linux-kernel - Re: [PATCH v3 04/15] perf/x86/amd: Support PERF_SAMPLE_{WEIGHT|WEIGHT

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Date:   Thu, 29 Sep 2022 22:09:03 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ravi Bangoria <ravi.bangoria@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>, Joe Mario <jmario@...hat.com>,
        Leo Yan <leo.yan@...aro.org>, alisaidi@...zon.com,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        dave.hansen@...ux.intel.com, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Sandipan Das <sandipan.das@....com>, ananth.narayan@....com,
        Kim Phillips <kim.phillips@....com>, santosh.shukla@....com
Subject: Re: [PATCH v3 04/15] perf/x86/amd: Support PERF_SAMPLE_{WEIGHT|WEIGHT_STRUCT}

On Wed, Sep 28, 2022 at 2:59 AM Ravi Bangoria <ravi.bangoria@....com> wrote:
>
> IbsDcMissLat indicates the number of clock cycles from when a miss is
> detected in the data cache to when the data was delivered to the core.
> Similarly, IbsTagToRetCtr provides number of cycles from when the op
> was tagged to when the op was retired. Consider these fields for
> sample->weight.
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
> ---
> Note:
> While opening a new event, perf tool starts with a set of attributes
> and goes on reverting some attributes in a predefined order until it
> succeeds or run out or all attempts. Here, 1st attempt includes both
> WEIGHT_STRUCT and exclude_guest which always fails because IBS does
> not support guest filtering. The problem however is, perf reverts
> WEIGHT_STRUCT but keeps trying with exclude_guest. Thus, although,
> this patch enables WEIGHT_STRUCT support from kernel, using it from
> the perf tool needs more changes(not included in this series).

Yeah, it'd be nice if kernel could expose more pmu capabilities like
no-exclude then tools can skip setting it for them.

Thanks,
Namhyung