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sched/fair: Reset nr_balance_failed after active balancing

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To force a task migration during active balancing, nr_balance_failed is set
to cache_nice_tries + 1. However nr_balance_failed is not reset. As a side
effect, the next regular load balance under the same sd, a cache hot task
might be migrated, just because nr_balance_failed count is high.

Resetting nr_balance_failed after a successful active balance ensures
that a hot task is not unreasonably migrated. This can be verified by
looking at othe number of hot task migrations reported by /proc/schedstat.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1458735884-30105-1-git-send-email-srikar@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Srikar Dronamraju 2016-03-23 17:54:44 +05:30 committed by Ingo Molnar
parent d740037fac
commit d02c071183
1 changed files with 6 additions and 6 deletions
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12
kernel/sched/fair.c
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@ -7399,10 +7399,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
&busiest->active_balance_work);
}
/*
* We've kicked active balancing, reset the failure
* counter.
*/
/* We've kicked active balancing, force task migration. */
sd->nr_balance_failed = sd->cache_nice_tries+1;
}
} else
@ -7637,10 +7634,13 @@ static int active_load_balance_cpu_stop(void *data)
schedstat_inc(sd, alb_count);
p = detach_one_task(&env);
if (p)
if (p) {
schedstat_inc(sd, alb_pushed);
else
/* Active balancing done, reset the failure counter. */
sd->nr_balance_failed = 0;
} else {
schedstat_inc(sd, alb_failed);
}
}
rcu_read_unlock();
out_unlock: