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Don't check the result of setting SO_INCOMING_CPU

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The SO_INCOMING_CPU is available since Linux 3.19 for getting the value,
but only since Linux 4.4 for setting the value (see below for a full
description).  BIND 9 should not fail when setting the option on the
socket fails, as this is only an optimization and not hard requirement
to run BIND 9.

    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;
            setsockopt(fd, SOL_SOCKET, SO_INCOMING_CPU, &cpu, sizeof(cpu));

        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.
This commit is contained in:
Ondřej Surý 2020-06-03 11:01:19 +02:00
parent 0468454c0a
commit 4ec357da0a
1 changed files with 5 additions and 2 deletions
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7
lib/isc/netmgr/udp.c
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@ -115,9 +115,12 @@ isc_nm_listenudp(isc_nm_t *mgr, isc_nmiface_t *iface, isc_nm_recv_cb_t cb,
#endif
#ifdef SO_INCOMING_CPU
res = setsockopt(csock->fd, SOL_SOCKET, SO_INCOMING_CPU,
/* We don't check for the result, because SO_INCOMING_CPU can be
* available without the setter on Linux kernel version 4.4, and
* setting SO_INCOMING_CPU is just an optimization.
*/
(void)setsockopt(csock->fd, SOL_SOCKET, SO_INCOMING_CPU,
&(int){ 1 }, sizeof(int));
RUNTIME_CHECK(res == 0);
#endif
ievent = isc__nm_get_ievent(mgr, netievent_udplisten);
ievent->sock = csock;