Commit-ID: 24d0c1d6e65f635b2c0684d0a42ff6c0674aa0e6 Gitweb: https://git.kernel.org/tip/24d0c1d6e65f635b2c0684d0a42ff6c0674aa0e6 Author: Peter Zijlstra <[email protected]> AuthorDate: Tue, 13 Feb 2018 13:37:28 +0000 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 21 Feb 2018 08:49:42 +0100
sched/fair: Do not migrate due to a sync wakeup on exit When a task exits, it notifies the parent that it has exited. This is a sync wakeup and the exiting task may pull the parent towards the wakers CPU. For simple workloads like using a shell, it was observed that the shell is pulled across nodes by exiting processes. This is daft as the parent may be long-lived and properly placed. This patch special cases a sync wakeup on exit to avoid pulling tasks across nodes. Testing on a range of workloads and machines showed very little differences in performance although there was a small 3% boost on some machines running a shellscript intensive workload (git regression test suite). Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Mel Gorman <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Giovanni Gherdovich <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Matt Fleming <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a07920f..302dda8 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6350,7 +6350,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f int cpu = smp_processor_id(); int new_cpu = prev_cpu; int want_affine = 0; - int sync = wake_flags & WF_SYNC; + int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING); if (sd_flag & SD_BALANCE_WAKE) { record_wakee(p);
