[ViewVC] Contents of: cvs/IO-AIO/Changes

Revision history for IO::AIO

TODO: better autoconf.pm that can return LIBS etc.
TODO: aio_cptree/mvtree
TODO: reduce condvar fairness: schedule hot-cache-threads first?
TODO: splice/tee/vmsplice/sync_file_range? (http://kerneltrap.org/node/6505 http://lwn.net/Articles/178199/)
TODO: aio_fcntl, at least for file-locking

3.02 Mon May 12 02:32:02 CEST 2008
        - fix a memory leak on aio_readlink.
        - bring back working fchmod.
        - nop and busy now set result to 0.
        - set errno to ENOMEM when allocation fails.

3.01 Sun May 11 03:07:03 CEST 2008
        - (libeio) make it compile on systems without readahead or readdir_r.
        - (libeio) improve configure check for readahead availability.
        - do not try to link against -lrt.
        - use a separate configure script for IO::AIO (not the libeio one).

3.0  Sun May 11 00:57:14 CEST 2008
        - added bin/treescan to the distribution.
        - switched to using libeio.
        - LOTS OF INCOMPATIBLE CHANGES:
          - remove signal functionality, it is not worth the effort.
          - max_outstanding no longer returns the previous number of requests.
          - poll_cb no longer returns number of requests.

2.62 Sat Apr 26 13:59:33 CEST 2008
        - port to solaris perls configured for old posix
          (analysed by Jost Krieger).
        - keep a reference to the perl filehandle object in aio_close,
          so it doesn't get closed prematurely, leading to ugly races.

2.61 Wed Apr 16 18:45:02 CEST 2008
        - fix treescan output duplication and improve output ordering.
          also display files given on the commandline.
        - use a different algorithm for aio_close that is faster
          and probably has even lower chances of blocking.
        - do our own stack memory management for threads - linux
          allocates outrageous amounts of VM (not so bad unless you
          use mlockall...), which severely limits the number of threads
          on 32-bit arches: stack size is the larger of PTHREAD_STACK_MIN
          and 4096 * sizeof (long) (usually this is 16..64k).

2.6  Sun Mar 30 08:28:11 CEST 2008
        - added aio_sync.
        - added aio_pathsync.
        - fix prototypes of (void) functions.

2.51 Sat Oct  6 16:04:54 CEST 2007
        - perlio isn't generally threadsafe, so aio_close could not work reliably.
          aio_close now tries a safe hack that might not be that asynchronous
          (see the manpage for details).
        - discard callback return values as to not grow the stack endlessly
          when poll_cb handles many requests without returning.
        - minor code cleanups.

2.5  Thu Oct  4 14:49:08 CEST 2007
        - replaced _fd2fh with faster xs code.
        - aio_close will now try to do "the right thing" and thus might
          work sensibly for the very first time.

2.41 Mon Sep 24 21:28:21 CEST 2007
        - after fork, invest some work to make sure that the poll_fileno
          stays stable (by dup2'ing the new fd over the old one), to make
          it easier for programs/libs that don't control their forking
          behaviour and cannot recreate their watchers.

2.4  Sun Aug  5 18:44:22 CEST 2007
        - add aio_truncate, aio_chmod, aio_chown, aio_utime (linux
          successfully demonstrated that you can block on futimes...).
        - allow undef as fileoffset for aio_read/write and use read/write(2)
          internally (useful for sockets or O_APPEND handles).
        - allow undef for length in aio_write.
        - negative dataoffsets work as expected now in aio_read/aio_write.
        - use NV instead of UV for 32 bit perls and file offsets, as NVs
          have a larger range then.
        - shared code between BDB and IO::AIO.
        - aio_busy was completely broken. now fixed.
        - readahead emulation now returns something.
        - correctly set errno to ENOSYS on unimplemented functions
          (should never happen, though).
        - large changes to make it partially compile and run on win32,
          but win32 lacks too much functionality, and perl overrides way
          too many functions with crashing versions.

2.33 Tue Jan 23 23:55:41 CET 2007
        - fix install path (Andreas J. Koenig).

2.32 Mon Jan 22 16:56:23 CET 2007
        - added aio_rmtree.
        - wow, aio_mkdir was missing.
        - aio_load did return undef on error, not -1.
        - use prefixexp not prefix in autoconf.pm
          (suggested by ... rt.cpan.org unreachable).
        - avoid installing autoconf.pm.

