linux-kernel - [PATCH 1/2] perf record: Fix "--per-thread" option for hybrid machines

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Date:   Sat,  2 Jul 2022 10:35:35 +0800
From:   zhengjun.xing@...ux.intel.com
To:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...el.com, jolsa@...nel.org, namhyung@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        irogers@...gle.com, ak@...ux.intel.com, kan.liang@...ux.intel.com,
        zhengjun.xing@...ux.intel.com
Subject: [PATCH 1/2] perf record: Fix "--per-thread" option for hybrid machines

From: Zhengjun Xing <zhengjun.xing@...ux.intel.com>

Commit b91e5492f9d7 ("perf record: Add a dummy event on hybrid systems to
collect metadata records") adds a dummy event on hybrid systems to fix the
symbol "unknown" issue when the workload is created in a P-core but runs
on an E-core. When "--per-thread" is enabled, the nr_cpus is reduced to 1,
 adding a dummy event is useless for this issue, and it will also cause
"failed to mmap with 22 (Invalid argument)". This patch stops adding dummy
events when the option "--per-thread" is enabled, then the option can work
on hybrid machines.

Before:

 # ./perf record -e cycles:u --per-thread  sleep 1
 failed to mmap with 22 (Invalid argument)

After:

 # ./perf record -e cycles:u --per-thread  sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.002 MB perf.data (6 samples) ]

Fixes: b91e5492f9d7 ("perf record: Add a dummy event on hybrid systems to collect metadata records")
Signed-off-by: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
---
 tools/perf/builtin-record.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index e1edd4e98358..44ea2dd424fe 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1223,7 +1223,7 @@ static int record__open(struct record *rec)
 	 * of waiting or event synthesis.
 	 */
 	if (opts->initial_delay || target__has_cpu(&opts->target) ||
-	    perf_pmu__has_hybrid()) {
+	    (perf_pmu__has_hybrid() && !opts->target.per_thread)) {
 		pos = evlist__get_tracking_event(evlist);
 		if (!evsel__is_dummy_event(pos)) {
 			/* Set up dummy event. */
-- 
2.25.1