linux-kernel - Re: [PATCH 2/6] perf tools: Store clock references for -k/--clockid option

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Date:   Mon, 3 Aug 2020 13:35:59 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        David Ahern <dsahern@...il.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Michael Petlan <mpetlan@...hat.com>,
        Ian Rogers <irogers@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Geneviève Bastien <gbastien@...satic.net>,
        Wang Nan <wangnan0@...wei.com>,
        Jeremie Galarneau <jgalar@...icios.com>
Subject: Re: [PATCH 2/6] perf tools: Store clock references for -k/--clockid
 option

On Mon, Aug 03, 2020 at 12:55:50PM +0900, Namhyung Kim wrote:

SNIP

> > diff --git a/tools/perf/Documentation/perf.data-file-format.txt b/tools/perf/Documentation/perf.data-file-format.txt
> > index b6472e463284..c484e81987c7 100644
> > --- a/tools/perf/Documentation/perf.data-file-format.txt
> > +++ b/tools/perf/Documentation/perf.data-file-format.txt
> > @@ -389,6 +389,19 @@ struct {
> >  Example:
> >   cpu pmu capabilities: branches=32, max_precise=3, pmu_name=icelake
> >  
> > +	HEADER_CLOCK_DATA = 29,
> > +
> > +	Contains clock id and its reference time together with wall clock
> > +	time taken at the 'same time', both values are in nanoseconds.
> > +	The format of data is as below.
> > +
> > +struct {
> > +	u32 version;  /* version = 1 */
> > +	u32 clockid;
> > +	u64 clockid_time_ns;
> > +	u64 wall_clock_ns;
> > +};
> > +
> 
> It seems that it's slightly different than what it actually write to a file.
> Specifically the last two fields should be reversed IMHO.

oops, you're right.. wil fix in new version

> 
> 
> >  	other bits are reserved and should ignored for now
> >  	HEADER_FEAT_BITS	= 256,
> >
> [SNIP]
> 
> > diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h
> > index 1ab2682d5d2b..4098a63d5e64 100644
> > --- a/tools/perf/util/env.h
> > +++ b/tools/perf/util/env.h
> > @@ -100,6 +100,18 @@ struct perf_env {
> >  	/* For fast cpu to numa node lookup via perf_env__numa_node */
> >  	int			*numa_map;
> >  	int			 nr_numa_map;
> > +
> > +	/* For real clock time refference. */
> 
> typo: reference

ok

SNIP

> > +	else {
> > +		strftime(date, sizeof(date), "%F %T", &ltime);
> > +		scnprintf(tstr, sizeof(tstr), "%s.%06d",
> > +			  date, (int) tod_ns.tv_usec);
> > +	}
> > +
> > +	fprintf(fp, "# clockid: %s (%u)\n", clockid_name(clockid), clockid);
> > +	fprintf(fp, "# reference time: %s = %ld.%06d (TOD) = %ld.%ld (%s)\n",
> 
> Shouldn't the last one be %ld.%09ld?

sure, why not

thanks,
jirka