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Subject[PATCH v3] perf record: Add support for limit perf output file size
Date
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@windriver.com>
---
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
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