| … | |
… | |
| 483 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
483 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
| 484 | |
484 | |
| 485 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
485 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
| 486 | kernels). |
486 | kernels). |
| 487 | |
487 | |
| 488 | For few fds, this backend is a bit little slower than poll and select, |
488 | For few fds, this backend is a bit little slower than poll and select, but |
| 489 | but it scales phenomenally better. While poll and select usually scale |
489 | it scales phenomenally better. While poll and select usually scale like |
| 490 | like O(total_fds) where n is the total number of fds (or the highest fd), |
490 | O(total_fds) where total_fds is the total number of fds (or the highest |
| 491 | epoll scales either O(1) or O(active_fds). |
491 | fd), epoll scales either O(1) or O(active_fds). |
| 492 | |
492 | |
| 493 | The epoll mechanism deserves honorable mention as the most misdesigned |
493 | The epoll mechanism deserves honorable mention as the most misdesigned |
| 494 | of the more advanced event mechanisms: mere annoyances include silently |
494 | of the more advanced event mechanisms: mere annoyances include silently |
| 495 | dropping file descriptors, requiring a system call per change per file |
495 | dropping file descriptors, requiring a system call per change per file |
| 496 | descriptor (and unnecessary guessing of parameters), problems with dup, |
496 | descriptor (and unnecessary guessing of parameters), problems with dup, |
| … | |
… | |
| 825 | This is useful if you are waiting for some external event in conjunction |
825 | 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 |
826 | 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 |
827 | 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. |
828 | usually a better approach for this kind of thing. |
| 829 | |
829 | |
| 830 | Here are the gory details of what C<ev_run> does: |
830 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
831 | understanding, not a guarantee that things will work exactly like this in |
|
|
832 | future versions): |
| 831 | |
833 | |
| 832 | - Increment loop depth. |
834 | - Increment loop depth. |
| 833 | - Reset the ev_break status. |
835 | - Reset the ev_break status. |
| 834 | - Before the first iteration, call any pending watchers. |
836 | - Before the first iteration, call any pending watchers. |
| 835 | LOOP: |
837 | LOOP: |
