--- IO-AIO/README 2009/06/27 03:19:27 1.38 +++ IO-AIO/README 2011/07/18 03:09:06 1.49 @@ -4,7 +4,7 @@ SYNOPSIS use IO::AIO; - aio_open "/etc/passwd", O_RDONLY, 0, sub { + aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub { my $fh = shift or die "/etc/passwd: $!"; ... @@ -26,29 +26,6 @@ my $grp = aio_group sub { print "all stats done\n" }; add $grp aio_stat "..." for ...; - # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...) - use AnyEvent::AIO; - - # EV integration - my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb; - - # Event integration - Event->io (fd => IO::AIO::poll_fileno, - poll => 'r', - cb => \&IO::AIO::poll_cb); - - # Glib/Gtk2 integration - add_watch Glib::IO IO::AIO::poll_fileno, - in => sub { IO::AIO::poll_cb; 1 }; - - # Tk integration - Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", - readable => \&IO::AIO::poll_cb); - - # Danga::Socket integration - Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => - \&IO::AIO::poll_cb); - DESCRIPTION This module implements asynchronous I/O using whatever means your operating system supports. It is implemented as an interface to "libeio" @@ -97,7 +74,7 @@ my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb; # queue the request to open /etc/passwd - aio_open "/etc/passwd", O_RDONLY, 0, sub { + aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub { my $fh = shift or die "error while opening: $!"; @@ -170,6 +147,79 @@ either do nothing or result in a runtime error). FUNCTIONS + QUICK OVERVIEW + This section simply lists the prototypes of the most important functions + for quick reference. See the following sections for function-by-function + documentation. + + aio_open $pathname, $flags, $mode, $callback->($fh) + aio_close $fh, $callback->($status) + aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) + aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) + aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) + aio_readahead $fh,$offset,$length, $callback->($retval) + aio_stat $fh_or_path, $callback->($status) + aio_lstat $fh, $callback->($status) + aio_statvfs $fh_or_path, $callback->($statvfs) + aio_utime $fh_or_path, $atime, $mtime, $callback->($status) + aio_chown $fh_or_path, $uid, $gid, $callback->($status) + aio_truncate $fh_or_path, $offset, $callback->($status) + aio_chmod $fh_or_path, $mode, $callback->($status) + aio_unlink $pathname, $callback->($status) + aio_mknod $path, $mode, $dev, $callback->($status) + aio_link $srcpath, $dstpath, $callback->($status) + aio_symlink $srcpath, $dstpath, $callback->($status) + aio_readlink $path, $callback->($link) + aio_realpath $path, $callback->($link) + aio_rename $srcpath, $dstpath, $callback->($status) + aio_mkdir $pathname, $mode, $callback->($status) + aio_rmdir $pathname, $callback->($status) + aio_readdir $pathname, $callback->($entries) + aio_readdirx $pathname, $flags, $callback->($entries, $flags) + IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST + IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN + aio_load $path, $data, $callback->($status) + aio_copy $srcpath, $dstpath, $callback->($status) + aio_move $srcpath, $dstpath, $callback->($status) + aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) + aio_rmtree $path, $callback->($status) + aio_sync $callback->($status) + aio_fsync $fh, $callback->($status) + aio_fdatasync $fh, $callback->($status) + aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) + aio_pathsync $path, $callback->($status) + aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) + aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) + aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status) + aio_mlockall $flags, $callback->($status) + aio_group $callback->(...) + aio_nop $callback->() + + $prev_pri = aioreq_pri [$pri] + aioreq_nice $pri_adjust + + IO::AIO::poll_wait + IO::AIO::poll_cb + IO::AIO::poll + IO::AIO::flush + IO::AIO::max_poll_reqs $nreqs + IO::AIO::max_poll_time $seconds + IO::AIO::min_parallel $nthreads + IO::AIO::max_parallel $nthreads + IO::AIO::max_idle $nthreads + IO::AIO::idle_timeout $seconds + IO::AIO::max_outstanding $maxreqs + IO::AIO::nreqs + IO::AIO::nready + IO::AIO::npending + + IO::AIO::sendfile $ofh, $ifh, $offset, $count + IO::AIO::fadvise $fh, $offset, $len, $advice + IO::AIO::madvise $scalar, $offset, $length, $advice + IO::AIO::mprotect $scalar, $offset, $length, $protect + IO::AIO::munlock $scalar, $offset = 0, $length = undef + IO::AIO::munlockall + AIO REQUEST FUNCTIONS All the "aio_*" calls are more or less thin wrappers around the syscall with the same name (sans "aio_"). The arguments are similar or @@ -250,7 +300,7 @@ Example: - aio_open "/etc/passwd", O_RDONLY, 0, sub { + aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub { if ($_[0]) { print "open successful, fh is $_[0]\n"; ... @@ -259,6 +309,15 @@ } }; + In addition to all the common open modes/flags ("O_RDONLY", + "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and + "O_APPEND"), the following POSIX and non-POSIX constants are + available (missing ones on your system are, as usual, 0): + + "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY", + "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY", + "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT". + aio_close $fh, $callback->($status) Asynchronously close a file and call the callback with the result code. @@ -311,22 +370,43 @@ reading at byte offset $in_offset, and starts writing at the current file offset of $out_fh. Because of that, it is not safe to issue more than one "aio_sendfile" per $out_fh, as they will interfere - with each other. + with each other. The same $in_fh works fine though, as this function + does not move or use the file offset of $in_fh. - This call tries to make use of a native "sendfile" syscall to + Please note that "aio_sendfile" can read more bytes from $in_fh than + are written, and there is no way to find out how many more bytes + have been read from "aio_sendfile" alone, as "aio_sendfile" only + provides the number of bytes written to $out_fh. Only if the result + value equals $length one can assume that $length bytes have been + read. + + Unlike with other "aio_" functions, it makes a lot of sense to use + "aio_sendfile" on non-blocking sockets, as long as one end + (typically the $in_fh) is a file - the file I/O will then be + asynchronous, while the socket I/O will be non-blocking. Note, + however, that you can run into a trap where "aio_sendfile" reads + some data with readahead, then fails to write all data, and when the + socket is ready the next time, the data in the cache is already + lost, forcing "aio_sendfile" to again hit the disk. Explicit + "aio_read" + "aio_write" let's you better control resource usage. + + This call tries to make use of a native "sendfile"-like syscall to provide zero-copy operation. For this to work, $out_fh should refer - to a socket, and $in_fh should refer to mmap'able file. + to a socket, and $in_fh should refer to an mmap'able file. - If the native sendfile call fails or is not implemented, it will be - emulated, so you can call "aio_sendfile" on any type of filehandle - regardless of the limitations of the operating system. - - Please note, however, that "aio_sendfile" can read more bytes from - $in_fh than are written, and there is no way to find out how many - bytes have been read from "aio_sendfile" alone, as "aio_sendfile" - only provides the number of bytes written to $out_fh. Only if the - result value equals $length one can assume that $length bytes have - been read. + If a native sendfile cannot be found or it fails with "ENOSYS", + "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or + "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on + any type of filehandle regardless of the limitations of the + operating system. + + As native sendfile syscalls (as practically any non-POSIX interface + hacked together in a hurry to improve benchmark numbers) tend to be + rather buggy on many systems, this implementation tries to work + around some known bugs in Linux and FreeBSD kernels (probably + others, too), but that might fail, so you really really should check + the return value of "aio_sendfile" - fewre bytes than expected might + have been transferred. aio_readahead $fh,$offset,$length, $callback->($retval) "aio_readahead" populates the page cache with data from a file so @@ -357,6 +437,15 @@ silently truncated unless perl itself is compiled with large file support. + To help interpret the mode and dev/rdev stat values, IO::AIO offers + the following constants and functions (if not implemented, the + constants will be 0 and the functions will either "croak" or fall + back on traditional behaviour). + + "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG", + "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t", + "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor". + Example: Print the length of /etc/passwd: aio_stat "/etc/passwd", sub { @@ -364,6 +453,49 @@ print "size is ", -s _, "\n"; }; + aio_statvfs $fh_or_path, $callback->($statvfs) + Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on + whether a file handle or path was passed. + + On success, the callback is passed a hash reference with the + following members: "bsize", "frsize", "blocks", "bfree", "bavail", + "files", "ffree", "favail", "fsid", "flag" and "namemax". On + failure, "undef" is passed. + + The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY" + and "ST_NOSUID". + + The following non-POSIX IO::AIO::ST_* flag masks are defined to + their correct value when available, or to 0 on systems that do not + support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS", + "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE", + "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME". + + Example: stat "/wd" and dump out the data if successful. + + aio_statvfs "/wd", sub { + my $f = $_[0] + or die "statvfs: $!"; + + use Data::Dumper; + say Dumper $f; + }; + + # result: + { + bsize => 1024, + bfree => 4333064312, + blocks => 10253828096, + files => 2050765568, + flag => 4096, + favail => 2042092649, + bavail => 4333064312, + ffree => 2042092649, + namemax => 255, + frsize => 1024, + fsid => 1810 + } + aio_utime $fh_or_path, $atime, $mtime, $callback->($status) Works like perl's "utime" function (including the special case of $atime and $mtime being undef). Fractional times are supported if @@ -411,6 +543,9 @@ aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... + See "aio_stat" for info about some potentially helpful extra + constants and functions. + aio_link $srcpath, $dstpath, $callback->($status) Asynchronously create a new link to the existing object at $srcpath at the path $dstpath and call the callback with the result code. @@ -425,6 +560,14 @@ the callback. If an error occurs, nothing or undef gets passed to the callback. + aio_realpath $path, $callback->($path) + Asynchronously make the path absolute and resolve any symlinks in + $path. The resulting path only consists of directories (Same as + Cwd::realpath). + + This request can be used to get the absolute path of the current + working directory by passing it a path of . (a single dot). + aio_rename $srcpath, $dstpath, $callback->($status) Asynchronously rename the object at $srcpath to $dstpath, just as rename(2) and call the callback with the result code. @@ -456,9 +599,9 @@ modified): IO::AIO::READDIR_DENTS - When this flag is off, then the callback gets an arrayref with - of names only (as with "aio_readdir"), otherwise it gets an - arrayref with "[$name, $type, $inode]" arrayrefs, each + When this flag is off, then the callback gets an arrayref + consisting of names only (as with "aio_readdir"), otherwise it + gets an arrayref with "[$name, $type, $inode]" arrayrefs, each describing a single directory entry in more detail. $name is the name of the entry. @@ -481,14 +624,15 @@ IO::AIO::READDIR_DIRS_FIRST When this flag is set, then the names will be returned in an - order where likely directories come first. This is useful when - you need to quickly find directories, or you want to find all - directories while avoiding to stat() each entry. + order where likely directories come first, in optimal stat + order. This is useful when you need to quickly find directories, + or you want to find all directories while avoiding to stat() + each entry. If the system returns type information in readdir, then this is used to find directories directly. Otherwise, likely directories - are files beginning with ".", or otherwise files with no dots, - of which files with short names are tried first. + are names beginning with ".", or otherwise names with no dots, + of which names with short names are tried first. IO::AIO::READDIR_STAT_ORDER When this flag is set, then the names will be returned in an @@ -514,7 +658,7 @@ aio_copy $srcpath, $dstpath, $callback->($status) Try to copy the *file* (directories not supported as either source or destination) from $srcpath to $dstpath and call the callback with - the 0 (error) or -1 ok. + a status of 0 (ok) or -1 (error, see $!). This is a composite request that creates the destination file with mode 0200 and copies the contents of the source file into it using @@ -528,7 +672,7 @@ aio_move $srcpath, $dstpath, $callback->($status) Try to move the *file* (directories not supported as either source or destination) from $srcpath to $dstpath and call the callback with - the 0 (error) or -1 ok. + a status of 0 (ok) or -1 (error, see $!). This is a composite request that tries to rename(2) the file first; if rename fails with "EXDEV", it copies the file with "aio_copy" @@ -633,8 +777,78 @@ directory changes get written to disc. It works for anything that can be opened for read-only, not just directories. + Future versions of this function might fall back to other methods + when "fsync" on the directory fails (such as calling "sync"). + Passes 0 when everything went ok, and -1 on error. + aio_msync $scalar, $offset = 0, $length = undef, flags = 0, + $callback->($status) + This is a rather advanced IO::AIO call, which only works on + mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it + also works on data scalars managed by the Sys::Mmap or Mmap modules, + note that the scalar must only be modified in-place while an aio + operation is pending on it). + + It calls the "msync" function of your OS, if available, with the + memory area starting