X-Git-Url: https://git.llucax.com/software/libev.git/blobdiff_plain/db2ba1d67df543c8e0dbfc578005b065983bdc94..7a5cc2e0a749c9e9f9b2aaa2018f75eaaf46958c:/ev.pod diff --git a/ev.pod b/ev.pod index d1d8348..9ef6da2 100644 --- a/ev.pod +++ b/ev.pod @@ -6,7 +6,7 @@ libev - a high performance full-featured event loop written in C #include -=head1 EXAMPLE PROGRAM +=head2 EXAMPLE PROGRAM #include @@ -67,7 +67,7 @@ watchers>, which are relatively small C structures you initialise with the details of the event, and then hand it over to libev by I the watcher. -=head1 FEATURES +=head2 FEATURES Libev supports C function doesn't follow POSIX in that it requires +socket I and not socket I. This makes select +very inefficient, and also requires a mapping from file descriptors +to socket handles. See the discussion of the C, +C and C preprocessor +symbols for more info. + +The configuration for a "naked" win32 using the microsoft runtime +libraries and raw winsocket select is: + + #define EV_USE_SELECT 1 + #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ + +Note that winsockets handling of fd sets is O(n), so you can easily get a +complexity in the O(n²) range when using win32. + +=item Limited number of file descriptors + +Windows has numerous arbitrary (and low) limits on things. Early versions +of winsocket's select only supported waiting for a max. of C<64> handles +(probably owning to the fact that all windows kernels can only wait for +C<64> things at the same time internally; microsoft recommends spawning a +chain of threads and wait for 63 handles and the previous thread in each). + +Newer versions support more handles, but you need to define C +to some high number (e.g. C<2048>) before compiling the winsocket select +call (which might be in libev or elsewhere, for example, perl does its own +select emulation on windows). + +Another limit is the number of file descriptors in the microsoft runtime +libraries, which by default is C<64> (there must be a hidden I<64> fetish +or something like this inside microsoft). You can increase this by calling +C<_setmaxstdio>, which can increase this limit to C<2048> (another +arbitrary limit), but is broken in many versions of the microsoft runtime +libraries. + +This might get you to about C<512> or C<2048> sockets (depending on +windows version and/or the phase of the moon). To get more, you need to +wrap all I/O functions and provide your own fd management, but the cost of +calling select (O(n²)) will likely make this unworkable. =back