2016-08-15 17:21 GMT+08:00 Stanislaw Gruszka <sgrus...@redhat.com>: > On Mon, Aug 15, 2016 at 05:13:30PM +0800, Wanpeng Li wrote: >> 2016-08-12 20:10 GMT+08:00 Stanislaw Gruszka <sgrus...@redhat.com>: >> > Hi >> > >> > On Wed, Aug 10, 2016 at 01:26:41PM +0200, Ingo Molnar wrote: >> >> Nice detective work! I'm wondering, where do we stand if compared with a >> >> pre-6e998916dfe3 kernel? >> >> >> >> I admit this is a difficult question: 6e998916dfe3 does not revert >> >> cleanly and I >> >> suspect v3.17 does not run easily on a recent distro. Could you attempt >> >> to revert >> >> the bad effects of 6e998916dfe3 perhaps, just to get numbers - i.e. don't >> >> try to >> >> make the result correct, just see what the performance gap is, roughly. >> >> >> >> If there's still a significant gap then it might make sense to optimize >> >> this some >> >> more. >> > >> > I measured (partial) revert performance on 4.7 using mmtest instructions >> > from Giovanni and also tested some other possible fix (draft version): >> > >> > diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c >> > index 75f98c5..54fdf6d 100644 >> > --- a/kernel/sched/cputime.c >> > +++ b/kernel/sched/cputime.c >> > @@ -294,6 +294,8 @@ void thread_group_cputime(struct task_struct *tsk, >> > struct task_cputime *times) >> > unsigned int seq, nextseq; >> > unsigned long flags; >> > >> > + (void) task_sched_runtime(tsk); >> > + >> > rcu_read_lock(); >> > /* Attempt a lockless read on the first round. */ >> > nextseq = 0; >> > @@ -308,7 +310,7 @@ void thread_group_cputime(struct task_struct *tsk, >> > struct task_cputime *times) >> > task_cputime(t, &utime, &stime); >> > times->utime += utime; >> > times->stime += stime; >> > - times->sum_exec_runtime += task_sched_runtime(t); >> > + times->sum_exec_runtime += t->se.sum_exec_runtime; >> >> If this will not have updated stats for other threads? > > No, until tick/sched() on CPUs running threads.
Yeah, I think this change will result in not updated stats for other threads if they are running and before next update_curr() is called. Regards, Wanpeng Li
