On Wed, 2017-04-19 at 15:20 +0200, Michael Kerrisk (man-pages) wrote: > Ping Eric! > > Would you have a chance to review the proposed text below, please. > > Thanks, > Hi Michael Sorry for the delay. Note that setting the option is not supported if SO_REUSEPORT is used. Socket will be selected from an array, either by a hash or BPF program that has no access to this information. 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 > > > > -- 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
