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perf evlist: Warn when 'sleep' workload is used without system-wide (-a) option

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A common mistake when trying to record system-wide profiles for a given
duration is running commands like 'perf record sleep 1' or 'perf stat
sleep 1' without passing '-a' / '--all-cpus'. When '-a' is omitted, perf
defaults to per-process monitoring of the sleep process itself, which
does not collect system-wide activity and records very few events.

Add a warning in evlist__prepare_workload() when the workload executable
is 'sleep' and system-wide mode is not enabled.

Assisted-by: Antigravity:gemini-3.6-flash
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Ian Rogers 2026-08-05 21:14:14 -07:00 committed by Namhyung Kim
parent 16e113d46d
commit 78148c8529
1 changed files with 15 additions and 0 deletions
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15
tools/perf/util/evlist.c
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@ -11,6 +11,7 @@
#include <inttypes.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <linux/bitops.h>
@ -1562,6 +1563,20 @@ int evlist__prepare_workload(struct evlist *evlist, struct target *target, const
int child_ready_pipe[2], go_pipe[2];
char bf;
if (target__none(target)) {
const char *cmd = strrchr(argv[0], '/');
if (cmd)
cmd++;
else
cmd = argv[0];
if (!strcmp(cmd, "sleep")) {
ui__warning("workload '%s' specified without the system-wide (-a) option\n",
cmd);
}
}
evlist__set_workload_cork_fd(evlist, -1);
if (pipe(child_ready_pipe) < 0) {