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

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Date:   Thu, 30 Apr 2020 17:32:53 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Jin, Yao" <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, 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

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