at $offset in the string and ending $length + bytes later. If $length is negative, counts from the end, and if + $length is "undef", then it goes till the end of the string. The + flags can be a combination of "IO::AIO::MS_ASYNC", + "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC". + + aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, + $callback->($status) + This is a rather advanced IO::AIO call, which works best on + mmap(2)ed scalars. + + It touches (reads or writes) all memory pages in the specified range + inside the scalar. All caveats and parameters are the same as for + "aio_msync", above, except for flags, which must be either 0 (which + reads all pages and ensures they are instantiated) or + "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading + and writing an octet from it, which dirties the page). + + aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status) + This is a rather advanced IO::AIO call, which works best on + mmap(2)ed scalars. + + It reads in all the pages of the underlying storage into memory (if + any) and locks them, so they are not getting swapped/paged out or + removed. + + If $length is undefined, then the scalar will be locked till the + end. + + On systems that do not implement "mlock", this function returns -1 + and sets errno to "ENOSYS". + + Note that the corresponding "munlock" is synchronous and is + documented under "MISCELLANEOUS FUNCTIONS". + + Example: open a file, mmap and mlock it - both will be undone when + $data gets destroyed. + + open my $fh, "<", $path or die "$path: $!"; + my $data; + IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh; + aio_mlock $data; # mlock in background + + aio_mlockall $flags, $callback->($status) + Calls the "mlockall" function with the given $flags (a combination + of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE"). + + On systems that do not implement "mlockall", this function returns + -1 and sets errno to "ENOSYS". + + Note that the corresponding "munlockall" is synchronous and is + documented under "MISCELLANEOUS FUNCTIONS". + + Example: asynchronously lock all current and future pages into + memory. + + aio_mlockall IO::AIO::MCL_FUTURE; + aio_group $callback->(...) This is a very special aio request: Instead of doing something, it is a container for other aio requests, which is useful if you want @@ -760,6 +974,9 @@ request itself. Useful when you queued a lot of events but got a result early. + The group request will finish normally (you cannot add requests to + the group). + $grp->result (...) Set the result value(s) that will be passed to the group callback when all subrequests have finished and set the groups errno to the @@ -836,16 +1053,23 @@ IO::AIO::poll_cb Process some outstanding events on the result pipe. You have to call - this regularly. Returns 0 if all events could be processed, or -1 if - it returned earlier for whatever reason. Returns immediately when no - events are outstanding. The amount of events processed depends on - the settings of "IO::AIO::max_poll_req" and - "IO::AIO::max_poll_time". + this regularly. Returns 0 if all events could be processed (or there + were no events to process), or -1 if it returned earlier for + whatever reason. Returns immediately when no events are outstanding. + The amount of events processed depends on the settings of + "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". If not all requests were processed for whatever reason, the filehandle will still be ready when "poll_cb" returns, so normally you don't have to do anything special to have it called later. + Apart from calling "IO::AIO::poll_cb" when the event filehandle + becomes ready, it can be beneficial to call this function from loops + which submit a lot of requests, to make sure the results get + processed when they become available and not just when the loop is + finished and the event loop takes over again. This function returns + very fast when there are no outstanding requests. + Example: Install an Event watcher that automatically calls IO::AIO::poll_cb with high priority (more examples can be found in the SYNOPSIS section, at the top of this document): @@ -854,6 +1078,30 @@ poll => 'r', async => 1, cb => \&IO::AIO::poll_cb); + IO::AIO::poll_wait + If there are any outstanding requests and none of them in the result + phase, wait till the result filehandle becomes ready for reading + (simply does a "select" on the filehandle. This is useful if you + want to synchronously wait for some requests to finish). + + See "nreqs" for an example. + + IO::AIO::poll + Waits until some requests have been handled. + + Returns the number of requests processed, but is otherwise strictly + equivalent to: + + IO::AIO::poll_wait, IO::AIO::poll_cb + + IO::AIO::flush + Wait till all outstanding AIO requests have