linux-kernel - Re: [PATCH v2 08/15] perf record: write trace data into mmap trace files

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Message-ID: <20201024154423.GG2589351@krava>
Date:   Sat, 24 Oct 2020 17:44:23 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 08/15] perf record: write trace data into mmap trace
 files

On Wed, Oct 21, 2020 at 07:02:56PM +0300, Alexey Budankov wrote:

SNIP

>  
>  	record__synthesize(rec, true);
> -	/* this will be recalculated during process_buildids() */
> -	rec->samples = 0;
>  
>  	if (!err) {
>  		if (!rec->timestamp_filename) {
> @@ -2680,9 +2709,12 @@ int cmd_record(int argc, const char **argv)
>  
>  	}
>  
> -	if (rec->opts.kcore)
> +	if (rec->opts.kcore || record__threads_enabled(rec))
>  		rec->data.is_dir = true;
>  
> +	if (record__threads_enabled(rec))
> +		rec->opts.affinity = PERF_AFFINITY_CPU;

so all the threads will pin to cpu and back before reading?
it makes sense for one thread, but why not pin every thread
at the start?

jirka