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

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Message-Id: <20200430003618.17002-1-yao.jin@linux.intel.com>
Date:   Thu, 30 Apr 2020 08:36:18 +0800
From:   Jin Yao <yao.jin@...ux.intel.com>
To:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com
Cc:     Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com,
        Jin Yao <yao.jin@...ux.intel.com>
Subject: [PATCH] perf parse-events: Use strcmp to compare the PMU name

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>
---
 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