[PATCH v5] perf record: Add support for limit perf output file size

[jsun4]

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.

In order to make the perf.data parsable, we just limit the sample data
size, since the perf.data consists of many headers and sample data and
other data, the actual size of the recorded file will bigger than the
setting value.

Testing it:

 # ./perf record -a -g --max-size=10M
 Couldn't synthesize bpf events.
 [ perf record: perf size limit reached (10249 KB), stopping session ]
 [ perf record: Woken up 32 times to write data ]
 [ perf record: Captured and wrote 10.133 MB perf.data (71964 samples) ]

 # ls -lh perf.data
 -rw------- 1 root root 11M Oct 22 14:32 perf.data

 # ./perf record -a -g --max-size=10K
 [ perf record: perf size limit reached (10 KB), stopping session ]
 Couldn't synthesize bpf events.
 [ perf record: Woken up 0 times to write data ]
 [ perf record: Captured and wrote 1.546 MB perf.data (69 samples) ]

 # ls -l perf.data
 -rw------- 1 root root 1626952 Oct 22 14:36 perf.data

Signed-off-by: Jiwei Sun <jiwei.sun@xxxxxxxxxxxxx>
---
v5 changes:
  - Change the output format like [ perf record: perf size limit XX ]
  - change the killing perf way from "raise(SIGTERM)" to set "done == 1"

v4 changes:
  - Just show one WARNING message after reached the limit.

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 |  4 +++
 tools/perf/builtin-record.c              | 46 +++++++++++++++++++++++-
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 8a4506113d9f..ebcba1f95513 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -574,6 +574,10 @@ Implies --tail-synthesize.
 --kcore::
 Make a copy of /proc/kcore and place it into a directory with the perf data file.
 
+--max-size=<size>::
+Limit the sample data max size, <size> is expected to be a number with
+appended unit character - B/K/M/G
+
 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 f6664bb08b26..b9ddfcda9611 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -94,8 +94,11 @@ 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 done;
+
 static volatile int auxtrace_record__snapshot_started;
 static DEFINE_TRIGGER(auxtrace_snapshot_trigger);
 static DEFINE_TRIGGER(switch_output_trigger);
@@ -123,6 +126,12 @@ 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 mmap *map __maybe_unused,
 			 void *bf, size_t size)
 {
@@ -135,6 +144,13 @@ static int record__write(struct record *rec, struct mmap *map __maybe_unused,
 
 	rec->bytes_written += size;
 
+	if (record__output_max_size_exceeded(rec) && !done) {
+		fprintf(stderr, "[ perf record: perf size limit reached (%lu KB),"
+				" stopping session ]\n",
+				rec->bytes_written >> 10);
+		done = 1;
+	}
+
 	if (switch_output_size(rec))
 		trigger_hit(&switch_output_trigger);
 
@@ -499,7 +515,6 @@ static int record__pushfn(struct mmap *map, void *to, void *bf, size_t size)
 	return record__write(rec, map, bf, size);
 }
 
-static volatile int done;
 static volatile int signr = -1;
 static volatile int child_finished;
 
@@ -1984,6 +1999,33 @@ 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)
@@ -2311,6 +2353,8 @@ static struct option __record_options[] = {
 			    "n", "Compressed records using specified level (default: 1 - fastest compression, 22 - greatest compression)",
 			    record__parse_comp_level),
 #endif
+	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