Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

[linux.git] / kernel / sched / fair.c

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 83ab35e2374f632e0211029d7e1baa70150c388a..682a754ea3e1a867e7b1c0cb2c8dee0dfc5c1461 100644 (file)
--- 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;