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178 | you actually want to know. Also interesting is the combination of |
178 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_update_now> and C<ev_now>. |
180 | |
180 | |
181 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
182 | |
182 | |
183 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
184 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
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185 | passed (approximately - it might return a bit earlier even if not |
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186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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187 | |
185 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
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189 | |
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190 | The range of the C<interval> is limited - libev only guarantees to work |
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191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
186 | |
192 | |
187 | =item int ev_version_major () |
193 | =item int ev_version_major () |
188 | |
194 | |
189 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
190 | |
196 | |
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499 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
500 | forks then I<both> parent and child process have to recreate the epoll |
506 | forks then I<both> parent and child process have to recreate the epoll |
501 | set, which can take considerable time (one syscall per file descriptor) |
507 | set, which can take considerable time (one syscall per file descriptor) |
502 | and is of course hard to detect. |
508 | and is of course hard to detect. |
503 | |
509 | |
504 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
505 | of course I<doesn't>, and epoll just loves to report events for totally |
511 | but of course I<doesn't>, and epoll just loves to report events for |
506 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
507 | even remove them from the set) than registered in the set (especially |
513 | one cannot even remove them from the set) than registered in the set |
508 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
509 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
510 | events to filter out spurious ones, recreating the set when required. Last |
516 | that against the events to filter out spurious ones, recreating the set |
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517 | when required. Epoll also errornously rounds down timeouts, but gives you |
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518 | no way to know when and by how much, so sometimes you have to busy-wait |
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519 | because epoll returns immediately despite a nonzero timeout. And last |
511 | not least, it also refuses to work with some file descriptors which work |
520 | not least, it also refuses to work with some file descriptors which work |
512 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
513 | |
522 | |
514 | Epoll is truly the train wreck analog among event poll mechanisms, |
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
515 | a frankenpoll, cobbled together in a hurry, no thought to design or |
524 | cobbled together in a hurry, no thought to design or interaction with |
516 | interaction with others. |
525 | others. Oh, the pain, will it ever stop... |
517 | |
526 | |
518 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
519 | will result in some caching, there is still a system call per such |
528 | will result in some caching, there is still a system call per such |
520 | incident (because the same I<file descriptor> could point to a different |
529 | incident (because the same I<file descriptor> could point to a different |
521 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
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825 | This is useful if you are waiting for some external event in conjunction |
834 | This is useful if you are waiting for some external event in conjunction |
826 | with something not expressible using other libev watchers (i.e. "roll your |
835 | with something not expressible using other libev watchers (i.e. "roll your |
827 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
836 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
828 | usually a better approach for this kind of thing. |
837 | usually a better approach for this kind of thing. |
829 | |
838 | |
830 | Here are the gory details of what C<ev_run> does: |
839 | Here are the gory details of what C<ev_run> does (this is for your |
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840 | understanding, not a guarantee that things will work exactly like this in |
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841 | future versions): |
831 | |
842 | |
832 | - Increment loop depth. |
843 | - Increment loop depth. |
833 | - Reset the ev_break status. |
844 | - Reset the ev_break status. |
834 | - Before the first iteration, call any pending watchers. |
845 | - Before the first iteration, call any pending watchers. |
835 | LOOP: |
846 | LOOP: |