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authorPeter Zijlstra <peterz@infradead.org>2016-06-24 15:53:54 +0200
committerIngo Molnar <mingo@kernel.org>2016-06-27 11:18:36 +0200
commit7dd4912594daf769a46744848b05bd5bc6d62469 (patch)
tree410bacdb6febc36c9adaf6db1437110ecdf95c00 /kernel/sched
parentLinux 4.7-rc5 (diff)
downloadlinux-7dd4912594daf769a46744848b05bd5bc6d62469.tar.xz
linux-7dd4912594daf769a46744848b05bd5bc6d62469.zip
sched/fair: Fix effective_load() to consistently use smoothed load
Starting with the following commit: fde7d22e01aa ("sched/fair: Fix overly small weight for interactive group entities") calc_tg_weight() doesn't compute the right value as expected by effective_load(). The difference is in the 'correction' term. In order to ensure \Sum rw_j >= rw_i we cannot use tg->load_avg directly, since that might be lagging a correction on the current cfs_rq->avg.load_avg value. Therefore we use tg->load_avg - cfs_rq->tg_load_avg_contrib + cfs_rq->avg.load_avg. Now, per the referenced commit, calc_tg_weight() doesn't use cfs_rq->avg.load_avg, as is later used in @w, but uses cfs_rq->load.weight instead. So stop using calc_tg_weight() and do it explicitly. The effects of this bug are wake_affine() making randomly poor choices in cgroup-intense workloads. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: <stable@vger.kernel.org> # v4.3+ Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: fde7d22e01aa ("sched/fair: Fix overly small weight for interactive group entities") Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/fair.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bdcbeea90c95..cc48bef40cca 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -735,8 +735,6 @@ void post_init_entity_util_avg(struct sched_entity *se)
}
}
-static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
-static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
#else
void init_entity_runnable_average(struct sched_entity *se)
{
@@ -4946,19 +4944,24 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
return wl;
for_each_sched_entity(se) {
- long w, W;
+ struct cfs_rq *cfs_rq = se->my_q;
+ long W, w = cfs_rq_load_avg(cfs_rq);
- tg = se->my_q->tg;
+ tg = cfs_rq->tg;
/*
* W = @wg + \Sum rw_j
*/
- W = wg + calc_tg_weight(tg, se->my_q);
+ W = wg + atomic_long_read(&tg->load_avg);
+
+ /* Ensure \Sum rw_j >= rw_i */
+ W -= cfs_rq->tg_load_avg_contrib;
+ W += w;
/*
* w = rw_i + @wl
*/
- w = cfs_rq_load_avg(se->my_q) + wl;
+ w += wl;
/*
* wl = S * s'_i; see (2)