On Tue, Jun 27, 2017 at 08:49:19PM +0000, Liang, Kan wrote: > > > On Mon, Jun 26, 2017 at 04:19:27PM -0400, Don Zickus wrote: > > > On Fri, Jun 23, 2017 at 11:50:25PM +0200, Thomas Gleixner wrote: > > > > On Fri, 23 Jun 2017, Don Zickus wrote: > > > > > Hmm, all this work for a temp fix. Kan, how much longer until the > > > > > real fix of having perf count the right cycles? > > > > > > > > Quite a while. The approach is wilfully breaking the user space ABI, > > > > which is not going to happen. > > > > > > > > And there is a simpler solution as well, as I said here: > > > > > > > > > > > > http://lkml.kernel.org/r/alpine.DEB.2.20.1706221730520.1885@nanos > > > > > > Hi Thomas, > > > > > > So, you are saying instead of slowing down the perf counter, speed up > > > the hrtimer to sample more frequently like so: > > > > > > diff --git a/kernel/watchdog.c b/kernel/watchdog.c index > > > 03e0b69..8ff49de 100644 > > > --- a/kernel/watchdog.c > > > +++ b/kernel/watchdog.c > > > @@ -160,7 +160,7 @@ static void set_sample_period(void) > > > * and hard thresholds) to increment before the > > > * hardlockup detector generates a warning > > > */ > > > - sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5); > > > + sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / > > 10); > > > } > > > > Hi Kan, > > > > Will the above patch work for you? > > > > I haven't heard back any test result yet. > > The above patch looks good to me. > But I'm not sure if /10 is enough. We may need /15. > Anyway, I think we will test /10 first. > > Which workaround do you prefer, the above one or the one checking timestamp? Let's go with this one, it is simpler. Cheers, Don