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sched/fair: Rewrite cfs_rq->removed_*avg

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Since on wakeup migration we don't hold the rq->lock for the old CPU
we cannot update its state. Instead we add the removed 'load' to an
atomic variable and have the next update on that CPU collect and
process it.

Currently we have 2 atomic variables; which already have the issue
that they can be read out-of-sync. Also, two atomic ops on a single
cacheline is already more expensive than an uncontended lock.

Since we want to add more, convert the thing over to an explicit
cacheline with a lock in.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-05-08 16:51:41 +02:00 • committed by Ingo Molnar
parent 9059393e4e
commit 2a2f5d4e44
3 changed files with 48 additions and 24 deletions
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8
kernel/sched/debug.c
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@ -564,10 +564,10 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
cfs_rq->runnable_load_avg);
SEQ_printf(m, " .%-30s: %lu\n", "util_avg",
cfs_rq->avg.util_avg);
SEQ_printf(m, " .%-30s: %ld\n", "removed_load_avg",
atomic_long_read(&cfs_rq->removed_load_avg));
SEQ_printf(m, " .%-30s: %ld\n", "removed_util_avg",
atomic_long_read(&cfs_rq->removed_util_avg));
SEQ_printf(m, " .%-30s: %ld\n", "removed.load_avg",
cfs_rq->removed.load_avg);
SEQ_printf(m, " .%-30s: %ld\n", "removed.util_avg",
cfs_rq->removed.util_avg);
#ifdef CONFIG_FAIR_GROUP_SCHED
SEQ_printf(m, " .%-30s: %lu\n", "tg_load_avg_contrib",
cfs_rq->tg_load_avg_contrib);