Commit-ID: d02c071183e1c01a76811c878c8a52322201f81f Gitweb: http://git.kernel.org/tip/d02c071183e1c01a76811c878c8a52322201f81f Author: Srikar Dronamraju <sri...@linux.vnet.ibm.com> AuthorDate: Wed, 23 Mar 2016 17:54:44 +0530 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Thu, 31 Mar 2016 10:49:44 +0200
sched/fair: Reset nr_balance_failed after active balancing 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 <sri...@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mike Galbraith <efa...@gmx.de> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Rik van Riel <r...@redhat.com> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/1458735884-30105-1-git-send-email-sri...@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/sched/fair.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 0fe30e6..cbb075e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7399,10 +7399,7 @@ more_balance: &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:
