From: Ian Rogers <irogers@google.com>
To: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: peterz@infradead.org, acme@kernel.org, jolsa@kernel.org,
namhyung@kernel.org, bp@alien8.de, x86@kernel.org,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
sandipan.das@amd.com, ananth.narayan@amd.com,
santosh.shukla@amd.com
Subject: Re: [PATCH] perf/amd: Prevent grouping of IBS events
Date: Wed, 21 Jun 2023 22:09:18 -0700 [thread overview]
Message-ID: <CAP-5=fXfTDY9-uDq2BR2QmTP=-1=4RKRK=dvKmz5CF+oXgz+Eg@mail.gmail.com> (raw)
In-Reply-To: <3b0abd4a-6450-c282-65ff-ec0c7df67b03@amd.com>
On Tue, Jun 20, 2023 at 8:27 PM Ravi Bangoria <ravi.bangoria@amd.com> wrote:
>
> Hi Ian,
>
> On 20-Jun-23 10:14 PM, Ian Rogers wrote:
> > On Tue, Jun 20, 2023 at 2:16 AM Ravi Bangoria <ravi.bangoria@amd.com> wrote:
> >>
> >> IBS PMUs can have only one event active at any point in time. Restrict
> >> grouping of multiple IBS events.
> >
> > Thanks Ravi,
> >
> > can you provide an example/test for this? Should this be a weak group issue?
>
> Before:
> $ sudo ./perf record -e "{ibs_op//,ibs_op//}" -C 0
> ^C[ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.540 MB perf.data (531 samples) ]
>
> After:
> $ sudo ./perf record -e "{ibs_op//,ibs_op//}" -C 0
> Error:
> AMD IBS may only be available in system-wide/per-cpu mode.
> Try using -a, or -C and workload affinity
>
> The error message is stale and misleading. I have a patch to fix it.
> I'll post it separately.
Thanks Ravi, so this is a workaround for a PMU driver bug where the
perf_event_open should have failed for the sibling event?
The behavior is somewhat reminiscent of arch_evsel__must_be_in_group:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/arch/x86/util/evsel.c?h=perf-tools-next#n41
Normally software events would be valid in the group, should the code
ignore these?
Thanks,
Ian
> Thanks,
> Ravi
next prev parent reply other threads:[~2023-06-22 5:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-20 9:16 [PATCH] perf/amd: Prevent grouping of IBS events Ravi Bangoria
2023-06-20 16:44 ` Ian Rogers
2023-06-21 3:27 ` Ravi Bangoria
2023-06-21 6:23 ` [PATCH] perf evsel amd: Fix IBS error message Ravi Bangoria
2023-06-21 22:33 ` Namhyung Kim
2023-06-22 5:27 ` Ravi Bangoria
2023-06-22 5:38 ` Namhyung Kim
2023-06-21 22:50 ` [PATCH] perf/amd: Prevent grouping of IBS events Namhyung Kim
2023-06-22 3:30 ` Ravi Bangoria
2023-06-22 5:09 ` Ian Rogers [this message]
2023-06-22 5:39 ` Ravi Bangoria
2023-06-22 5:44 ` Ian Rogers
2023-06-22 5:49 ` Ravi Bangoria
2023-07-10 8:37 ` [tip: perf/core] " tip-bot2 for Ravi Bangoria
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