2.31 Sat Jan  6 03:46:02 CET 2007
        - added aio_load.

2.3  Sat Dec 23 05:48:07 CET 2006
        - fix off-by-one bug in aio_read, causing memory corruption
          or crashes.

2.21  Fri Dec 22 05:03:38 CET 2006
        - minor doc updates.
        - minor cleanups.
        - IO::AIO::poll returns request count.
        - undocumented and unfinished async-signal-reporting.

2.2  Tue Oct 31 00:31:00 CET 2006
        - minor doc updates.
        - added aio_readlink.
        - properly zero-terminate aio_read buffer.
        - fix aio_read/write with nonzero dataoffset.
        - reduced size of aio request structure.
        - better diagnostics when pathnames etc. are not byte-encoded;
          do not leak request in that case, either.

2.1  Sun Oct 29 02:01:57 CET 2006
        - INCOMPATIBLE CHANGE: replace IO::AIO::poll_some by
          IO::AIO::max_poll_reqs and IO::AIO::max_poll_time.
        - fix a bug in aio_move where it would fail everytime
          it would have to copy files manually.
        - doc updates.
        - start threads only on (very low) demand.
        - end superfluous threads automatically after 10s idling.
        - add IO::AIO::max_idle to control this.
        - some tuning applied to random places.
        - add aio_mknod.

2.0  Thu Oct 26 18:27:58 CEST 2006
        - minor incompatibility: max_outstanding semantics have changed.
        - major rewrite, consider all functionality EXPERIMENTAL.
        - aio requests can be cancelled.
        - callbacks can be (re-)set later.
        - aio requests can choose between 9 priorities.
        - add aio_group: aio requests can be grouped
          into composite requests.
        - generator interface for groups.
        - add IO::AIO::poll_some.
        - major documentation improvements.
        - very minor bugfixes.
        - add aio_nop for dummy requests.
        - add aio_busy mainly for benchmarking and debugging.
        - use "fast" mutexes on linux.
        - use dynamic (and larger) buffers instead of
          putting them onto the stack.
        - optimise x86 and amd64 a bit.
        - better error checking when ENOMEM.
        - hopefully fix mem and dirp leaks on fork.
        - warn about broken perl malloc.
        - compiles on cygwin (but pread is broken on cygwin
          which is not detected by autoconf, so you have to
          edit autoconf/config.h yourself to enable emulation).

1.8  Sat Jun 24 22:20:44 CEST 2006
        - add and/or document aio_rename, aio_link, aio_symlink and aio_move.

1.73 Wed Mar  1 22:49:32 CET 2006
        - codename "jost"
        - AIX/Solaris(?) aren't being helpful again, hardcode a value
          for NAME_MAX and drive with your eyes closed (reported by
          wcooley@nakedape.cc).

1.72 Thu Feb  2 00:40:44 CET 2006
        - another minor bug in aio_scandir, again, the callback was called
          twice when the directory can't be stat'ed.

1.71 Mon Dec 26 20:20:03 CET 2005
        - grr, another minor bug in aio_scandir, this time resulting
          in a runtime error.

1.7  Mon Dec 26 19:29:48 CET 2005
        - aio_scandir errornously called callback twice in some cases.
        - added AnyEvent example.

1.61 Wed Sep  7 19:40:42 CEST 2005
        - no longer include $Config{libs}, as distros include too much
          garbage in there that is not installed on typical systems
          (for example, debian links perl against -lgdbm and many more
          libraries despite perl not needing it, slowing down startup and
          wasting memory).

1.6  Tue Aug 30 17:44:44 CEST 2005
        - added aio_readdir, aio_scandir.
        - added aio_sendfile, including sendfile emulation when sendfile
          isn't available. Linux, FreeBSD and HP-UX might work (sendfilev
          support is unavailable on my solaris 8 machine, but preliminary
          code is there. What's lacking is configury stuff and testing...).

1.5  Sat Aug 20 02:32:19 CEST 2005
        - create the aio threads on demand only (good after forking).
        - somebody nagged about C89 compatibility, so this release should
          be C89 compatible, but no guarantees for future ones.
        - abort when the configure script fails.

1.4  Wed Aug 17 08:07:27 CEST 2005
        - forgot to recreate the pipe after forking, this could cause
          deadlocks.

