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Message-Id: <20240712170339.185824-3-dapeng1.mi@linux.intel.com>
Date: Fri, 12 Jul 2024 17:03:36 +0000
From: Dapeng Mi <dapeng1.mi@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Kan Liang <kan.liang@...ux.intel.com>
Cc: linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org,
Yongwei Ma <yongwei.ma@...el.com>,
Dapeng Mi <dapeng1.mi@...el.com>,
Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [Patch v3 2/5] perf x86/topdown: Correct leader selection with sample_read enabled
Addresses an issue where, in the absence of a topdown metrics event
within a sampling group, the slots event was incorrectly bypassed as
the sampling leader when sample_read was enabled.
perf record -e '{slots,branches}:S' -c 10000 -vv sleep 1
In this case, the slots event should be sampled as leader but the
branches event is sampled in fact like the verbose output shows.
perf_event_attr:
type 4 (cpu)
size 168
config 0x400 (slots)
sample_type IP|TID|TIME|READ|CPU|IDENTIFIER
read_format ID|GROUP|LOST
disabled 1
sample_id_all 1
exclude_guest 1
------------------------------------------------------------
sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 5
------------------------------------------------------------
perf_event_attr:
type 0 (PERF_TYPE_HARDWARE)
size 168
config 0x4 (PERF_COUNT_HW_BRANCH_INSTRUCTIONS)
{ sample_period, sample_freq } 10000
sample_type IP|TID|TIME|READ|CPU|IDENTIFIER
read_format ID|GROUP|LOST
sample_id_all 1
exclude_guest 1
The sample period of slots event instead of branches event is reset to
0.
This fix ensures the slots event remains the leader under these
conditions.
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
---
tools/perf/arch/x86/util/topdown.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/tools/perf/arch/x86/util/topdown.c b/tools/perf/arch/x86/util/topdown.c
index 49f25d67ed77..857e00cf579f 100644
--- a/tools/perf/arch/x86/util/topdown.c
+++ b/tools/perf/arch/x86/util/topdown.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0
#include "api/fs/fs.h"
#include "util/evsel.h"
+#include "util/evlist.h"
#include "util/pmu.h"
#include "util/pmus.h"
#include "util/topdown.h"
@@ -87,11 +88,22 @@ bool arch_is_topdown_metrics(const struct evsel *evsel)
*/
bool arch_topdown_sample_read(struct evsel *leader)
{
+ struct evsel *evsel;
+
if (!evsel__sys_has_perf_metrics(leader))
return false;
- if (arch_is_topdown_slots(leader))
- return true;
+ if (!arch_is_topdown_slots(leader))
+ return false;
+
+ /*
+ * If slots event as leader event but no topdown metric events
+ * in group, slots event should still sample as leader.
+ */
+ evlist__for_each_entry(leader->evlist, evsel) {
+ if (evsel != leader && arch_is_topdown_metrics(evsel))
+ return true;
+ }
return false;
}
--
2.40.1
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