Messages in this thread | | | From | Nick Desaulniers <> | Date | Tue, 11 Oct 2022 14:32:11 -0700 | Subject | Re: Invalid event (cycles:pp) in per-thread mode, enable system wide with '-a'. |
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On Thu, Oct 6, 2022 at 8:56 PM Ravi Bangoria <ravi.bangoria@amd.com> wrote: > > +cc: PeterZ > > >>>>> +Ravi who may be able to say if there are any issues with the precise > >>>>> sampling on AMD. > >>>> > >>>> Afaik cvcles:pp will use IBS but it doesn't support per-task profiling > >>>> since it has no task context. Ravi is working on it.. > >>> > >>> Right. > >>> https://lore.kernel.org/lkml/20220829113347.295-1-ravi.bangoria@amd.com > >> > >> Cool, thanks for working on this Ravi. > >> > >> I'm not sure yet whether I may replace the kernel on my corporate > >> provided workstation, so I'm not sure yet I can help test that patch. > >> > >> Can you confirm that > >> $ perf record -e cycles:pp --freq=128 --call-graph lbr -- <command to profile> > >> > >> works with just that patch applied? Or is there more work required? > >> What is the status of that patch? > >> > >> For context, we had difficulty upstreaming support for instrumentation > >> based profile guided optimizations in the Linux kernel. > >> https://lore.kernel.org/lkml/CAHk-=whqCT0BeqBQhW8D-YoLLgp_eFY=8Y=9ieREM5xx0ef08w@mail.gmail.com/ > >> We'd like to be able to use either instrumentation or sampling to > >> optimize our builds. The major barrier to sample based approaches are > >> architecture / micro architecture issues with sample based profile > >> data collection, and bitrot of data processing utilities. > >> https://github.com/google/autofdo/issues/144 > > > > On existing AMD Zen2, Zen3 the following cmdline: > > $ perf record -e cycles:pp --freq=128 --call-graph lbr -- <command to profile> > > > > does not work. I see two reasons: > > > > 1. cycles:pp is likely converted into IBS op in cycle mode. > > Current kernels do not support IBS in per-thread mode. > > This is purely a kernel limitation > > Right, it's purely a kernel limitation. And below simple patch on top > of event-context rewrite patch[1] should be sufficient to make cycles:pp > working in per-process mode on AMD Zen. > > --- > diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c > index c251bc44c088..de01b5d27e40 100644 > --- a/arch/x86/events/amd/ibs.c > +++ b/arch/x86/events/amd/ibs.c > @@ -665,7 +665,7 @@ static struct perf_ibs perf_ibs_fetch = { > > static struct perf_ibs perf_ibs_op = { > .pmu = { > - .task_ctx_nr = perf_invalid_context, > + .task_ctx_nr = perf_hw_context, > > .event_init = perf_ibs_init, > .add = perf_ibs_add, > --- > > [1]: https://lore.kernel.org/lkml/20220829113347.295-1-ravi.bangoria@amd.com
Hi Ravi, I didn't see the above diff in https://lore.kernel.org/lkml/20221008062424.313-1-ravi.bangoria@amd.com/ Was there another distinct patch you were going to send for the above?
-- Thanks, ~Nick Desaulniers
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