On Tue, Aug 6, 2019 at 2:14 PM Robin Murphy <robin.murphy@xxxxxxx> wrote: > > On 2019-08-06 9:52 pm, Vasily Khoruzhick wrote: > > On Tue, Aug 6, 2019 at 1:19 PM Harald Geyer <harald@xxxxxxxxx> wrote: > >> > >> Vasily Khoruzhick writes: > >>> On Tue, Aug 6, 2019 at 7:35 AM Robin Murphy <robin.murphy@xxxxxxx> wrote: > >>>> > >>>> On 06/08/2019 15:01, Vasily Khoruzhick wrote: > >>>>> Looks like PMU in A64 is broken, it generates no interrupts at all and > >>>>> as result 'perf top' shows no events. > >>>> > >>>> Does something like 'perf stat sleep 1' at least count cycles correctly? > >>>> It could well just be that the interrupt numbers are wrong... > >>> > >>> Looks like it does, at least result looks plausible: > >> > >> I'm using perf stat regularly (cache benchmarks) and it works fine. > >> > >> Unfortunately I wasn't aware that perf stat is a poor test for > >> the interrupts part of the node, when I added it. So I'm not too > >> surprised I got it wrong. > >> > >> However, it would be unfortunate if the node got removed completely, > >> because perf stat would not work anymore. Maybe we can only remove > >> the interrupts or just fix them even if the HW doesn't work? > > > > I'm not familiar with PMU driver. Is it possible to get it working > > without interrupts? > > Yup - you get a grumpy message from the driver, it will refuse sampling > events (the ones which weren't working anyway), and if you measure > anything for long enough that a counter overflows you'll get wonky > results. But for counting hardware events over relatively short periods > it'll still do the job. I tried to drop interrupts completely from the node but 'perf top' is still broken. Though now in different way: it complains "cycles: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat'" Is there any way to make it working? > > Robin.
