Ping Eric! Would you have a chance to review the proposed text below, please. Thanks, Michael On 02/19/2017 09:55 PM, Michael Kerrisk (man-pages) wrote: > [CC += Eric, so that he might review] > > Hello Francois, > > On 02/18/2017 05:06 AM, Francois Saint-Jacques wrote: >> This socket option is undocumented. Applies on the latest version >> (man-pages-4.09-511). >> >> diff --git a/man7/socket.7 b/man7/socket.7 >> index 3efd7a5d8..1a3ffa253 100644 >> --- a/man7/socket.7 >> +++ b/man7/socket.7 >> @@ -490,6 +490,26 @@ flag on a socket >> operation. >> Expects an integer boolean flag. >> .TP >> +.BR SO_INCOMING_CPU " (getsockopt since Linux 3.19, setsockopt since >> Linux 4.4)" >> +.\" getsocktop 2c8c56e15df3d4c2af3d656e44feb18789f75837 >> +.\" setsocktop 70da268b569d32a9fddeea85dc18043de9d89f89 >> +Sets or gets the cpu affinity of a socket. Expects an integer flag. >> +.sp >> +.in +4n >> +.nf >> +int cpu = 1; >> +socklen_t len = sizeof(cpu); >> +setsockopt(fd, SOL_SOCKET, SO_INCOMING_CPU, &cpu, &len); >> +.fi >> +.in >> +.sp >> +The typical use case is one listener per RX queue, as the associated listener >> +should only accept flows handled in softirq by the same cpu. This provides >> +optimal NUMA behavior and keep cpu caches hot. >> +.TP >> .B SO_KEEPALIVE >> Enable sending of keep-alive messages on connection-oriented sockets. >> Expects an integer boolean flag. > > Thank you! Patch applied. > > I have tried to enhance the description somewhat. I'm not sure whether > what I've written is quite correct (or whether it should be further > extended). Eric, could you please take a look at the following, and let > me know if anything needs fixing: > > SO_INCOMING_CPU (gettable since Linux 3.19, settable since Linux > 4.4) > Sets or gets the CPU affinity of a socket. Expects an > integer flag. > > int cpu = 1; > socklen_t len = sizeof(cpu); > setsockopt(fd, SOL_SOCKET, SO_INCOMING_CPU, &cpu, &len); > > Because all of the packets for a single stream (i.e., all > packets for the same 4-tuple) arrive on the single RX queue > that is associated with a particular CPU, the typical use > case is to employ one listening process per RX queue, with > the incoming flow being handled by a listener on the same > CPU that is handling the RX queue. This provides optimal > NUMA behavior and keeps CPU caches hot. > > Cheers, > > Michael > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
