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sched/fair: Don't increase sd->balance_interval on newidle balance
[ Upstream commit3f130a37c4
] When load_balance() fails to move some load because of task affinity, we end up increasing sd->balance_interval to delay the next periodic balance in the hopes that next time we look, that annoying pinned task(s) will be gone. However, idle_balance() pays no attention to sd->balance_interval, yet it will still lead to an increase in balance_interval in case of pinned tasks. If we're going through several newidle balances (e.g. we have a periodic task), this can lead to a huge increase of the balance_interval in a very small amount of time. To prevent that, don't increase the balance interval when going through a newidle balance. This is a similar approach to what is done in commit58b26c4c02
("sched: Increment cache_nice_tries only on periodic lb"), where we disregard newidle balance and rely on periodic balance for more stable results. Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Dietmar.Eggemann@arm.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: patrick.bellasi@arm.com Cc: vincent.guittot@linaro.org Link: http://lkml.kernel.org/r/1537974727-30788-2-git-send-email-valentin.schneider@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 11 additions and 2 deletions
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@ -7950,13 +7950,22 @@ static int load_balance(int this_cpu, struct rq *this_rq,
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sd->nr_balance_failed = 0;
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out_one_pinned:
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ld_moved = 0;
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/*
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* idle_balance() disregards balance intervals, so we could repeatedly
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* reach this code, which would lead to balance_interval skyrocketting
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* in a short amount of time. Skip the balance_interval increase logic
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* to avoid that.
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*/
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if (env.idle == CPU_NEWLY_IDLE)
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goto out;
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/* tune up the balancing interval */
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if (((env.flags & LBF_ALL_PINNED) &&
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sd->balance_interval < MAX_PINNED_INTERVAL) ||
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(sd->balance_interval < sd->max_interval))
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sd->balance_interval *= 2;
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ld_moved = 0;
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out:
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return ld_moved;
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}
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