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Subject[PATCH 3/3] perf tools: Check maximum frequency rate for record/top
Date
Adding the check for maximum allowed frequency rate
defined in following file:
/proc/sys/kernel/perf_event_max_sample_rate

When we cross the maximum value we fail and display
detailed error message with advise.

$ perf record -F 3000 ls
Maximum frequency rate (2000) reached.
Please use -F freq option with lower value or consider
tweaking /proc/sys/kernel/perf_event_max_sample_rate.

In case user does not specify the frequency and
the default value cross the maximum, we display
warning and set the frequency value to the
current maximum.

$ perf record ls
Lowering default frequency rate to 2000.
Please consider tweaking /proc/sys/kernel/perf_event_max_sample_rate.

Same messages are used for 'perf top'.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-record.c | 15 +---------
tools/perf/builtin-top.c | 15 +---------
tools/perf/util/evlist.h | 1 +
tools/perf/util/record.c | 72 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 75 insertions(+), 28 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index ab8d15e..4eaae4b 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -929,20 +929,7 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
if (perf_evlist__create_maps(evsel_list, &rec->opts.target) < 0)
usage_with_options(record_usage, record_options);

- if (rec->opts.user_interval != ULLONG_MAX)
- rec->opts.default_interval = rec->opts.user_interval;
- if (rec->opts.user_freq != UINT_MAX)
- rec->opts.freq = rec->opts.user_freq;
-
- /*
- * User specified count overrides default frequency.
- */
- if (rec->opts.default_interval)
- rec->opts.freq = 0;
- else if (rec->opts.freq) {
- rec->opts.default_interval = rec->opts.freq;
- } else {
- ui__error("frequency and count are zero, aborting\n");
+ if (perf_opts__config(&rec->opts)) {
err = -EINVAL;
goto out_free_fd;
}
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 04f5bf2..8736cb3 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1203,20 +1203,7 @@ int cmd_top(int argc, const char **argv, const char *prefix __maybe_unused)
if (top.delay_secs < 1)
top.delay_secs = 1;

- if (opts->user_interval != ULLONG_MAX)
- opts->default_interval = opts->user_interval;
- if (opts->user_freq != UINT_MAX)
- opts->freq = opts->user_freq;
-
- /*
- * User specified count overrides default frequency.
- */
- if (opts->default_interval)
- opts->freq = 0;
- else if (opts->freq) {
- opts->default_interval = opts->freq;
- } else {
- ui__error("frequency and count are zero, aborting\n");
+ if (perf_opts__config(opts)) {
status = -EINVAL;
goto out_delete_maps;
}
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 6e8acc9..ebd6409 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -99,6 +99,7 @@ void perf_evlist__set_id_pos(struct perf_evlist *evlist);
bool perf_can_sample_identifier(void);
void perf_evlist__config(struct perf_evlist *evlist,
struct perf_record_opts *opts);
+int perf_opts__config(struct perf_record_opts *opts);

int perf_evlist__prepare_workload(struct perf_evlist *evlist,
struct perf_target *target,
diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
index 18d73aa..1569641 100644
--- a/tools/perf/util/record.c
+++ b/tools/perf/util/record.c
@@ -2,6 +2,8 @@
#include "evsel.h"
#include "cpumap.h"
#include "parse-events.h"
+#include "fs.h"
+#include "util.h"

typedef void (*setup_probe_fn_t)(struct perf_evsel *evsel);

@@ -106,3 +108,73 @@ void perf_evlist__config(struct perf_evlist *evlist,

perf_evlist__set_id_pos(evlist);
}
+
+static int get_max_rate(unsigned int *rate)
+{
+ const char *procfs;
+ char path[PATH_MAX];
+
+ procfs = procfs_find_mountpoint();
+ if (!procfs)
+ return -1;
+
+ snprintf(path, PATH_MAX,
+ "%s/sys/kernel/perf_event_max_sample_rate", procfs);
+
+ return filename__read_int(path, (int *) rate);
+}
+
+static int perf_opts__config_freq(struct perf_record_opts *opts)
+{
+ bool user_freq = opts->user_freq != UINT_MAX;
+ unsigned int max_rate;
+
+ if (opts->user_interval != ULLONG_MAX)
+ opts->default_interval = opts->user_interval;
+ if (user_freq)
+ opts->freq = opts->user_freq;
+
+ /*
+ * User specified count overrides default frequency.
+ */
+ if (opts->default_interval)
+ opts->freq = 0;
+ else if (opts->freq) {
+ opts->default_interval = opts->freq;
+ } else {
+ pr_err("frequency and count are zero, aborting\n");
+ return -1;
+ }
+
+ if (get_max_rate(&max_rate))
+ return 0;
+
+ /*
+ * User specified frequency is over current maximum.
+ */
+ if (user_freq && (max_rate < opts->freq)) {
+ pr_err("Maximum frequency rate (%u) reached.\n"
+ "Please use -F freq option with lower value or consider\n"
+ "tweaking /proc/sys/kernel/perf_event_max_sample_rate.\n",
+ max_rate);
+ return -1;
+ }
+
+ /*
+ * Default frequency is over current maximum.
+ */
+ if (max_rate < opts->freq) {
+ pr_warning("Lowering default frequency rate to %u.\n"
+ "Please consider tweaking "
+ "/proc/sys/kernel/perf_event_max_sample_rate.\n",
+ max_rate);
+ opts->freq = max_rate;
+ }
+
+ return 0;
+}
+
+int perf_opts__config(struct perf_record_opts *opts)
+{
+ return perf_opts__config_freq(opts);
+}
--
1.8.3.1


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