Messages in this thread | | | Subject | Re: [PATCH] Powerpc/perf: Wire up PMI throttling | From | Ravi Bangoria <> | Date | Fri, 16 Nov 2018 15:26:17 +0530 |
| |
On 11/15/18 6:13 PM, Michael Ellerman wrote: > Ravi Bangoria <ravi.bangoria@linux.ibm.com> writes: > >> Commit 14c63f17b1fde ("perf: Drop sample rate when sampling is too >> slow") introduced a way to throttle PMU interrupts if we're spending >> too much time just processing those. Wire up powerpc PMI handler to >> use this infrastructure. > > To be clear we have throttling of the *rate* of interrupts, but this > adds throttling based on the *time taken* to process the interrupts. Or > at least that's my understanding?
Right. This throttles based on time taken to process the interrupts.
> >> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c >> index 9a86572db1ef..44f85fa22356 100644 >> --- a/arch/powerpc/kernel/traps.c >> +++ b/arch/powerpc/kernel/traps.c >> @@ -18,6 +18,7 @@ >> #include <linux/errno.h> >> #include <linux/sched.h> >> #include <linux/sched/debug.h> >> +#include <linux/sched/clock.h> >> #include <linux/kernel.h> >> #include <linux/mm.h> >> #include <linux/pkeys.h> >> @@ -1803,9 +1804,12 @@ void vsx_unavailable_tm(struct pt_regs *regs) >> >> void performance_monitor_exception(struct pt_regs *regs) >> { >> + u64 start_clock; >> __this_cpu_inc(irq_stat.pmu_irqs); >> >> + start_clock = sched_clock(); >> perf_irq(regs); >> + perf_sample_event_took(sched_clock() - start_clock); >> } > > Despite the name, perf_irq() may not actually be the perf IRQ handler :) > > It's a function pointer which might call perf or might call oprofile, or > a dummy handler. > > I don't think we should be calling perf_sample_event_took() if we're not > actually using perf, that is wasteful at best. > > So the timing logic should go in the perf specific handler I think. > ie. perf_event_interrupt().
Makes sense. I'll re-send with that change.
Thanks, Ravi
| |