linux-kernel - Re: [PATCH 24/24] perf record: Add --buildid-mmap option to enable mmap's build id

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Message-ID: <20201112115710.GE619201@krava>
Date:   Thu, 12 Nov 2020 12:57:10 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Song Liu <songliubraving@...com>,
        Ian Rogers <irogers@...gle.com>,
        Stephane Eranian <eranian@...gle.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 24/24] perf record: Add --buildid-mmap option to enable
 mmap's build id

On Wed, Nov 11, 2020 at 09:00:46AM -0800, Andi Kleen wrote:
> On Mon, Nov 09, 2020 at 10:54:15PM +0100, Jiri Olsa wrote:
> > Adding --buildid-mmap option to enable build id in mmap2 events.
> > It will only work if there's kernel support for that and it disables
> > build id cache (implies --no-buildid).
> 
> What's the point of the option? Why not enable it by default
> if the kernel supports it?
> 
> With the option most user won't get the benefit.
> 
> The only reason I can think of for an option would be to disable
> so that old tools can still process.

yes, that was request in the rfc post, we want the new default
perf.data be still readable by older perf tools

jirka