as much as possible, using
		1617	various tricks, while still failing. You can query the resulting
		1618	limit using "IO::AIO::get_fdlimit".
		1619
		1620	If an error occurs, returns "undef" and sets $!, otherwise returns
		1621	true.
1214		1622
1215	IO::AIO::sendfile $ofh, $ifh, $offset, $count	1623	IO::AIO::sendfile $ofh, $ifh, $offset, $count
1216	Calls the "eio_sendfile_sync" function, which is like	1624	Calls the "eio_sendfile_sync" function, which is like
1217	"aio_sendfile", but is blocking (this makes most sense if you know	1625	"aio_sendfile", but is blocking (this makes most sense if you know
1218	the input data is likely cached already and the output filehandle is	1626	the input data is likely cached already and the output filehandle is
…		…
1220		1628
1221	Returns the number of bytes copied, or -1 on error.	1629	Returns the number of bytes copied, or -1 on error.
1222		1630
1223	IO::AIO::fadvise $fh, $offset, $len, $advice	1631	IO::AIO::fadvise $fh, $offset, $len, $advice
1224	Simply calls the "posix_fadvise" function (see its manpage for	1632	Simply calls the "posix_fadvise" function (see its manpage for
1225	details). The following advice constants are avaiable:	1633	details). The following advice constants are available:
1226	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",	1634	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1227	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",	1635	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1228	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".	1636	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1229		1637
1230	On systems that do not implement "posix_fadvise", this function	1638	On systems that do not implement "posix_fadvise", this function
1231	returns ENOSYS, otherwise the return value of "posix_fadvise".	1639	returns ENOSYS, otherwise the return value of "posix_fadvise".
1232		1640
1233	IO::AIO::madvise $scalar, $offset, $len, $advice	1641	IO::AIO::madvise $scalar, $offset, $len, $advice
1234	Simply calls the "posix_madvise" function (see its manpage for	1642	Simply calls the "posix_madvise" function (see its manpage for
1235	details). The following advice constants are avaiable:	1643	details). The following advice constants are available:
1236	"IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",	1644	"IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1237	"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",	1645	"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1238	"IO::AIO::MADV_DONTNEED".	1646	"IO::AIO::MADV_DONTNEED".
1239		1647
		1648	If $offset is negative, counts from the end. If $length is negative,
		1649	the remaining length of the $scalar is used. If possible, $length
		1650	will be reduced to fit into the $scalar.
		1651
1240	On systems that do not implement "posix_madvise", this function	1652	On systems that do not implement "posix_madvise", this function
1241	returns ENOSYS, otherwise the return value of "posix_madvise".	1653	returns ENOSYS, otherwise the return value of "posix_madvise".
1242		1654
1243	IO::AIO::mprotect $scalar, $offset, $len, $protect	1655	IO::AIO::mprotect $scalar, $offset, $len, $protect
1244	Simply calls the "mprotect" function on the preferably AIO::mmap'ed	1656	Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1245	$scalar (see its manpage for details). The following protect	1657	$scalar (see its manpage for details). The following protect
1246	constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",	1658	constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1247	"IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".	1659	"IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
		1660
		1661	If $offset is negative, counts from the end. If $length is negative,
		1662	the remaining length of the $scalar is used. If possible, $length
		1663	will be reduced to fit into the $scalar.
1248		1664
1249	On systems that do not implement "mprotect", this function returns	1665	On systems that do not implement "mprotect", this function returns
1250	ENOSYS, otherwise the return value of "mprotect".	1666	ENOSYS, otherwise the return value of "mprotect".
1251		1667
1252	IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	1668	IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1253	Memory-maps a file (or anonymous memory range) and attaches it to	1669	Memory-maps a file (or anonymous memory range) and attaches it to
1254	the given $scalar, which will act like a string scalar.	1670	the given $scalar, which will act like a string scalar. Returns true
		1671	on success, and false otherwise.
1255		1672
		1673	The scalar must exist, but its contents do not matter - this means
		1674	you cannot use a nonexistant array or hash element. When in doubt,
		1675	"undef" the scalar first.
		1676
1256	The only operations allowed on the scalar are "substr"/"vec" that	1677	The only operations allowed on the mmapped scalar are
1257	don't change the string length, and most read-only operations such	1678	"substr"/"vec", which don't change the string length, and most
1258	as copying it or searching it with regexes and so on.	1679	read-only operations such as copying it or searching it with regexes
		1680	and so on.