1.3  Wed Aug 17 07:25:54 CEST 2005
        - properly propagate exceptions from callbacks, instead of silently
          eating them.
        - use a different fork algorithm that avoids recursive callback
          invocations and reduces fork latency in busy processes.
        - fix a bug where the buffer scalar in aio_read got assigned the wrong
          length after reading.
        - fix a bug where the child would process some outstanding requests
          from the parent.
        - make a copy of the callback scalar, to avoid some very uncommon
          (but valid) usages where the callback scalar changes.
        - the callback was never freed in aio_read/aio_write.
        - aio_read/aio_write will now set the readonly flag on the data
          scalar for better error reporting.

1.2  Wed Aug 17 01:22:58 CEST 2005
        - verified on cygwin, linux/amd64+ia32+alpha, solaris.
        - use SvPVbyte for filenames now. You *need* to encode your strings to
          the external filename encoding first.
        - fix the bug where filehandles could leak (again).
        - clarify freebsd situation: make it work and tell me how, or go away
          with your underdocumented, broken and outdated OS.
        - fork'ing should now be officially supported (where linux and
          posix contradict each other, I followed posix).
        - only call read() once per poll, not twice (speedup).
        - new functions: aio_rmdir, aio_symlink.
        - force callback arguments to be undef or a reference, for better
          error catching.

1.1  Sun Aug  7 05:27:23 CEST 2005
        - added configure script to detect availability of some calls.
          (imperfect, as we cannot detect things like -lrt due to missing
          feedback yet).
        - emulate fdatasync via fsync, pread/pwrite via unsafe read/write
          and readahead via manual reading on platforms lacking those.
        - ported t/03_errors.t+framework by Brad Fitzpatrick
          from Linux::AIO.
        - removed XOPEN_SOURCE because stupid solaris 9 doesn't
          compile with it enabled. Probably breaks others. Oh well.
        - try to be more careful with errno on non-threaded perls.
        - cygwins perl insisted on a matching open mode when morphing
          the fd to an fh.
        - convert sv's to "byte" encoding in aio_read/aio_write. Might
          do that for pathnames, too, in the future, so make sure you
          properly encode your pathnames.

1.0  Fri Jul 22 10:43:30 CEST 2005
        - aio_open did not reliably deliver (open) filehandles.
        - all aio_*-functions keep a reference to the filehandle so
          it doesn't go away while the aio requests is working on it.
        - disable warnings in AIO.pm.

0.9  Wed Jul 20 23:55:04 CEST 2005
        - allow recursive calls to poll_cb, use less locking calls, too.
        - fix the Gtk2-example in the SYNOPSIS.
        - use pread/pwrite not pread64/pwrite64. this was simply a leftover
          from Linux::AIO.
          (found by compiling on cygwin. Unfortunately, cygwin declares but
          does not implement pread/pwrite).
        - only include <sys/syscall.h> on linux.

0.5  Tue Jul 12 13:03:09 CEST 2005
        - removed #include <endian.h>, it's not portable, and we don't
          need it anyway.
        - link against -lrt, as it might contain goodies such as fdatasync,
          and often aio_read, which we do not use yet, but it shouldn't hurt.

0.4  Mon Jul 11 05:28:25 CEST 2005
        - added IO::AIO::flush, IO::AIO::poll.
        - make callback argument optional for all calls.

0.3  Mon Jul 11 01:42:37 CEST 2005
        - restructured manpage.
        - added SYNOPSIS with examples for Event, Glib, Tk.
        - remove explicit context support so I don't have to maintain
          it for threaded perls (i.e. it should work now :).

0.2  Sun Jul 10 22:57:12 CEST 2005
        - return immediately from poll_wait if nreqs==0.
        - get rid of the request pipe and use faster thread-thread
          communications for most requests and responses.

0.1
        - cloned from Linux::AIO, which is very similar.

