From: Namhyung Kim <namhyung@kernel.org>
To: "Liang, Kan" <kan.liang@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>, Carel Si <beibei.si@intel.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
alexandre.torgue@foss.st.com, Andi Kleen <ak@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>, James Clark <james.clark@arm.com>,
Jiri Olsa <jolsa@kernel.org>, John Garry <john.garry@huawei.com>,
Mark Rutland <mark.rutland@arm.com>,
mcoquelin.stm32@gmail.com, Peter Zijlstra <peterz@infradead.org>,
Stephane Eranian <eranian@google.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, lkp@lists.01.org,
kbuild test robot <lkp@intel.com>
Subject: Re: [LKP] Re: [perf vendor events] 3f5f0df7bf: perf-sanity-tests.perf_all_metrics_test.fail
Date: Thu, 14 Apr 2022 15:58:52 -0700 [thread overview]
Message-ID: <CAM9d7cic6AhJGrNF7wmyowUBpp0mPu8TdiVebL4XXcotFtLUuQ@mail.gmail.com> (raw)
In-Reply-To: <f020f05e-0e54-cc59-0666-810cf3a4fd14@linux.intel.com>
Hi Kan,
On Thu, Apr 14, 2022 at 12:06 PM Liang, Kan <kan.liang@linux.intel.com> wrote:
>
>
>
> On 4/14/2022 12:09 PM, Ian Rogers wrote:
> > ```
> > $ perf stat -e '{BR_INST_RETIRED.NEAR_CALL,BR_INST_RETIRED.NEAR_TAKEN,BR_INST_RETIRED.NOT_TAKEN,cycles,cycles}:W'
> > -a sleep 1
> > Performance counter stats for 'system wide':
> >
> > <not counted> BR_INST_RETIRED.NEAR_CALL
> > (0.00%)
> > <not counted> BR_INST_RETIRED.NEAR_TAKEN
> > (0.00%)
> > <not counted> BR_INST_RETIRED.NOT_TAKEN
> > (0.00%)
> > <not counted> cycles
> > (0.00%)
> > <not counted> cycles
> > (0.00%)
> >
> > 1.005599088 seconds time elapsed
> >
> > Some events weren't counted. Try disabling the NMI watchdog:
> > echo 0 > /proc/sys/kernel/nmi_watchdog
> > perf stat ...
> > echo 1 > /proc/sys/kernel/nmi_watchdog
> > The events in group usually have to be from the same PMU. Try
> > reorganizing the group.
> > ```
> >
> > If we add two extra cycles or the original group is smaller then it is "fixed":
> > ```
> > $ perf stat -e '{BR_INST_RETIRED.NEAR_CALL,BR_INST_RETIRED.NEAR_TAKEN,BR_INST_RETIRED.NOT_TAKEN,cycles}:W'
> > -a sleep 1
> >
> > Performance counter stats for 'system wide':
> >
> > 20,378,789 BR_INST_RETIRED.NEAR_CALL
> > 168,420,963 BR_INST_RETIRED.NEAR_TAKEN
> > 96,330,608 BR_INST_RETIRED.NOT_TAKEN
> > 1,652,230,042 cycles
> >
> > 1.008757590 seconds time elapsed
> >
> > $ perf stat -e '{BR_INST_RETIRED.NEAR_CALL,BR_INST_RETIRED.NEAR_TAKEN,BR_INST_RETIRED.NOT_TAKEN,cycles,cycles,cycles}:W'
> > -a sleep 1
> >
> > Performance counter stats for 'system wide':
> >
> > 37,696,638 BR_INST_RETIRED.NEAR_CALL
> > (66.62%)
> > 298,535,151 BR_INST_RETIRED.NEAR_TAKEN
> > (66.63%)
> > 297,011,663 BR_INST_RETIRED.NOT_TAKEN
> > (66.63%)
> > 3,155,711,474 cycles
> > (66.65%)
> > 3,194,919,959 cycles
> > (66.74%)
> > 3,126,664,102 cycles
> > (66.72%)
> >
> > 1.006237962 seconds time elapsed
> > ```
> >
> > So the extra cycles is needed to fix weak groups when the nmi watchdog
> > is enabled and the group is an architecture dependent size.
>
> Yes, the size of the group depends on the architecture, but perf tool
> doesn't need to know the HW details. For this case, perf tool just sends
> the request with an extra cycles event in the group and lets kernel decide.
I prefer doing this in the kernel even if it'd be incomplete.
For the NMI watchdog, is it possible to check if it's enabled
at the moment, and set the fake_cpuc->idxmsk to prevent
scheduling events in validate_group()?
Thanks,
Namhyung
next prev parent reply other threads:[~2022-04-14 22:59 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-04 8:33 [perf vendor events] 3f5f0df7bf: perf-sanity-tests.perf_all_metrics_test.fail kernel test robot
2022-03-04 18:10 ` Ian Rogers
2022-04-13 7:05 ` [LKP] " Carel Si
2022-04-13 16:03 ` Ian Rogers
2022-04-13 16:37 ` Liang, Kan
2022-04-13 17:09 ` Ian Rogers
2022-04-13 18:17 ` Liang, Kan
2022-04-14 16:09 ` Ian Rogers
2022-04-14 19:06 ` Liang, Kan
2022-04-14 22:58 ` Namhyung Kim [this message]
2022-04-18 12:42 ` Liang, Kan
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