1259		1681
1260	Anything else is unsafe and will, at best, result in memory leaks.	1682	Anything else is unsafe and will, at best, result in memory leaks.
1261		1683
1262	The memory map associated with the $scalar is automatically removed	1684	The memory map associated with the $scalar is automatically removed
1263	when the $scalar is destroyed, or when the "IO::AIO::mmap" or	1685	when the $scalar is undef'd or destroyed, or when the
1264	"IO::AIO::munmap" functions are called.	1686	"IO::AIO::mmap" or "IO::AIO::munmap" functions are called on it.
1265		1687
1266	This calls the "mmap"(2) function internally. See your system's	1688	This calls the "mmap"(2) function internally. See your system's
1267	manual page for details on the $length, $prot and $flags parameters.	1689	manual page for details on the $length, $prot and $flags parameters.
1268		1690
1269	The $length must be larger than zero and smaller than the actual	1691	The $length must be larger than zero and smaller than the actual
…		…
1273	"IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or	1695	"IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1274	"IO::AIO::PROT_WRITE",	1696	"IO::AIO::PROT_WRITE",
1275		1697
1276	$flags can be a combination of "IO::AIO::MAP_SHARED" or	1698	$flags can be a combination of "IO::AIO::MAP_SHARED" or
1277	"IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when	1699	"IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1278	not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"	1700	not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1279	(which is set to "MAP_ANON" if your system only provides this	1701	"MAP_ANON" if your system only provides this constant),
		1702	"IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
1280	constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",	1703	"IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
		1704	"IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
1281	"IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or	1705	"IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB" or
1282	"IO::AIO::MAP_NONBLOCK"	1706	"IO::AIO::MAP_STACK".
1283		1707
1284	If $fh is "undef", then a file descriptor of -1 is passed.	1708	If $fh is "undef", then a file descriptor of -1 is passed.
1285		1709
1286	$offset is the offset from the start of the file - it generally must	1710	$offset is the offset from the start of the file - it generally must
1287	be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.	1711	be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
…		…
1309	IO::AIO::munlockall	1733	IO::AIO::munlockall
1310	Calls the "munlockall" function.	1734	Calls the "munlockall" function.
1311		1735
1312	On systems that do not implement "munlockall", this function returns	1736	On systems that do not implement "munlockall", this function returns
1313	ENOSYS, otherwise the return value of "munlockall".	1737	ENOSYS, otherwise the return value of "munlockall".
		1738
		1739	IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		1740	Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
		1741	$w_off are "undef", then "NULL" is passed for these, otherwise they
		1742	should be the file offset.
		1743
		1744	$r_fh and $w_fh should not refer to the same file, as splice might
		1745	silently corrupt the data in this case.
		1746
		1747	The following symbol flag values are available:
		1748	"IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
		1749	"IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
		1750
		1751	See the splice(2) manpage for details.
		1752
		1753	IO::AIO::tee $r_fh, $w_fh, $length, $flags
		1754	Calls the GNU/Linux tee(2) syscall, see its manpage and the
		1755	description for "IO::AIO::splice" above for details.
		1756
		1757	$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		1758	Attempts to query or change the pipe buffer size. Obviously works
		1759	only on pipes, and currently works only on GNU/Linux systems, and
		1760	fails with -1/"ENOSYS" everywhere else. If anybody knows how to
		1761	influence pipe buffer size on other systems, drop me a note.
		1762
		1763	($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		1764	This is a direct interface to the Linux pipe2(2) system call. If
		1765	$flags is missing or 0, then this should be the same as a call to
		1766	perl's built-in "pipe" function and create a new pipe, and works on
		1767	systems that lack the pipe2 syscall. On win32, this case invokes
		1768	"_pipe (..., 4096, O_BINARY)".
		1769
		1770	If $flags is non-zero, it tries to invoke the pipe2 system call with
		1771	the given flags (Linux 2.6.27, glibc 2.9).
		1772
		1773	On success, the read and write file handles are returned.
		1774
		1775	On error, nothing will be returned. If the pipe2 syscall is missing
		1776	and $flags is non-zero, fails with "ENOSYS".
		1777
		1778	Please refer to pipe2(2) for more info on the $flags, but at the
		1779	time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
		1780	and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
		1781	supported.
