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. Stanislaw