Revision:	1.152
Committed:	Mon May 12 00:32:42 2008 UTC (16 years ago) by root
Branch:	MAIN
CVS Tags:	rel-3_02
Changes since 1.151:	+1 -0 lines
Log Message:	* empty log message *
#	Content
1	Revision history for IO::AIO
2
3	TODO: better autoconf.pm that can return LIBS etc.
4	TODO: aio_cptree/mvtree
5	TODO: reduce condvar fairness: schedule hot-cache-threads first?
6	TODO: splice/tee/vmsplice/sync_file_range? (http://kerneltrap.org/node/6505 http://lwn.net/Articles/178199/)
7	TODO: aio_fcntl, at least for file-locking
8
9	3.02 Mon May 12 02:32:02 CEST 2008
10	- fix a memory leak on aio_readlink.
11	- bring back working fchmod.
12	- nop and busy now set result to 0.
13	- set errno to ENOMEM when allocation fails.
14
15	3.01 Sun May 11 03:07:03 CEST 2008
16	- (libeio) make it compile on systems without readahead or readdir_r.
17	- (libeio) improve configure check for readahead availability.
18	- do not try to link against -lrt.
19	- use a separate configure script for IO::AIO (not the libeio one).
20
21	3.0 Sun May 11 00:57:14 CEST 2008
22	- added bin/treescan to the distribution.
23	- switched to using libeio.
24	- LOTS OF INCOMPATIBLE CHANGES:
25	- remove signal functionality, it is not worth the effort.
26	- max_outstanding no longer returns the previous number of requests.
27	- poll_cb no longer returns number of requests.
28
29	2.62 Sat Apr 26 13:59:33 CEST 2008
30	- port to solaris perls configured for old posix
31	(analysed by Jost Krieger).
32	- keep a reference to the perl filehandle object in aio_close,
33	so it doesn't get closed prematurely, leading to ugly races.
34
35	2.61 Wed Apr 16 18:45:02 CEST 2008
36	- fix treescan output duplication and improve output ordering.
37	also display files given on the commandline.
38	- use a different algorithm for aio_close that is faster
39	and probably has even lower chances of blocking.
40	- do our own stack memory management for threads - linux
41	allocates outrageous amounts of VM (not so bad unless you
42	use mlockall...), which severely limits the number of threads
43	on 32-bit arches: stack size is the larger of PTHREAD_STACK_MIN
44	and 4096 * sizeof (long) (usually this is 16..64k).
45
46	2.6 Sun Mar 30 08:28:11 CEST 2008
47	- added aio_sync.
48	- added aio_pathsync.
49	- fix prototypes of (void) functions.
50
51	2.51 Sat Oct 6 16:04:54 CEST 2007
52	- perlio isn't generally threadsafe, so aio_close could not work reliably.
53	aio_close now tries a safe hack that might not be that asynchronous
54	(see the manpage for details).
55	- discard callback return values as to not grow the stack endlessly
56	when poll_cb handles many requests without returning.
57	- minor code cleanups.
58
59	2.5 Thu Oct 4 14:49:08 CEST 2007
60	- replaced _fd2fh with faster xs code.
61	- aio_close will now try to do "the right thing" and thus might
62	work sensibly for the very first time.
63
64	2.41 Mon Sep 24 21:28:21 CEST 2007
65	- after fork, invest some work to make sure that the poll_fileno
66	stays stable (by dup2'ing the new fd over the old one), to make
67	it easier for programs/libs that don't control their forking
68	behaviour and cannot recreate their watchers.
69
70	2.4 Sun Aug 5 18:44:22 CEST 2007
71	- add aio_truncate, aio_chmod, aio_chown, aio_utime (linux
72	successfully demonstrated that you can block on futimes...).
73	- allow undef as fileoffset for aio_read/write and use read/write(2)
74	internally (useful for sockets or O_APPEND handles).
75	- allow undef for length in aio_write.
76	- negative dataoffsets work as expected now in aio_read/aio_write.
77	- use NV instead of UV for 32 bit perls and file offsets, as NVs
78	have a larger range then.
79	- shared code between BDB and IO::AIO.
80	- aio_busy was completely broken. now fixed.
81	- readahead emulation now returns something.
82	- correctly set errno to ENOSYS on unimplemented functions
83	(should never happen, though).
84	- large changes to make it partially compile and run on win32,
85	but win32 lacks too much functionality, and perl overrides way
86	too many functions with crashing versions.
87
88	2.33 Tue Jan 23 23:55:41 CET 2007
89	- fix install path (Andreas J. Koenig).
