[PATCH v3] perf record: Add support for limit perf output file size

[Jiwei Sun]

The patch adds a new option to limit the output file size, then based
on it, we can create a wrapper of the perf command that uses the option
to avoid exhausting the disk space by the unconscious user.

Testing it:

  # ./perf record -a --max-size 100M
  Couldn't synthesize bpf events.
  WARNING: The perf data has already reached the limit, stop recording!
  WARNING: The perf data has already reached the limit, stop recording!
  WARNING: The perf data has already reached the limit, stop recording!
  WARNING: The perf data has already reached the limit, stop recording!
  WARNING: The perf data has already reached the limit, stop recording!
  WARNING: The perf data has already reached the limit, stop recording!
  WARNING: The perf data has already reached the limit, stop recording!
  WARNING: The perf data has already reached the limit, stop recording!
  [ perf record: Woken up 392 times to write data ]
  [ perf record: Captured and wrote 100.104 MB perf.data (2128267 samples) ]
  Terminated

  # ls -lh perf.data
  -rw------- 1 root root 101M Mar 11 14:48 perf.data

Signed-off-by: Jiwei Sun <jiwei.sun@xxxxxxxxxxxxx>
---
v3 changes:
  - add a test result
  - add the new option to tools/perf/Documentation/perf-record.txt

v2 changes:
  - make patch based on latest Arnaldo's perf/core,
  - display warning message when reached the limit.
---
 tools/perf/Documentation/perf-record.txt |  3 ++
 tools/perf/builtin-record.c              | 42 ++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 8f0c2be34848..731dcfabe7fa 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -524,6 +524,9 @@ config terms. For example: 'cycles/overwrite/' and 'instructions/no-overwrite/'.
 
 Implies --tail-synthesize.
 
+--max-size::
+Limit the output data max size.
+
 SEE ALSO
 --------
 linkperf:perf-stat[1], linkperf:perf-list[1]
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index a468d882e74f..fe0e87781841 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -83,6 +83,7 @@ struct record {
 	struct switch_output	switch_output;
 	unsigned long long	samples;
 	cpu_set_t		affinity_mask;
+	unsigned long		output_max_size;	/* = 0: unlimited */
 };
 
 static volatile int auxtrace_record__snapshot_started;
@@ -112,6 +113,12 @@ static bool switch_output_time(struct record *rec)
 	       trigger_is_ready(&switch_output_trigger);
 }
 
+static bool record__output_max_size_exceeded(struct record *rec)
+{
+	return (rec->output_max_size &&
+	       rec->bytes_written >= rec->output_max_size);
+}
+
 static int record__write(struct record *rec, struct perf_mmap *map __maybe_unused,
 			 void *bf, size_t size)
 {
@@ -124,6 +131,12 @@ static int record__write(struct record *rec, struct perf_mmap *map __maybe_unuse
 
 	rec->bytes_written += size;
 
+	if (record__output_max_size_exceeded(rec)) {
+		pr_warning("WARNING: The perf data has already reached "
+			   "the limit, stop recording!\n");
+		raise(SIGTERM);
+	}
+
 	if (switch_output_size(rec))
 		trigger_hit(&switch_output_trigger);
 
@@ -1672,6 +1685,33 @@ static int record__parse_affinity(const struct option *opt, const char *str, int
 	return 0;
 }
 
+static int parse_output_max_size(const struct option *opt,
+				 const char *str, int unset)
+{
+	unsigned long *s = (unsigned long *)opt->value;
+	static struct parse_tag tags_size[] = {
+		{ .tag  = 'B', .mult = 1       },
+		{ .tag  = 'K', .mult = 1 << 10 },
+		{ .tag  = 'M', .mult = 1 << 20 },
+		{ .tag  = 'G', .mult = 1 << 30 },
+		{ .tag  = 0 },
+	};
+	unsigned long val;
+
+	if (unset) {
+		*s = 0;
+		return 0;
+	}
+
+	val = parse_tag_value(str, tags_size);
+	if (val != (unsigned long) -1) {
+		*s = val;
+		return 0;
+	}
+
+	return -1;
+}
+
 static int record__parse_mmap_pages(const struct option *opt,
 				    const char *str,
 				    int unset __maybe_unused)
@@ -1983,6 +2023,8 @@ static struct option __record_options[] = {
 	OPT_CALLBACK(0, "affinity", &record.opts, "node|cpu",
 		     "Set affinity mask of trace reading thread to NUMA node cpu mask or cpu of processed mmap buffer",
 		     record__parse_affinity),
+	OPT_CALLBACK(0, "max-size", &record.output_max_size,
+		     "size", "Limit the maximum size of the output file", parse_output_max_size),
 	OPT_END()
 };
 
-- 
2.20.1