		1782
		1783	Example: create a pipe race-free w.r.t. threads and fork:
		1784
		1785	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		1786	or die "pipe2: $!\n";
		1787
		1788	$fh = IO::AIO::eventfd [$initval, [$flags]]
		1789	This is a direct interface to the Linux eventfd(2) system call. The
		1790	(unhelpful) defaults for $initval and $flags are 0 for both.
		1791
		1792	On success, the new eventfd filehandle is returned, otherwise
		1793	returns "undef". If the eventfd syscall is missing, fails with
		1794	"ENOSYS".
		1795
		1796	Please refer to eventfd(2) for more info on this call.
		1797
		1798	The following symbol flag values are available:
		1799	"IO::AIO::EFD_CLOEXEC", "IO::AIO::EFD_NONBLOCK" and
		1800	"IO::AIO::EFD_SEMAPHORE" (Linux 2.6.30).
		1801
		1802	Example: create a new eventfd filehandle:
		1803
		1804	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		1805	or die "eventfd: $!\n";
		1806
		1807	$fh = IO::AIO::timerfd_create $clockid[, $flags]
		1808	This is a direct interface to the Linux timerfd_create(2) system
		1809	call. The (unhelpful) default for $flags is 0.
		1810
		1811	On success, the new timerfd filehandle is returned, otherwise
		1812	returns "undef". If the eventfd syscall is missing, fails with
		1813	"ENOSYS".
		1814
		1815	Please refer to timerfd_create(2) for more info on this call.
		1816
		1817	The following $clockid values are available:
		1818	"IO::AIO::CLOCK_REALTIME", "IO::AIO::CLOCK_MONOTONIC"
		1819	"IO::AIO::CLOCK_CLOCK_BOOTTIME" (Linux 3.15)
		1820	"IO::AIO::CLOCK_CLOCK_REALTIME_ALARM" (Linux 3.11) and
		1821	"IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM" (Linux 3.11).
		1822
		1823	The following $flags values are available (Linux 2.6.27):
		1824	"IO::AIO::TFD_NONBLOCK" and "IO::AIO::TFD_CLOEXEC".
		1825
		1826	Example: create a new timerfd and set it to one-second repeated
		1827	alarms, then wait for two alarms:
		1828
		1829	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		1830	or die "timerfd_create: $!\n";
		1831
		1832	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		1833	or die "timerfd_settime: $!\n";
		1834
		1835	for (1..2) {
		1836	8 == sysread $fh, my $buf, 8
		1837	or die "timerfd read failure\n";
		1838
		1839	printf "number of expirations (likely 1): %d\n",
		1840	unpack "Q", $buf;
		1841	}
		1842
		1843	($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags,
		1844	$new_interval, $nbw_value
		1845	This is a direct interface to the Linux timerfd_settime(2) system
		1846	call. Please refer to its manpage for more info on this call.
		1847
		1848	The new itimerspec is specified using two (possibly fractional)
		1849	second values, $new_interval and $new_value).
		1850
		1851	On success, the current interval and value are returned (as per
		1852	"timerfd_gettime"). On failure, the empty list is returned.
		1853
		1854	The following $flags values are available:
		1855	"IO::AIO::TFD_TIMER_ABSTIME" and "IO::AIO::TFD_TIMER_CANCEL_ON_SET".
		1856
		1857	See "IO::AIO::timerfd_create" for a full example.
		1858
		1859	($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		1860	This is a direct interface to the Linux timerfd_gettime(2) system
		1861	call. Please refer to its manpage for more info on this call.
		1862
		1863	On success, returns the current values of interval and value for the
		1864	given timerfd (as potentially fractional second values). On failure,
		1865	the empty list is returned.
1314		1866
1315	EVENT LOOP INTEGRATION	1867	EVENT LOOP INTEGRATION
1316	It is recommended to use AnyEvent::AIO to integrate IO::AIO	1868	It is recommended to use AnyEvent::AIO to integrate IO::AIO
1317	automatically into many event loops:	1869	automatically into many event loops:
1318		1870
…		…
1341	# Danga::Socket integration	1893	# Danga::Socket integration
1342	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	1894	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1343	\&IO::AIO::poll_cb);	1895	\&IO::AIO::poll_cb);
1344		1896
1345	FORK BEHAVIOUR	1897	FORK BEHAVIOUR
1346	This module should do "the right thing" when the process using it forks:	1898	Usage of pthreads in a program changes the semantics of fork
		1899	considerably. Specifically, only async-safe functions can be called
		1900	after fork. Perl doesn't know about this, so in general, you cannot call
		1901	fork with defined behaviour in perl if pthreads are involved. IO::AIO
		1902	uses pthreads, so this applies, but many other extensions and (for
		1903	inexplicable reasons) perl itself often is linked against pthreads, so
		1904	this limitation applies to quite a lot of perls.
