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

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Date:   Thu, 7 May 2020 13:44:40 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Jin Yao <yao.jin@...ux.intel.com>, jolsa@...nel.org,
        peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, Linux-kernel@...r.kernel.org,
        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 Thu, Apr 30, 2020 at 10:45:29AM +0200, Jiri Olsa escreveu:
> 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, applied.

- Arnaldo