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? Regards, Wanpeng Li