1347		1905
1348	Before the fork, IO::AIO enters a quiescent state where no requests can	1906	This module no longer tries to fight your OS, or POSIX. That means
1349	be added in other threads and no results will be processed. After the	1907	IO::AIO only works in the process that loaded it. Forking is fully
1350	fork the parent simply leaves the quiescent state and continues	1908	supported, but using IO::AIO in the child is not.
1351	request/result processing, while the child frees the request/result
1352	queue (so that the requests started before the fork will only be handled
1353	in the parent). Threads will be started on demand until the limit set in
1354	the parent process has been reached again.
1355		1909
1356	In short: the parent will, after a short pause, continue as if fork had	1910	You might get around by not using IO::AIO before (or after) forking.
1357	not been called, while the child will act as if IO::AIO has not been	1911	You could also try to call the IO::AIO::reinit function in the child:
1358	used yet.	1912
		1913	IO::AIO::reinit
		1914	Abandons all current requests and I/O threads and simply
		1915	reinitialises all data structures. This is not an operation
		1916	supported by any standards, but happens to work on GNU/Linux and
		1917	some newer BSD systems.
		1918
		1919	The only reasonable use for this function is to call it after
		1920	forking, if "IO::AIO" was used in the parent. Calling it while
		1921	IO::AIO is active in the process will result in undefined behaviour.
		1922	Calling it at any time will also result in any undefined (by POSIX)
		1923	behaviour.
		1924
		1925	LINUX-SPECIFIC CALLS
		1926	When a call is documented as "linux-specific" then this means it
		1927	originated on GNU/Linux. "IO::AIO" will usually try to autodetect the
		1928	availability and compatibility of such calls regardless of the platform
		1929	it is compiled on, so platforms such as FreeBSD which often implement
		1930	these calls will work. When in doubt, call them and see if they fail wth
		1931	"ENOSYS".
1359		1932
1360	MEMORY USAGE	1933	MEMORY USAGE
1361	Per-request usage:	1934	Per-request usage:
1362		1935
1363	Each aio request uses - depending on your architecture - around 100-200	1936	Each aio request uses - depending on your architecture - around 100-200
…		…
1374	In the execution phase, some aio requests require more memory for	1947	In the execution phase, some aio requests require more memory for
1375	temporary buffers, and each thread requires a stack and other data	1948	temporary buffers, and each thread requires a stack and other data
1376	structures (usually around 16k-128k, depending on the OS).	1949	structures (usually around 16k-128k, depending on the OS).
1377		1950
1378	KNOWN BUGS	1951	KNOWN BUGS
1379	Known bugs will be fixed in the next release.	1952	Known bugs will be fixed in the next release :)
		1953
		1954	KNOWN ISSUES
		1955	Calls that try to "import" foreign memory areas (such as "IO::AIO::mmap"
		1956	or "IO::AIO::aio_slurp") do not work with generic lvalues, such as
		1957	non-created hash slots or other scalars I didn't think of. It's best to
		1958	avoid such and either use scalar variables or making sure that the
		1959	scalar exists (e.g. by storing "undef") and isn't "funny" (e.g. tied).
		1960
		1961	I am not sure anything can be done about this, so this is considered a
		1962	known issue, rather than a bug.
1380		1963
1381	SEE ALSO	1964	SEE ALSO
1382	AnyEvent::AIO for easy integration into event loops, Coro::AIO for a	1965	AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1383	more natural syntax.	1966	more natural syntax.
1384		1967

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Comparing IO-AIO/README (file contents): Revision 1.47 by root, Fri May 27 00:44:49 2011 UTC vs. Revision 1.59 by root, Tue Feb 20 06:54:47 2018 UTC

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Comparing IO-AIO/README (file contents):
Revision 1.47 by root, Fri May 27 00:44:49 2011 UTC vs.
Revision 1.59 by root, Tue Feb 20 06:54:47 2018 UTC