Messages in this thread | | | From | Nick Desaulniers <> | Date | Fri, 23 Jun 2023 09:23:38 -0700 | Subject | Re: Invalid event (cycles:pp) in per-thread mode, enable system wide with '-a'. |
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On Tue, Oct 11, 2022 at 10:05 PM Ravi Bangoria <ravi.bangoria@amd.com> wrote: > > On 12-Oct-22 9:36 AM, Ravi Bangoria wrote: > > On 12-Oct-22 3:02 AM, Nick Desaulniers wrote: > >> 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? > > > > Yes Nick. I was planning to send it once the rewrite stuff goes in. > > Hi Nick, > > Since you have practical use case, would it be possible to run your workflow > with perf rewrite and IBS patches applied? It will help us in finding/fixing > more bugs and upstreaming these changes.
Hi Ravi, Sorry, I'm not able to load a custom kernel image on my employer provided workstation, and I never got approval to expense hardware for testing this otherwise.
Was there ever any update on this? I'm on 6.1.25 now and still cant run $ perf record -e cycles:pp --call-graph lbr <any command to profile> $ cat /proc/cpuinfo ... model name : AMD Ryzen Threadripper PRO 3995WX 64-Cores ... -- Thanks, ~Nick Desaulniers
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