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

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Message-ID: <20200430084529.GC1681583@krava>
Date:   Thu, 30 Apr 2020 10:45:29 +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 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


> ---
>  tools/perf/util/parse-events.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 10107747b361..786eddb6a097 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1629,12 +1629,11 @@ parse_events__set_leader_for_uncore_aliase(char *name, struct list_head *list,
>  		 * event. That can be used to distinguish the leader from
>  		 * other members, even they have the same event name.
>  		 */
> -		if ((leader != evsel) && (leader->pmu_name == evsel->pmu_name)) {
> +		if ((leader != evsel) &&
> +		    !strcmp(leader->pmu_name, evsel->pmu_name)) {
>  			is_leader = false;
>  			continue;
>  		}
> -		/* The name is always alias name */
> -		WARN_ON(strcmp(leader->name, evsel->name));
>  
>  		/* Store the leader event for each PMU */
>  		leaders[nr_pmu++] = (uintptr_t) evsel;
> -- 
> 2.17.1
>