linux-kernel - Re: [PATCH] perf parse-events: Use strcmp to compare the PMU name

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Message-ID: <20200506234636.GC5377@kernel.org>
Date:   Wed, 6 May 2020 20:46:36 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Jiri Olsa <jolsa@...hat.com>, "Jin, Yao" <yao.jin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <Linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>, kan.liang@...el.com,
        yao.jin@...el.com, John Garry <john.garry@...wei.com>
Subject: Re: [PATCH] perf parse-events: Use strcmp to compare the PMU name

Em Wed, May 06, 2020 at 03:45:59PM -0700, Ian Rogers escreveu:
> On Thu, Apr 30, 2020 at 8:33 AM Jiri Olsa <jolsa@...hat.com> wrote:
> >
> > On Thu, Apr 30, 2020 at 09:45:14PM +0800, Jin, Yao wrote:
> > > Hi Jiri,
> > >
> > > On 4/30/2020 4:45 PM, Jiri Olsa wrote:
> > > > On Thu, Apr 30, 2020 at 08:36:18AM +0800, Jin Yao wrote:
> > > > > A big uncore event group is split into multiple small groups which
> > > > > only include the uncore events from the same PMU. This has been
> > > > > supported in the commit 3cdc5c2cb924a ("perf parse-events: Handle
> > > > > uncore event aliases in small groups properly").
> > > > >
> > > > > If the event's PMU name starts to repeat, it must be a new event.
> > > > > That can be used to distinguish the leader from other members.
> > > > > But now it only compares the pointer of pmu_name
> > > > > (leader->pmu_name == evsel->pmu_name).
> > > > >
> > > > > If we use "perf stat -M LLC_MISSES.PCIE_WRITE -a" on cascadelakex,
> > > > > the event list is:
> > > > >
> > > > > evsel->name                                       evsel->pmu_name
> > > > > ---------------------------------------------------------------
> > > > > unc_iio_data_req_of_cpu.mem_write.part0           uncore_iio_4 (as leader)
> > > > > unc_iio_data_req_of_cpu.mem_write.part0           uncore_iio_2
> > > > > unc_iio_data_req_of_cpu.mem_write.part0           uncore_iio_0
> > > > > unc_iio_data_req_of_cpu.mem_write.part0           uncore_iio_5
> > > > > unc_iio_data_req_of_cpu.mem_write.part0           uncore_iio_3
> > > > > unc_iio_data_req_of_cpu.mem_write.part0           uncore_iio_1
> > > > > unc_iio_data_req_of_cpu.mem_write.part1           uncore_iio_4
> > > > > ......
> > > > >
> > > > > For the event "unc_iio_data_req_of_cpu.mem_write.part1" with
> > > > > "uncore_iio_4", it should be the event from PMU "uncore_iio_4".
> > > > > It's not a new leader for this PMU.
> > > > >
> > > > > But if we use "(leader->pmu_name == evsel->pmu_name)", the check
> > > > > would be failed and the event is stored to leaders[] as a new
> > > > > PMU leader.
> > > > >
> > > > > So this patch uses strcmp to compare the PMU name between events.
> > > > >
> > > > > Fixes: 3cdc5c2cb924a ("perf parse-events: Handle uncore event aliases in small groups properly")
> > > > > Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
> > > >
> > > > looks good, any chance we could have automated test
> > > > for this uncore leader setup logic? like maybe the way
> > > > John did the pmu-events tests? like test will trigger
> > > > only when there's the pmu/events in the system
> > > >
> > > > Acked-by: Jiri Olsa <jolsa@...hat.com>
> > > >
> > > > thanks,
> > > > jirka
> > > >
> > > >
> > >
> > > I'm considering to use LKP to do the sanity tests for all perf events
> > > (core/uncore) and perf metrics periodically. It may help us to find the
> > > regressions on time.
> >
> > sounds good ;) thanks
> >
> > jirka
> 
> I've tested this and would be happy to see this merged. John's bisect
> found a memory leak fix of mine as the culprit.
> 
> Wrt testing, libbpf is using github/travis CI:
> https://github.com/libbpf/libbpf
> https://travis-ci.org/libbpf/libbpf
> Perhaps that kind of set up can automate testing and lower the
> reviewer burden - but there's upfront cost in setting it up.

Well, if someone wants to bear this upfront cost, I can provide all the
Dockerfiles + scripts I have to build those images, etc, I just don't
have the time right now to invest in learning about travis, etc.

That would be awesome.

But if people run:

make -C tools/perf build-test

And:

perf test

Before sending pull requests, that would as well be fantastic :)

- Arnaldo