Commit-ID: bb0bd044e65c2bf0f26b29613fcc441dfdeedf14 Gitweb: http://git.kernel.org/tip/bb0bd044e65c2bf0f26b29613fcc441dfdeedf14 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Mon, 10 Apr 2017 13:20:45 +0200 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Fri, 14 Apr 2017 10:26:36 +0200 sched/fair: Increase PELT accuracy for small tasks We truncate (and loose) the lower 10 bits of runtime in ___update_load_avg(), this means there's a consistent bias to under-account tasks. This is esp. significant for small tasks. Cure this by only forwarding last_update_time to the point we've actually accounted for, leaving the remainder for the next time. Reported-by: Morten Rasmussen <morten.rasmussen@xxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Acked-by: Morten Rasmussen <morten.rasmussen@xxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Mike Galbraith <efault@xxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/fair.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d43e9ac..1e3b99a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2915,7 +2915,8 @@ ___update_load_avg(u64 now, int cpu, struct sched_avg *sa, delta >>= 10; if (!delta) return 0; - sa->last_update_time = now; + + sa->last_update_time += delta << 10; /* * Now we know we crossed measurement unit boundaries. The *_avg -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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