perf top: Allow asking for the maximum allowed sample rate

tip:perf/core tip-bot for Arnaldo Carvalho de Melo 1 participant 1 message Mar 6, 2018 perf events

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2018-03-06 06:45 UTC #0 lore raw

Commit-ID:  7831bf236505bcb2a0a1255e7f3e902a0cb732d6
Gitweb:     https://git.kernel.org/tip/7831bf236505bcb2a0a1255e7f3e902a0cb732d6
Author:     Arnaldo Carvalho de Melo <[email protected]>
AuthorDate: Thu, 1 Mar 2018 14:25:56 -0300
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 5 Mar 2018 09:58:44 -0300

perf top: Allow asking for the maximum allowed sample rate

Add the handy '-F max' shortcut, just introduced to 'perf record', to reading and using the kernel.perf_event_max_sample_rate value as the user supplied sampling frequency:

Cc Adrian Hunter <[email protected]>

Cc David Ahern <[email protected]>

Cc Jiri Olsa <[email protected]>

Cc Namhyung Kim <[email protected]>

Cc Wang Nan <[email protected]>

Link https://lkml.kernel.org/n/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/Documentation/perf-top.txt | 4 +++-
 tools/perf/builtin-top.c              | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

tools/perf/Documentation/perf-top.txt +3 -1

index 8a32cc77bead..a039407d63b8 100644
@@ -55,7 +55,9 @@ Default is to monitor all CPUS.
 
 -F <freq>::
 --freq=<freq>::
-	Profile at this frequency.
+	Profile at this frequency. Use 'max' to use the currently maximum
+	allowed frequency, i.e. the value in the kernel.perf_event_max_sample_rate
+	sysctl.
 
 -i::
 --inherit::

tools/perf/builtin-top.c +3 -1

index 35ac016fcb98..bb4f9fafd11d 100644
@@ -1307,7 +1307,9 @@ int cmd_top(int argc, const char **argv)
 	OPT_STRING(0, "sym-annotate", &top.sym_filter, "symbol name",
 		    "symbol to annotate"),
 	OPT_BOOLEAN('z', "zero", &top.zero, "zero history across updates"),
-	OPT_UINTEGER('F', "freq", &opts->user_freq, "profile at this frequency"),
+	OPT_CALLBACK('F', "freq", &top.record_opts, "freq or 'max'",
+		     "profile at this frequency",
+		      record__parse_freq),
 	OPT_INTEGER('E', "entries", &top.print_entries,
 		    "display this many functions"),
 	OPT_BOOLEAN('U', "hide_user_symbols", &top.hide_user_symbols,