90
91	2.32 Mon Jan 22 16:56:23 CET 2007
92	- added aio_rmtree.
93	- wow, aio_mkdir was missing.
94	- aio_load did return undef on error, not -1.
95	- use prefixexp not prefix in autoconf.pm
96	(suggested by ... rt.cpan.org unreachable).
97	- avoid installing autoconf.pm.
98
99	2.31 Sat Jan 6 03:46:02 CET 2007
100	- added aio_load.
101
102	2.3 Sat Dec 23 05:48:07 CET 2006
103	- fix off-by-one bug in aio_read, causing memory corruption
104	or crashes.
105
106	2.21 Fri Dec 22 05:03:38 CET 2006
107	- minor doc updates.
108	- minor cleanups.
109	- IO::AIO::poll returns request count.
110	- undocumented and unfinished async-signal-reporting.
111
112	2.2 Tue Oct 31 00:31:00 CET 2006
113	- minor doc updates.
114	- added aio_readlink.
115	- properly zero-terminate aio_read buffer.
116	- fix aio_read/write with nonzero dataoffset.
117	- reduced size of aio request structure.
118	- better diagnostics when pathnames etc. are not byte-encoded;
119	do not leak request in that case, either.
120
121	2.1 Sun Oct 29 02:01:57 CET 2006
122	- INCOMPATIBLE CHANGE: replace IO::AIO::poll_some by
123	IO::AIO::max_poll_reqs and IO::AIO::max_poll_time.
124	- fix a bug in aio_move where it would fail everytime
125	it would have to copy files manually.
126	- doc updates.
127	- start threads only on (very low) demand.
128	- end superfluous threads automatically after 10s idling.
129	- add IO::AIO::max_idle to control this.
130	- some tuning applied to random places.
131	- add aio_mknod.
132
133	2.0 Thu Oct 26 18:27:58 CEST 2006
134	- minor incompatibility: max_outstanding semantics have changed.
135	- major rewrite, consider all functionality EXPERIMENTAL.
136	- aio requests can be cancelled.
137	- callbacks can be (re-)set later.
138	- aio requests can choose between 9 priorities.
139	- add aio_group: aio requests can be grouped
140	into composite requests.
141	- generator interface for groups.
142	- add IO::AIO::poll_some.
143	- major documentation improvements.
144	- very minor bugfixes.
145	- add aio_nop for dummy requests.
146	- add aio_busy mainly for benchmarking and debugging.
147	- use "fast" mutexes on linux.
148	- use dynamic (and larger) buffers instead of
149	putting them onto the stack.
150	- optimise x86 and amd64 a bit.
151	- better error checking when ENOMEM.
152	- hopefully fix mem and dirp leaks on fork.
153	- warn about broken perl malloc.
154	- compiles on cygwin (but pread is broken on cygwin
155	which is not detected by autoconf, so you have to
156	edit autoconf/config.h yourself to enable emulation).
157
158	1.8 Sat Jun 24 22:20:44 CEST 2006
159	- add and/or document aio_rename, aio_link, aio_symlink and aio_move.
160
161	1.73 Wed Mar 1 22:49:32 CET 2006
162	- codename "jost"
163	- AIX/Solaris(?) aren't being helpful again, hardcode a value
164	for NAME_MAX and drive with your eyes closed (reported by
165	wcooley@nakedape.cc).
166
167	1.72 Thu Feb 2 00:40:44 CET 2006
168	- another minor bug in aio_scandir, again, the callback was called
169	twice when the directory can't be stat'ed.
170
171	1.71 Mon Dec 26 20:20:03 CET 2005
172	- grr, another minor bug in aio_scandir, this time resulting
173	in a runtime error.
174
175	1.7 Mon Dec 26 19:29:48 CET 2005
176	- aio_scandir errornously called callback twice in some cases.
177	- added AnyEvent example.
178
179	1.61 Wed Sep 7 19:40:42 CEST 2005
180	- no longer include $Config{libs}, as distros include too much
181	garbage in there that is not installed on typical systems
182	(for example, debian links perl against -lgdbm and many more
183	libraries despite perl not needing it, slowing down startup and
184	wasting memory).
185
186	1.6 Tue Aug 30 17:44:44 CEST 2005
187	- added aio_readdir, aio_scandir.
188	- added aio_sendfile, including sendfile emulation when sendfile
189	isn't available. Linux, FreeBSD and HP-UX might work (sendfilev
190	support is unavailable on my solaris 8 machine, but preliminary
191	code is there. What's lacking is configury stuff and testing...).
192
193	1.5 Sat Aug 20 02:32:19 CEST 2005
194	- create the aio threads on demand only (good after forking).
195	- somebody nagged about C89 compatibility, so this release should
