linux-kernel - Re: [PATCH v1 2/5] perf, tools: Save event scaling factors in perf.data

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Date:   Mon, 13 Nov 2017 10:02:37 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     acme@...nel.org, jolsa@...nel.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v1 2/5] perf, tools: Save event scaling factors in
 perf.data

On Thu, Nov 09, 2017 at 06:55:25AM -0800, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> To process metrics, perf script needs to know the scaling
> factors reported by sysfs for events. Save the scaling factors
> in the perf.data metadata in a new SCALE header.
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>

there's event_update event for scale and some other evsel stuff
that was before we were able to put header through pipe

it might be less code changes.. sythesize it via:

       if (has_scale(counter)) {
               err = perf_event__synthesize_event_update_scale(NULL, counter, process_synthesized_event);
               if (err < 0) {
                       pr_err("Couldn't synthesize evsel scale.\n");
                       return err;
               }
       }

and new tool's event_update callback, which is already implemented
in perf_event__process_event_update

having event instead of header feature might have
other drawbacks.. not sure it will fit here

jirka