1 files changed, 71 insertions, 0 deletions

diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
index 18d73aa2f0f8..c8845b107f60 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 +108,72 @@ void perf_evlist__config(struct perf_evlist *evlist,
 
         perf_evlist__set_id_pos(evlist);
 }
+
+static int get_max_rate(unsigned int *rate)
+{
+        char path[PATH_MAX];
+        const char *procfs = procfs__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_record_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_record_opts__config(struct perf_record_opts *opts)
+{
+        return perf_record_opts__config_freq(opts);
+}