been handled. + + Strictly equivalent to: + + IO::AIO::poll_wait, IO::AIO::poll_cb + while IO::AIO::nreqs; + IO::AIO::max_poll_reqs $nreqs IO::AIO::max_poll_time $seconds These set the maximum number of requests (default 0, meaning @@ -886,30 +1134,6 @@ poll => 'r', nice => 1, cb => &IO::AIO::poll_cb); - IO::AIO::poll_wait - If there are any outstanding requests and none of them in the result - phase, wait till the result filehandle becomes ready for reading - (simply does a "select" on the filehandle. This is useful if you - want to synchronously wait for some requests to finish). - - See "nreqs" for an example. - - IO::AIO::poll - Waits until some requests have been handled. - - Returns the number of requests processed, but is otherwise strictly - equivalent to: - - IO::AIO::poll_wait, IO::AIO::poll_cb - - IO::AIO::flush - Wait till all outstanding AIO requests have been handled. - - Strictly equivalent to: - - IO::AIO::poll_wait, IO::AIO::poll_cb - while IO::AIO::nreqs; - CONTROLLING THE NUMBER OF THREADS IO::AIO::min_parallel $nthreads Set the minimum number of AIO threads to $nthreads. The current @@ -948,9 +1172,10 @@ IO::AIO::max_idle $nthreads Limit the number of threads (default: 4) that are allowed to idle - (i.e., threads that did not get a request to process within 10 - seconds). That means if a thread becomes idle while $nthreads other - threads are also idle, it will free its resources and exit. + (i.e., threads that did not get a request to process within the idle + timeout (default: 10 seconds). That means if a thread becomes idle + while $nthreads other threads are also idle, it will free its + resources and exit. This is useful when you allow a large number of threads (e.g. 100 or 1000) to allow for extremely high load situations, but want to free @@ -961,23 +1186,44 @@ creation is fast. If thread creation is very slow on your system you might want to use larger values. + IO::AIO::idle_timeout $seconds + Sets the minimum idle timeout (default 10) after which worker + threads are allowed to exit. SEe "IO::AIO::max_idle". + IO::AIO::max_outstanding $maxreqs + Sets the maximum number of outstanding requests to $nreqs. If you do + queue up more than this number of requests, the next call to + "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as + "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is + no longer exceeded. + + In other words, this setting does not enforce a queue limit, but can + be used to make poll functions block if the limit is exceeded. + This is a very bad function to use in interactive programs because it blocks, and a bad way to reduce concurrency because it is inexact: Better use an "aio_group" together with a feed callback. - Sets the maximum number of outstanding requests to $nreqs. If you do - queue up more than this number of requests, the next call to the - "poll_cb" (and "poll_some" and other functions calling "poll_cb") - function will block until the limit is no longer exceeded. - - The default value is very large, so there is no practical limit on - the number of outstanding requests. - - You can still queue as many requests as you want. Therefore, - "max_outstanding" is mainly useful in simple scripts (with low - values) or as a stop gap to shield against fatal memory overflow - (with large values). + It's main use is in scripts without an event loop - when you want to + stat a lot of files, you can write somehting like this: + + IO::AIO::max_outstanding 32; + + for my $path (...) { + aio_stat $path , ...; + IO::AIO::poll_cb; + } + + IO::AIO::flush; + + The call to "poll_cb" inside the loop will normally return + instantly, but as soon as more thna 32 reqeusts are in-flight, it + will block until some requests have been handled. This keeps the + loop from pushing a large number of "aio_stat" requests onto the + queue. + + The default value for "max_outstanding" is very large, so there is + no practical limit on the number of outstanding requests. STATISTICAL INFORMATION IO::AIO::nreqs @@ -1011,7 +1257,7 @@ Returns the number of bytes copied, or -1 on error. IO::AIO::fadvise $fh, $offset, $len, $advice - Simply calls the "posix_fadvise" function (see it's manpage for + Simply calls the "posix_fadvise" function (see its manpage for details). The following advice constants are avaiable: "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL", "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE", @@ -1020,20 +1266,145 @@ On systems that do not implement "posix_fadvise", this function returns ENOSYS, otherwise the return value of "posix_fadvise". - FORK BEHAVIOUR - This module should do "the right thing" when the process using it forks: + IO::AIO::madvise $scalar, $offset, $len, $advice + Simply calls the "posix_madvise" function (see its manpage for + details). The following