diff options
author | Jonathan Corbet <corbet@lwn.net> | 2019-10-29 04:43:29 -0600 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2019-10-29 04:43:29 -0600 |
commit | 822bbba0cabb50825a0ce22707dc45eb82d02853 (patch) | |
tree | ea61d4ca72cb60b4cae8e95f64eefa7cd2a36603 /kernel/sched/fair.c | |
parent | d41abfd7ae33cd3c1d9189438937d61cb75e690a (diff) | |
parent | 7d194c2100ad2a6dded545887d02754948ca5241 (diff) |
Merge tag 'v5.4-rc4' into docs-next
I need to pick up the independent changes made to
Documentation/core-api/memory-allocation.rst to be able to merge further
work without creating a total mess.
Diffstat (limited to 'kernel/sched/fair.c')
-rw-r--r-- | kernel/sched/fair.c | 36 |
1 files changed, 22 insertions, 14 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 83ab35e2374f..682a754ea3e1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4926,20 +4926,28 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) if (++count > 3) { u64 new, old = ktime_to_ns(cfs_b->period); - new = (old * 147) / 128; /* ~115% */ - new = min(new, max_cfs_quota_period); - - cfs_b->period = ns_to_ktime(new); - - /* since max is 1s, this is limited to 1e9^2, which fits in u64 */ - cfs_b->quota *= new; - cfs_b->quota = div64_u64(cfs_b->quota, old); - - pr_warn_ratelimited( - "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us %lld, cfs_quota_us = %lld)\n", - smp_processor_id(), - div_u64(new, NSEC_PER_USEC), - div_u64(cfs_b->quota, NSEC_PER_USEC)); + /* + * Grow period by a factor of 2 to avoid losing precision. + * Precision loss in the quota/period ratio can cause __cfs_schedulable + * to fail. + */ + new = old * 2; + if (new < max_cfs_quota_period) { + cfs_b->period = ns_to_ktime(new); + cfs_b->quota *= 2; + + pr_warn_ratelimited( + "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n", + smp_processor_id(), + div_u64(new, NSEC_PER_USEC), + div_u64(cfs_b->quota, NSEC_PER_USEC)); + } else { + pr_warn_ratelimited( + "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n", + smp_processor_id(), + div_u64(old, NSEC_PER_USEC), + div_u64(cfs_b->quota, NSEC_PER_USEC)); + } /* reset count so we don't come right back in here */ count = 0; |