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

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Date:   Mon, 21 Oct 2019 15:41:37 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jiwei Sun <jiwei.sun@...driver.com>
Cc:     acme@...hat.com, arnaldo.melo@...il.com,
        linux-kernel@...r.kernel.org, alexander.shishkin@...ux.intel.com,
        mpetlan@...hat.com, namhyung@...nel.org, a.p.zijlstra@...llo.nl,
        adrian.hunter@...el.com, Richard.Danter@...driver.com
Subject: Re: [PATCH v4] perf record: Add support for limit perf output file
 size

On Wed, Sep 25, 2019 at 03:06:37PM +0800, Jiwei Sun wrote:

SNIP

>  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");

I think the message whouldn't be a warning, the user asked for
that, maybe something more like:

  [ perf record: perf size limit reached (XXMB), stopping session ]

> +		raise(SIGTERM);

could we just set 'done = 1' what's the benefit in killing perf?

thanks,
jirka