advice constants are avaiable: + "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL", + "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED", + "IO::AIO::MADV_DONTNEED". + + On systems that do not implement "posix_madvise", this function + returns ENOSYS, otherwise the return value of "posix_madvise". + + IO::AIO::mprotect $scalar, $offset, $len, $protect + Simply calls the "mprotect" function on the preferably AIO::mmap'ed + $scalar (see its manpage for details). The following protect + constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ", + "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC". + + On systems that do not implement "mprotect", this function returns + ENOSYS, otherwise the return value of "mprotect". + + IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset] + Memory-maps a file (or anonymous memory range) and attaches it to + the given $scalar, which will act like a string scalar. + + The only operations allowed on the scalar are "substr"/"vec" that + don't change the string length, and most read-only operations such + as copying it or searching it with regexes and so on. + + Anything else is unsafe and will, at best, result in memory leaks. + + The memory map associated with the $scalar is automatically removed + when the $scalar is destroyed, or when the "IO::AIO::mmap" or + "IO::AIO::munmap" functions are called. + + This calls the "mmap"(2) function internally. See your system's + manual page for details on the $length, $prot and $flags parameters. + + The $length must be larger than zero and smaller than the actual + filesize. + + $prot is a combination of "IO::AIO::PROT_NONE", + "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or + "IO::AIO::PROT_WRITE", + + $flags can be a combination of "IO::AIO::MAP_SHARED" or + "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when + not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS" + (which is set to "MAP_ANON" if your system only provides this + constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED", + "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or + "IO::AIO::MAP_NONBLOCK" + + If $fh is "undef", then a file descriptor of -1 is passed. + + $offset is the offset from the start of the file - it generally must + be a multiple of "IO::AIO::PAGESIZE" and defaults to 0. + + Example: - Before the fork, IO::AIO enters a quiescent state where no requests can - be added in other threads and no results will be processed. After the - fork the parent simply leaves the quiescent state and continues - request/result processing, while the child frees the request/result - queue (so that the requests started before the fork will only be handled - in the parent). Threads will be started on demand until the limit set in - the parent process has been reached again. - - In short: the parent will, after a short pause, continue as if fork had - not been called, while the child will act as if IO::AIO has not been - used yet. + use Digest::MD5; + use IO::AIO; + + open my $fh, "io (fd => IO::AIO::poll_fileno, + poll => 'r', + cb => \&IO::AIO::poll_cb); + + # Glib/Gtk2 integration + add_watch Glib::IO IO::AIO::poll_fileno, + in => sub { IO::AIO::poll_cb; 1 }; + + # Tk integration + Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", + readable => \&IO::AIO::poll_cb); + + # Danga::Socket integration + Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => + \&IO::AIO::poll_cb); + + FORK BEHAVIOUR + Usage of pthreads in a program changes the semantics of fork + considerably. Specifically, only async-safe functions can be called + after fork. Perl doesn't know about this, so in general, you cannot call + fork with defined behaviour in perl if pthreads are involved. IO::AIO + uses pthreads, so this applies, but many other extensions and (for + inexplicable reasons) perl itself often is linked against pthreads, so + this limitation applies to quite a lot of perls. + + This module no longer tries to fight your OS, or POSIX. That means + IO::AIO only works in the process that loaded it. Forking is fully + supported, but using IO::AIO in the child is not. + + You might get around by not *using* IO::AIO before (or after) forking. + You could also try to call the IO::AIO::reinit function in the child: + + IO::AIO::reinit + Abondons all current requests and I/O threads and simply + reinitialises all data structures. This is not an operation + suppported by any standards, but happens to work on GNU/Linux and + some newer BSD systems. + + The only reasonable use for this function is to call it after + forking, if "IO::AIO" was used in the parent. Calling it while + IO::AIO is active in the process will result in undefined behaviour. + Calling it at any time will also result in any undefined (by POSIX) + behaviour. MEMORY USAGE Per-request usage: