From: Eliezer T. <eli...@li...> - 2013-06-24 07:28:12
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David, Here is a rework of the select/poll patch. When select or poll are used on a lot of sockets the sysctl value needs to be set higher than 50. For 300 sockets a setting of 100 works for me. For 1000 sockets a setting of 200 works well but the gain is very small, probably not worth it. I should mention that unlike the version we had in v9, with this version of the patch, LLS always performs better than no LLS. In this version I split the sysctl entries into two. sysctl.net.core.low_latency_read for blocking socket reads. sysctl.net.core.low_latency_poll for select/poll. The main reason we need two sysctl entries is that the values are different. This also allows poll to busy poll only on some sockets. You set sysctl.net.core.low_latency_poll, but leave the read value 0. Then you use the socket option to enable SO_LL only on the sockets you would like to buys poll on. Maybe what we really want is a cgroup that would allow settings per-process group. -Eliezer Change log: v4 - cleaned up formatting v3 - split sysctl value into two separate ones, one for read and one for poll. - updated Documentation/sysctl/net.txt - fixed possible overflow (again) reported by Eric Dumazet. - poll/select loop optimizations by Eric Dumazet and Willem de Bruijn. v2 - added POLL_LL flag, used to signal between the syscalls and sock_poll(). - add a separate ll_end_time() function to be used from poll. - slight reorder of sk_poll_ll so the timing primitives are not used when called from sock_poll(). - select/poll stop busy polling as soon as there is something to return to the user. Change log from the original LLS patch series: v9 - better mask testing in sock_poll(), reported by Eric Dumazet. v8 - split out udp and select/poll into separate patches. what used to be patch 2/5 is now three patches. v5 - added simple poll/select support |