linux-kernel - Re: [PATCH v2 2/4] perf record: implement -z=<level> and --mmap-flush=<thres> options

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Date:   Tue, 12 Feb 2019 14:09:46 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] perf record: implement -z=<level> and
 --mmap-flush=<thres> options

On Mon, Feb 11, 2019 at 11:22:38PM +0300, Alexey Budankov wrote:

SNIP

> @@ -1147,6 +1193,10 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>  	fd = perf_data__fd(data);
>  	rec->session = session;
>  
> +	rec->opts.comp_level = 0;
> +	session->header.env.comp_level = rec->opts.comp_level;
> +	session->header.env.comp_type = PERF_COMP_NONE;
> +
>  	record__init_features(rec);
>  
>  	if (rec->opts.use_clockid && rec->opts.clockid_res_ns)
> @@ -1176,6 +1226,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>  		err = -1;
>  		goto out_child;
>  	}
> +	session->header.env.comp_mmap_len = session->evlist->mmap_len;

so the comp_mmap_len is the max length of the compressed packet?

any idea if this value might have some impact on the processing speed?

I see you mentioned the size reduction, could you also meassure
the record overhead?

thanks,
jirka