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

[Arnaldo Carvalho de Melo]

Em Mon, Mar 11, 2019 at 03:12:33PM +0800, Jiwei Sun escreveu:
> 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!

why so many messages? I tried with --max-size 50K and got way more
messages, please find why this is taking place and try show just one
message and finish the command as soon as the max size is reached.

- Arnaldo

>   [ 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

-- 

- Arnaldo