diff options
| author | root <root> | 2011-06-02 23:42:40 +0000 |
|---|---|---|
| committer | root <root> | 2011-06-02 23:42:40 +0000 |
| commit | 2e973617d5c21aa162c0a3852efdfe2812c24e53 (patch) | |
| tree | a0d8bca29be9552d6ea9938d84106370ce85ff2b | |
| parent | b31cc1b7e254fb3aea85cd551aec6feb39cb3eef (diff) | |
*** empty log message ***
| -rw-r--r-- | ev.pod | 23 |
1 files changed, 13 insertions, 10 deletions
@@ -501,19 +501,22 @@ forks then I<both> parent and child process have to recreate the epoll set, which can take considerable time (one syscall per file descriptor) and is of course hard to detect. -Epoll is also notoriously buggy - embedding epoll fds I<should> work, but -of course I<doesn't>, and epoll just loves to report events for totally -I<different> file descriptors (even already closed ones, so one cannot -even remove them from the set) than registered in the set (especially -on SMP systems). Libev tries to counter these spurious notifications by -employing an additional generation counter and comparing that against the -events to filter out spurious ones, recreating the set when required. Last +Epoll is also notoriously buggy - embedding epoll fds I<should> work, +but of course I<doesn't>, and epoll just loves to report events for +totally I<different> file descriptors (even already closed ones, so +one cannot even remove them from the set) than registered in the set +(especially on SMP systems). Libev tries to counter these spurious +notifications by employing an additional generation counter and comparing +that against the events to filter out spurious ones, recreating the set +when required. Epoll also errornously rounds down timeouts, but gives you +no way to know when and by how much, so sometimes you have to busy-wait +because epoll returns immediately despite a nonzero timeout. And last not least, it also refuses to work with some file descriptors which work perfectly fine with C<select> (files, many character devices...). -Epoll is truly the train wreck analog among event poll mechanisms, -a frankenpoll, cobbled together in a hurry, no thought to design or -interaction with others. +Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, +cobbled together in a hurry, no thought to design or interaction with +others. Oh, the pain, will it ever stop... While stopping, setting and starting an I/O watcher in the same iteration will result in some caching, there is still a system call per such |