Hi Eric, [reodering for clarity] >> 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. > Hi Michael > > Sorry for the delay. Thanks for the reply, but I think you are assuming I know more than I do. I'd like you to elaborate a little please. See below. > Note that setting the option is not supported if SO_REUSEPORT is used. Please define "not supported". Does this yield an API diagnostic? If so, what is it? > Socket will be selected from an array, either by a hash or BPF program > that has no access to this information. Sorry -- I'm lost here. How does this comment relate to the proposed man page text above? Thanks, 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
