On Fri, May 22, 2015 at 5:59 AM, Peter Zijlstra <[email protected]> wrote: > On Fri, May 22, 2015 at 05:55:32AM -0700, Stephane Eranian wrote: >> On Fri, May 22, 2015 at 5:53 AM, Peter Zijlstra <[email protected]> wrote: >> > On Fri, May 22, 2015 at 05:35:14AM -0700, Stephane Eranian wrote: >> >> On Fri, May 22, 2015 at 4:28 AM, Peter Zijlstra <[email protected]> >> >> wrote: >> >> > On Fri, May 22, 2015 at 01:21:46PM +0200, Peter Zijlstra wrote: >> >> >> @@ -821,8 +828,24 @@ int x86_schedule_events(struct cpu_hw_ev >> >> >> >> >> >> /* slow path */ >> >> >> if (i != n) { >> >> >> + int gpmax = x86_pmu.num_counters / 2; >> >> >> + >> >> >> + /* >> >> >> + * Do not allow scheduling of more than half the >> >> >> available >> >> >> + * generic counters. >> >> >> + * >> >> >> + * This helps avoid counter starvation of sibling thread >> >> >> by >> >> >> + * ensuring at most half the counters cannot be in >> >> >> exclusive >> >> >> + * mode. There is no designated counters for the limits. >> >> >> Any >> >> >> + * N/2 counters can be used. This helps with events with >> >> >> + * specific counter constraints. >> >> >> + */ >> >> >> + if (is_ht_workaround_enabled() && !cpuc->is_fake && >> >> >> + READ_ONCE(cpuc->excl_cntrs->exclusive_present)) >> >> >> + gpmax /= 2; >> >> >> + >> >> >> unsched = perf_assign_events(cpuc->event_constraint, n, >> >> >> wmin, >> >> >> - wmax, assign); >> >> >> + wmax, gpmax, assign); >> >> >> } >> >> >> >> >> > >> >> > Hmm, I divide by 2 twice.. no wonder it doesn't quite work as expected. >> >> >> >> Yes, that's what I said. Other problem is, with no watchdog, measuring >> >> a non-corrupting event is still multiplexing when more than 2 instances >> >> are passed: >> >> $ perf stat -a -C 0 -e r20cc,r20cc,r20cc,r20cc -I 1000 sleep 100 >> >> >> >> I get 50% scheduling, only 2 out of 4 events scheduled at any time. >> >> >> >> There is nothing running on the sibling thread, so it should let me run >> >> with 4 >> >> instances as per your patch. >> > >> > Ah, I limited it to n/2 if either of the siblings has an exclusive event >> > on. >> > >> But in my test case above, there was no exclusive event at all on either >> sibling and yet it limited the non-excl to 2. > > I bet you tested the exclusive events earlier :-) Its one of the bugs, > the n_excl accounting is leaking up. Once !0 it stays !0.
So you're saying intel_put_excl_constraint() does not do the --n_excl? Could it be that the flags is not showing PERF_X86_EVENT_EXCL? Cannot be related to cpuc_fake because you have it in both the ++ and -- functions. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
