| created | 2021-11-15T01:05:44Z |
|---|---|
| begin | 2021-11-12T00:00:00Z |
| end | 2021-11-12T04:34:23Z |
| path | src/sys |
| commits | 2 |
| date | 2021-11-12T04:34:22Z | |||
|---|---|---|---|---|
| author | visa | |||
| files | src/sys/kern/kern_event.c | log | diff | annotate |
| src/sys/kern/sys_generic.c | log | diff | annotate | |
| message |
Keep knotes between poll/select systems calls Reduce the time overhead of kqueue-based poll(2) and select(2) by keeping knotes registered between the system calls. It is expected that the set of monitored file descriptors is relatively unchanged between consecutive iterations of these system calls. By keeping the knotes, the system saves the effort of repeated knote unregistering and re-registering. To avoid receiving events from file descriptors that are no longer in the monitored set, each poll/select knote is assigned an increasing serial number. Every iteration of poll/select uses a previously unused range of serials for its knotes. In the setup stage, kqueue_register() updates the serials of any existing knotes in the currently monitored set. Function kqueue_scan() delivers only the events whose serials are recent enough; expired knotes are dropped. When the serial range is about to wrap around, all the knotes in the kqueue backend are dropped. This change is a space-time tradeoff. Memory usage is increased somewhat because of the retained knotes. The increase is limited by the number of open file descriptors and active threads. Idea from DragonFly BSD, initial patch by mpi@, kqueue_scan()-based approach by me. Tested by anton@ and mpi@ OK mpi@ |
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| date | 2021-11-12T04:34:23Z | |||
|---|---|---|---|---|
| author | visa | |||
| files | src/sys/sys/event.h | log | diff | annotate |
| message |
Keep knotes between poll/select systems calls Reduce the time overhead of kqueue-based poll(2) and select(2) by keeping knotes registered between the system calls. It is expected that the set of monitored file descriptors is relatively unchanged between consecutive iterations of these system calls. By keeping the knotes, the system saves the effort of repeated knote unregistering and re-registering. To avoid receiving events from file descriptors that are no longer in the monitored set, each poll/select knote is assigned an increasing serial number. Every iteration of poll/select uses a previously unused range of serials for its knotes. In the setup stage, kqueue_register() updates the serials of any existing knotes in the currently monitored set. Function kqueue_scan() delivers only the events whose serials are recent enough; expired knotes are dropped. When the serial range is about to wrap around, all the knotes in the kqueue backend are dropped. This change is a space-time tradeoff. Memory usage is increased somewhat because of the retained knotes. The increase is limited by the number of open file descriptors and active threads. Idea from DragonFly BSD, initial patch by mpi@, kqueue_scan()-based approach by me. Tested by anton@ and mpi@ OK mpi@ |
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