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Comparing libev/ev.pod (file contents):
Revision 1.111 by root, Tue Dec 25 18:01:20 2007 UTC vs.
Revision 1.113 by root, Mon Dec 31 01:30:53 2007 UTC

… …
551usually a better approach for this kind of thing. 551usually a better approach for this kind of thing.
552 552
553Here are the gory details of what C<ev_loop> does: 553Here are the gory details of what C<ev_loop> does:
554 554
555 - Before the first iteration, call any pending watchers. 555 - Before the first iteration, call any pending watchers.
556 * If there are no active watchers (reference count is zero), return. 556 * If EVFLAG_FORKCHECK was used, check for a fork.
557 - Queue all prepare watchers and then call all outstanding watchers. 557 - If a fork was detected, queue and call all fork watchers.
558 - Queue and call all prepare watchers.
558 - If we have been forked, recreate the kernel state. 559 - If we have been forked, recreate the kernel state.
559 - Update the kernel state with all outstanding changes. 560 - Update the kernel state with all outstanding changes.
560 - Update the "event loop time". 561 - Update the "event loop time".
561 - Calculate for how long to block. 562 - Calculate for how long to sleep or block, if at all
563 (active idle watchers, EVLOOP_NONBLOCK or not having
564 any active watchers at all will result in not sleeping).
565 - Sleep if the I/O and timer collect interval say so.
562 - Block the process, waiting for any events. 566 - Block the process, waiting for any events.
563 - Queue all outstanding I/O (fd) events. 567 - Queue all outstanding I/O (fd) events.
564 - Update the "event loop time" and do time jump handling. 568 - Update the "event loop time" and do time jump handling.
565 - Queue all outstanding timers. 569 - Queue all outstanding timers.
566 - Queue all outstanding periodics. 570 - Queue all outstanding periodics.
567 - If no events are pending now, queue all idle watchers. 571 - If no events are pending now, queue all idle watchers.
568 - Queue all check watchers. 572 - Queue all check watchers.
569 - Call all queued watchers in reverse order (i.e. check watchers first). 573 - Call all queued watchers in reverse order (i.e. check watchers first).
570 Signals and child watchers are implemented as I/O watchers, and will 574 Signals and child watchers are implemented as I/O watchers, and will
571 be handled here by queueing them when their watcher gets executed. 575 be handled here by queueing them when their watcher gets executed.
572 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 576 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573 were used, return, otherwise continue with step *. 577 were used, or there are no active watchers, return, otherwise
578 continue with step *.
574 579
575Example: Queue some jobs and then loop until no events are outsanding 580Example: Queue some jobs and then loop until no events are outsanding
576anymore. 581anymore.
577 582
578 ... queue jobs here, make sure they register event watchers as long 583 ... queue jobs here, make sure they register event watchers as long
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2491be used is the winsock select). This means that it will call 2496be used is the winsock select). This means that it will call
2492C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2497C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2493it is assumed that all these functions actually work on fds, even 2498it is assumed that all these functions actually work on fds, even
2494on win32. Should not be defined on non-win32 platforms. 2499on win32. Should not be defined on non-win32 platforms.
2495 2500
2501=item EV_FD_TO_WIN32_HANDLE
2502
2503If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2504file descriptors to socket handles. When not defining this symbol (the
2505default), then libev will call C<_get_osfhandle>, which is usually
2506correct. In some cases, programs use their own file descriptor management,
2507in which case they can provide this function to map fds to socket handles.
2508
2496=item EV_USE_POLL 2509=item EV_USE_POLL
2497 2510
2498If defined to be C<1>, libev will compile in support for the C<poll>(2) 2511If defined to be C<1>, libev will compile in support for the C<poll>(2)
2499backend. Otherwise it will be enabled on non-win32 platforms. It 2512backend. Otherwise it will be enabled on non-win32 platforms. It
2500takes precedence over select. 2513takes precedence over select.
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2772watchers becomes O(1) w.r.t. prioritiy handling. 2785watchers becomes O(1) w.r.t. prioritiy handling.
2773 2786
2774=back 2787=back
2775 2788
2776 2789
2790=head1 Win32 platform limitations and workarounds
2791
2792Win32 doesn't support any of the standards (e.g. POSIX) that libev
2793requires, and its I/O model is fundamentally incompatible with the POSIX
2794model. Libev still offers limited functionality on this platform in
2795the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2796descriptors. This only applies when using Win32 natively, not when using
2797e.g. cygwin.
2798
2799There is no supported compilation method available on windows except
2800embedding it into other applications.
2801
2802Due to the many, low, and arbitrary limits on the win32 platform and the
2803abysmal performance of winsockets, using a large number of sockets is not
2804recommended (and not reasonable). If your program needs to use more than
2805a hundred or so sockets, then likely it needs to use a totally different
2806implementation for windows, as libev offers the POSIX model, which cannot
2807be implemented efficiently on windows (microsoft monopoly games).
2808
2809=over 4
2810
2811=item The winsocket select function
2812
2813The winsocket C<select> function doesn't follow POSIX in that it requires
2814socket I<handles> and not socket I<file descriptors>. This makes select
2815very inefficient, and also requires a mapping from file descriptors
2816to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2817C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2818symbols for more info.
2819
2820The configuration for a "naked" win32 using the microsoft runtime
2821libraries and raw winsocket select is:
2822
2823 #define EV_USE_SELECT 1
2824 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2825
2826Note that winsockets handling of fd sets is O(n), so you can easily get a
2827complexity in the O(n²) range when using win32.
2828
2829=item Limited number of file descriptors
2830
2831Windows has numerous arbitrary (and low) limits on things. Early versions
2832of winsocket's select only supported waiting for a max. of C<64> handles
2833(probably owning to the fact that all windows kernels can only wait for
2834C<64> things at the same time internally; microsoft recommends spawning a
2835chain of threads and wait for 63 handles and the previous thread in each).
2836
2837Newer versions support more handles, but you need to define C<FD_SETSIZE>
2838to some high number (e.g. C<2048>) before compiling the winsocket select
2839call (which might be in libev or elsewhere, for example, perl does its own
2840select emulation on windows).
2841
2842Another limit is the number of file descriptors in the microsoft runtime
2843libraries, which by default is C<64> (there must be a hidden I<64> fetish
2844or something like this inside microsoft). You can increase this by calling
2845C<_setmaxstdio>, which can increase this limit to C<2048> (another
2846arbitrary limit), but is broken in many versions of the microsoft runtime
2847libraries.
2848
2849This might get you to about C<512> or C<2048> sockets (depending on
2850windows version and/or the phase of the moon). To get more, you need to
2851wrap all I/O functions and provide your own fd management, but the cost of
2852calling select (O(n²)) will likely make this unworkable.
2853
2854=back
2855
2856
2777=head1 AUTHOR 2857=head1 AUTHOR
2778 2858
2779Marc Lehmann <libev@schmorp.de>. 2859Marc Lehmann <libev@schmorp.de>.
2780 2860

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