196	be C89 compatible, but no guarantees for future ones.
197	- abort when the configure script fails.
198
199	1.4 Wed Aug 17 08:07:27 CEST 2005
200	- forgot to recreate the pipe after forking, this could cause
201	deadlocks.
202
203	1.3 Wed Aug 17 07:25:54 CEST 2005
204	- properly propagate exceptions from callbacks, instead of silently
205	eating them.
206	- use a different fork algorithm that avoids recursive callback
207	invocations and reduces fork latency in busy processes.
208	- fix a bug where the buffer scalar in aio_read got assigned the wrong
209	length after reading.
210	- fix a bug where the child would process some outstanding requests
211	from the parent.
212	- make a copy of the callback scalar, to avoid some very uncommon
213	(but valid) usages where the callback scalar changes.
214	- the callback was never freed in aio_read/aio_write.
215	- aio_read/aio_write will now set the readonly flag on the data
216	scalar for better error reporting.
217
218	1.2 Wed Aug 17 01:22:58 CEST 2005
219	- verified on cygwin, linux/amd64+ia32+alpha, solaris.
220	- use SvPVbyte for filenames now. You need to encode your strings to
221	the external filename encoding first.
222	- fix the bug where filehandles could leak (again).
223	- clarify freebsd situation: make it work and tell me how, or go away
224	with your underdocumented, broken and outdated OS.
225	- fork'ing should now be officially supported (where linux and
226	posix contradict each other, I followed posix).
227	- only call read() once per poll, not twice (speedup).
228	- new functions: aio_rmdir, aio_symlink.
229	- force callback arguments to be undef or a reference, for better
230	error catching.
231
232	1.1 Sun Aug 7 05:27:23 CEST 2005
233	- added configure script to detect availability of some calls.
234	(imperfect, as we cannot detect things like -lrt due to missing
235	feedback yet).
236	- emulate fdatasync via fsync, pread/pwrite via unsafe read/write
237	and readahead via manual reading on platforms lacking those.
238	- ported t/03_errors.t+framework by Brad Fitzpatrick
239	from Linux::AIO.
240	- removed XOPEN_SOURCE because stupid solaris 9 doesn't
241	compile with it enabled. Probably breaks others. Oh well.
242	- try to be more careful with errno on non-threaded perls.
243	- cygwins perl insisted on a matching open mode when morphing
244	the fd to an fh.
245	- convert sv's to "byte" encoding in aio_read/aio_write. Might
246	do that for pathnames, too, in the future, so make sure you
247	properly encode your pathnames.
248
249	1.0 Fri Jul 22 10:43:30 CEST 2005
250	- aio_open did not reliably deliver (open) filehandles.
251	- all aio_*-functions keep a reference to the filehandle so
252	it doesn't go away while the aio requests is working on it.
253	- disable warnings in AIO.pm.
254
255	0.9 Wed Jul 20 23:55:04 CEST 2005
256	- allow recursive calls to poll_cb, use less locking calls, too.
257	- fix the Gtk2-example in the SYNOPSIS.
258	- use pread/pwrite not pread64/pwrite64. this was simply a leftover
259	from Linux::AIO.
260	(found by compiling on cygwin. Unfortunately, cygwin declares but
261	does not implement pread/pwrite).
262	- only include <sys/syscall.h> on linux.
263
264	0.5 Tue Jul 12 13:03:09 CEST 2005
265	- removed #include <endian.h>, it's not portable, and we don't
266	need it anyway.
267	- link against -lrt, as it might contain goodies such as fdatasync,
268	and often aio_read, which we do not use yet, but it shouldn't hurt.
269
270	0.4 Mon Jul 11 05:28:25 CEST 2005
271	- added IO::AIO::flush, IO::AIO::poll.
272	- make callback argument optional for all calls.
273
274	0.3 Mon Jul 11 01:42:37 CEST 2005
275	- restructured manpage.
276	- added SYNOPSIS with examples for Event, Glib, Tk.
277	- remove explicit context support so I don't have to maintain
278	it for threaded perls (i.e. it should work now :).
279
280	0.2 Sun Jul 10 22:57:12 CEST 2005
281	- return immediately from poll_wait if nreqs==0.
282	- get rid of the request pipe and use faster thread-thread
283	communications for most requests and responses.
284
285	0.1
286	- cloned from Linux::AIO, which is very similar.
287