[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging-4.13] xen: credit2: fix per-entity load tracking when continuing running
commit 2c9da5f73c3a2378036c982bf0b189b34befc403 Author: Dario Faggioli <dfaggioli@xxxxxxxx> AuthorDate: Thu Jul 15 09:39:32 2021 +0200 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Thu Jul 15 09:39:32 2021 +0200 xen: credit2: fix per-entity load tracking when continuing running If we schedule, and the current vCPU continues to run, its statistical load is not properly updated, resulting in something like this, even if all the 8 vCPUs are 100% busy: (XEN) Runqueue 0: (XEN) [...] (XEN) aveload = 2097152 (~800%) (XEN) [...] (XEN) Domain: 0 w 256 c 0 v 8 (XEN) 1: [0.0] flags=2 cpu=4 credit=9996885 [w=256] load=35 (~0%) (XEN) 2: [0.1] flags=2 cpu=2 credit=9993725 [w=256] load=796 (~0%) (XEN) 3: [0.2] flags=2 cpu=1 credit=9995885 [w=256] load=883 (~0%) (XEN) 4: [0.3] flags=2 cpu=5 credit=9998833 [w=256] load=487 (~0%) (XEN) 5: [0.4] flags=2 cpu=6 credit=9998942 [w=256] load=1595 (~0%) (XEN) 6: [0.5] flags=2 cpu=0 credit=9994669 [w=256] load=22 (~0%) (XEN) 7: [0.6] flags=2 cpu=7 credit=9997706 [w=256] load=0 (~0%) (XEN) 8: [0.7] flags=2 cpu=3 credit=9992440 [w=256] load=0 (~0%) As we can see, the average load of the runqueue as a whole is, instead, computed properly. This issue would, in theory, potentially affect Credit2 load balancing logic. In practice, however, the problem only manifests (at least with these characteristics) when there is only 1 runqueue active in the cpupool, which also means there is no need to do any load-balancing. Hence its real impact is pretty much limited to wrong per-vCPU load percentages, when looking at the output of the 'r' debug-key. With this patch, the load is updated and displayed correctly: (XEN) Runqueue 0: (XEN) [...] (XEN) aveload = 2097152 (~800%) (XEN) [...] (XEN) Domain info: (XEN) Domain: 0 w 256 c 0 v 8 (XEN) 1: [0.0] flags=2 cpu=4 credit=9995584 [w=256] load=262144 (~100%) (XEN) 2: [0.1] flags=2 cpu=6 credit=9992992 [w=256] load=262144 (~100%) (XEN) 3: [0.2] flags=2 cpu=3 credit=9998918 [w=256] load=262118 (~99%) (XEN) 4: [0.3] flags=2 cpu=5 credit=9996867 [w=256] load=262144 (~100%) (XEN) 5: [0.4] flags=2 cpu=1 credit=9998912 [w=256] load=262144 (~100%) (XEN) 6: [0.5] flags=2 cpu=2 credit=9997842 [w=256] load=262144 (~100%) (XEN) 7: [0.6] flags=2 cpu=7 credit=9994623 [w=256] load=262144 (~100%) (XEN) 8: [0.7] flags=2 cpu=0 credit=9991815 [w=256] load=262144 (~100%) Signed-off-by: Dario Faggioli <dfaggioli@xxxxxxxx> Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx> master commit: 89052b9fa24bf976924e40918fc9fa3b1b940e17 master date: 2021-06-07 13:17:06 +0100 --- xen/common/sched_credit2.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c index fab6ac7aff..8ba741e379 100644 --- a/xen/common/sched_credit2.c +++ b/xen/common/sched_credit2.c @@ -3554,6 +3554,8 @@ static void csched2_schedule( runq_remove(snext); __set_bit(__CSFLAG_scheduled, &snext->flags); } + else + update_load(ops, rqd, snext, 0, now); /* Clear the idle mask if necessary */ if ( cpumask_test_cpu(sched_cpu, &rqd->idle) ) -- generated by git-patchbot for /home/xen/git/xen.git#staging-4.13
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