ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/libev/ev.pod
(Generate patch)

Comparing libev/ev.pod (file contents):
Revision 1.239 by root, Tue Apr 21 14:14:19 2009 UTC vs.
Revision 1.241 by root, Sat Apr 25 14:23:26 2009 UTC

… …
1465year, it will still time out after (roughly) one hour. "Roughly" because 1465year, it will still time out after (roughly) one hour. "Roughly" because
1466detecting time jumps is hard, and some inaccuracies are unavoidable (the 1466detecting time jumps is hard, and some inaccuracies are unavoidable (the
1467monotonic clock option helps a lot here). 1467monotonic clock option helps a lot here).
1468 1468
1469The callback is guaranteed to be invoked only I<after> its timeout has 1469The callback is guaranteed to be invoked only I<after> its timeout has
1470passed. If multiple timers become ready during the same loop iteration 1470passed (not I<at>, so on systems with very low-resolution clocks this
1471then the ones with earlier time-out values are invoked before ones with 1471might introduce a small delay). If multiple timers become ready during the
1472same loop iteration then the ones with earlier time-out values are invoked
1472later time-out values (but this is no longer true when a callback calls 1473before ones with later time-out values (but this is no longer true when a
1473C<ev_loop> recursively). 1474callback calls C<ev_loop> recursively).
1474 1475
1475=head3 Be smart about timeouts 1476=head3 Be smart about timeouts
1476 1477
1477Many real-world problems involve some kind of timeout, usually for error 1478Many real-world problems involve some kind of timeout, usually for error
1478recovery. A typical example is an HTTP request - if the other side hangs, 1479recovery. A typical example is an HTTP request - if the other side hangs,
… …
3934way (note also that glib is the slowest event library known to man). 3935way (note also that glib is the slowest event library known to man).
3935 3936
3936There is no supported compilation method available on windows except 3937There is no supported compilation method available on windows except
3937embedding it into other applications. 3938embedding it into other applications.
3938 3939
3940Sensible signal handling is officially unsupported by Microsoft - libev
3941tries its best, but under most conditions, signals will simply not work.
3942
3939Not a libev limitation but worth mentioning: windows apparently doesn't 3943Not a libev limitation but worth mentioning: windows apparently doesn't
3940accept large writes: instead of resulting in a partial write, windows will 3944accept large writes: instead of resulting in a partial write, windows will
3941either accept everything or return C<ENOBUFS> if the buffer is too large, 3945either accept everything or return C<ENOBUFS> if the buffer is too large,
3942so make sure you only write small amounts into your sockets (less than a 3946so make sure you only write small amounts into your sockets (less than a
3943megabyte seems safe, but this apparently depends on the amount of memory 3947megabyte seems safe, but this apparently depends on the amount of memory
… …
3947the abysmal performance of winsockets, using a large number of sockets 3951the abysmal performance of winsockets, using a large number of sockets
3948is not recommended (and not reasonable). If your program needs to use 3952is not recommended (and not reasonable). If your program needs to use
3949more than a hundred or so sockets, then likely it needs to use a totally 3953more than a hundred or so sockets, then likely it needs to use a totally
3950different implementation for windows, as libev offers the POSIX readiness 3954different implementation for windows, as libev offers the POSIX readiness
3951notification model, which cannot be implemented efficiently on windows 3955notification model, which cannot be implemented efficiently on windows
3952(Microsoft monopoly games). 3956(due to Microsoft monopoly games).
3953 3957
3954A typical way to use libev under windows is to embed it (see the embedding 3958A typical way to use libev under windows is to embed it (see the embedding
3955section for details) and use the following F<evwrap.h> header file instead 3959section for details) and use the following F<evwrap.h> header file instead
3956of F<ev.h>: 3960of F<ev.h>:
3957 3961
… …
3993 3997
3994Early versions of winsocket's select only supported waiting for a maximum 3998Early versions of winsocket's select only supported waiting for a maximum
3995of C<64> handles (probably owning to the fact that all windows kernels 3999of C<64> handles (probably owning to the fact that all windows kernels
3996can only wait for C<64> things at the same time internally; Microsoft 4000can only wait for C<64> things at the same time internally; Microsoft
3997recommends spawning a chain of threads and wait for 63 handles and the 4001recommends spawning a chain of threads and wait for 63 handles and the
3998previous thread in each. Great). 4002previous thread in each. Sounds great!).
3999 4003
4000Newer versions support more handles, but you need to define C<FD_SETSIZE> 4004Newer versions support more handles, but you need to define C<FD_SETSIZE>
4001to some high number (e.g. C<2048>) before compiling the winsocket select 4005to some high number (e.g. C<2048>) before compiling the winsocket select
4002call (which might be in libev or elsewhere, for example, perl does its own 4006call (which might be in libev or elsewhere, for example, perl and many
4003select emulation on windows). 4007other interpreters do their own select emulation on windows).
4004 4008
4005Another limit is the number of file descriptors in the Microsoft runtime 4009Another limit is the number of file descriptors in the Microsoft runtime
4006libraries, which by default is C<64> (there must be a hidden I<64> fetish 4010libraries, which by default is C<64> (there must be a hidden I<64>
4007or something like this inside Microsoft). You can increase this by calling 4011fetish or something like this inside Microsoft). You can increase this
4008C<_setmaxstdio>, which can increase this limit to C<2048> (another 4012by calling C<_setmaxstdio>, which can increase this limit to C<2048>
4009arbitrary limit), but is broken in many versions of the Microsoft runtime 4013(another arbitrary limit), but is broken in many versions of the Microsoft
4010libraries.
4011
4012This might get you to about C<512> or C<2048> sockets (depending on 4014runtime libraries. This might get you to about C<512> or C<2048> sockets
4013windows version and/or the phase of the moon). To get more, you need to 4015(depending on windows version and/or the phase of the moon). To get more,
4014wrap all I/O functions and provide your own fd management, but the cost of 4016you need to wrap all I/O functions and provide your own fd management, but
4015calling select (O(n²)) will likely make this unworkable. 4017the cost of calling select (O(n²)) will likely make this unworkable.
4016 4018
4017=back 4019=back
4018 4020
4019=head2 PORTABILITY REQUIREMENTS 4021=head2 PORTABILITY REQUIREMENTS
4020 4022

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines