From: "Falcon, Thomas" <thomas.falcon@intel.com>
To: "alexander.shishkin@linux.intel.com"
<alexander.shishkin@linux.intel.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"acme@kernel.org" <acme@kernel.org>,
"mingo@redhat.com" <mingo@redhat.com>,
"mark.rutland@arm.com" <mark.rutland@arm.com>,
"Hunter, Adrian" <adrian.hunter@intel.com>,
"namhyung@kernel.org" <namhyung@kernel.org>,
"irogers@google.com" <irogers@google.com>,
"jolsa@kernel.org" <jolsa@kernel.org>,
"kan.liang@linux.intel.com" <kan.liang@linux.intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-perf-users@vger.kernel.org"
<linux-perf-users@vger.kernel.org>,
"ak@linux.intel.com" <ak@linux.intel.com>
Subject: Re: [RESEND][PATCH v2 0/2] perf record: ratio-to-prev event term for auto counter reload
Date: Wed, 24 Sep 2025 19:09:22 +0000 [thread overview]
Message-ID: <6478744c4c07fae4b889b252248522f81359ec77.camel@intel.com> (raw)
In-Reply-To: <20250902164047.64261-1-thomas.falcon@intel.com>
On Tue, 2025-09-02 at 11:40 -0500, Thomas Falcon wrote:
> The Auto Counter Reload (ACR)[1] feature is used to track the
> relative rates of two or more perf events, only sampling
> when a given threshold is exceeded. This helps reduce overhead
> and unnecessary samples. However, enabling this feature
> currently requires setting two parameters:
Ping.
Thanks,
Tom
>
> -- Event sampling period ("period")
> -- acr_mask, which determines which events get reloaded
> when the sample period is reached.
>
> For example, in the following command:
>
> perf record -e "{cpu_atom/branch-misses,period=200000,\
> acr_mask=0x2/ppu,cpu_atom/branch-instructions,period=1000000,\
> acr_mask=0x3/u}" -- ./mispredict
>
> The goal is to limit event sampling to cases when the
> branch miss rate exceeds 20%. If the branch instructions
> sample period is exceeded first, both events are reloaded.
> If branch misses exceed their threshold first, only the
> second counter is reloaded, and a sample is taken.
>
> To simplify this, provide a new “ratio-to-prev” event term
> that works alongside the period event option or -c option.
> This would allow users to specify the desired relative rate
> between events as a ratio, making configuration more intuitive.
>
> With this enhancement, the equivalent command would be:
>
> perf record -e "{cpu_atom/branch-misses/ppu,\
> cpu_atom/branch-instructions,period=1000000,ratio_to_prev=5/u}" \
> -- ./mispredict
>
> or
>
> perf record -e "{cpu_atom/branch-misses/ppu,\
> cpu_atom/branch-instructions,ratio-to-prev=5/u}" -c 1000000 \
> -- ./mispredict
>
> [1]
> https://lore.kernel.org/lkml/20250327195217.2683619-1-kan.liang@linux.intel.com/
>
> Changes in v2 (mostly suggested by Ian Rogers):
>
> -- Add documentation explaining acr_mask bitmask used by ACR
> -- Move ACR specific implementation to arch/x86/
> -- Provide test cases for event parsing and perf record tests
>
> Thomas Falcon (2):
> perf record: Add ratio-to-prev term
> perf record: add auto counter reload parse and regression tests
>
> tools/perf/Documentation/intel-acr.txt | 53 ++++++++++++++++++
> tools/perf/Documentation/perf-list.txt | 2 +
> tools/perf/arch/x86/util/evsel.c | 53 ++++++++++++++++++
> tools/perf/tests/parse-events.c | 54 ++++++++++++++++++
> tools/perf/tests/shell/record.sh | 40 ++++++++++++++
> tools/perf/util/evsel.c | 76
> ++++++++++++++++++++++++++
> tools/perf/util/evsel.h | 1 +
> tools/perf/util/evsel_config.h | 1 +
> tools/perf/util/parse-events.c | 22 ++++++++
> tools/perf/util/parse-events.h | 3 +-
> tools/perf/util/parse-events.l | 1 +
> tools/perf/util/pmu.c | 3 +-
> 12 files changed, 307 insertions(+), 2 deletions(-)
> create mode 100644 tools/perf/Documentation/intel-acr.txt
>
next prev parent reply other threads:[~2025-09-24 19:09 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-02 16:40 [RESEND][PATCH v2 0/2] perf record: ratio-to-prev event term for auto counter reload Thomas Falcon
2025-09-02 16:40 ` [RESEND][PATCH v2 1/2] perf record: Add ratio-to-prev term Thomas Falcon
2025-09-24 21:34 ` Ian Rogers
2025-09-02 16:40 ` [RESEND][PATCH v2 2/2] perf record: Add auto counter reload parse and regression tests Thomas Falcon
2025-09-24 21:37 ` Ian Rogers
2025-09-24 19:09 ` Falcon, Thomas [this message]
2025-09-30 7:28 ` [RESEND][PATCH v2 0/2] perf record: ratio-to-prev event term for auto counter reload Mi, Dapeng
2025-10-02 15:38 ` Falcon, Thomas
2025-10-09 2:31 ` Mi, Dapeng
2025-10-02 19:35 ` Arnaldo Carvalho de Melo
2025-10-02 21:57 ` Falcon, Thomas
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