linux-kernel - [tip:perf/core] perf record: Do not ask for precise

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Date:   Thu, 20 Jul 2017 01:50:31 -0700
From:   tip-bot for Arnaldo Carvalho de Melo <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hpa@...or.com, mingo@...nel.org, tglx@...utronix.de,
        wangnan0@...wei.com, namhyung@...nel.org, acme@...hat.com,
        jolsa@...nel.org, adrian.hunter@...el.com, dsahern@...il.com,
        linux-kernel@...r.kernel.org
Subject: [tip:perf/core] perf record: Do not ask for precise_ip with
 --no-samples

Commit-ID:  4b4cd50319127b3b606b8aaf3426d8972df1666a
Gitweb:     http://git.kernel.org/tip/4b4cd50319127b3b606b8aaf3426d8972df1666a
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Mon, 3 Jul 2017 13:26:32 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Tue, 18 Jul 2017 23:14:13 -0300

perf record: Do not ask for precise_ip with --no-samples

When the user doesn't specify an event with -e/--event, 'perf record'
will use as a default the "cycles" event with the highest level of
precision in perf_event_attr.precise_ip, but --no-samples, if present,
is incompatible with precise_ip != 0, so use the newly introduced
__perf_event__add_default(precise = false) to fix that:

Before:

  # perf record -n usleep 1
  Please consider tweaking /proc/sys/kernel/perf_event_max_sample_rate.
  Error:
  The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (cycles:ppp).
  /bin/dmesg may provide additional information.
  No CONFIG_PERF_EVENTS=y kernel support configured?
  #

After:

  # perf record -n usleep 1
  Please consider tweaking /proc/sys/kernel/perf_event_max_sample_rate.
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.018 MB perf.data ]
  [root@...et /]# perf evlist -v
  cycles: size: 112, sample_type: IP|TID|TIME|PERIOD, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1
  [root@...et /]#

Reported-by: Jiri Olsa <jolsa@...nel.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lkml.kernel.org/n/tip-q991fw6s6rhjvrd5ye4t7qom@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.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 17a14bc..64eef9a5 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1821,7 +1821,7 @@ int cmd_record(int argc, const char **argv)
 		record.opts.tail_synthesize = true;
 
 	if (rec->evlist->nr_entries == 0 &&
-	    perf_evlist__add_default(rec->evlist) < 0) {
+	    __perf_evlist__add_default(rec->evlist, !record.opts.no_samples) < 0) {
 		pr_err("Not enough memory for event selector list\n");
 		goto out;
 	}