Re: [PATCH v4] perf record: Add support for limit perf output file size

[Jiwei Sun]

Hello Arnaldo & Jirka,

Do you have any other suggestions regarding the patch? 
Any suggestions are welcome. Thank you very much.

Regards,
Jiwei

On 2019e9409f25f% 15:06, Jiwei Sun wrote:
> 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.
> WARNING: The perf data has already reached the limit, stop recording!
> [ perf record: Woken up 30 times to write data ]
> [ perf record: Captured and wrote 10.233 MB perf.data (175650 samples) ]
> Terminated
> 
>  # ls -lh perf.data
> -rw------- 1 root root 11M Jul 17 14:01 perf.data
> 
>  # ./perf record -a -g --max-size=10K
> WARNING: The perf data has already reached the limit, stop recording!
> Couldn't synthesize bpf events.
> [ perf record: Woken up 0 times to write data ]
> [ perf record: Captured and wrote 1.824 MB perf.data (67 samples) ]
> Terminated
> 
>  # ls -lh perf.data
> -rw------- 1 root root 1.9M Jul 17 14:05 perf.data
> 
> Signed-off-by: Jiwei Sun <jiwei.sun@xxxxxxxxxxxxx>
> ---
> 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              | 42 ++++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index c6f9f31b6039..f1c6113fbc82 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -571,6 +571,10 @@ config terms. For example: 'cycles/overwrite/' and 'instructions/no-overwrite/'.
>  
>  Implies --tail-synthesize.
>  
> +--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 48600c90cc7e..30904d2a3407 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -91,6 +91,7 @@ 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;
> @@ -120,6 +121,12 @@ 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)
>  {
> @@ -132,6 +139,12 @@ static int record__write(struct record *rec, struct mmap *map __maybe_unused,
>  
>  	rec->bytes_written += size;
>  
> +	if (record__output_max_size_exceeded(rec)) {
> +		WARN_ONCE(1, "WARNING: The perf data has already reached "
> +			     "the limit, stop recording!\n");
> +		raise(SIGTERM);
> +	}
> +
>  	if (switch_output_size(rec))
>  		trigger_hit(&switch_output_trigger);
>  
> @@ -1936,6 +1949,33 @@ 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)
> @@ -2262,6 +2302,8 @@ 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()
>  };
>  
>