linux-kernel - Re: [PATCH v5 17/17] x86/perf, static_call: Optimize x86

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Date:   Thu, 9 Jul 2020 13:16:34 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, rostedt@...dmis.org,
        mhiramat@...nel.org, bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, jpoimboe@...hat.com,
        pbonzini@...hat.com, mathieu.desnoyers@...icios.com,
        linux@...musvillemoes.dk
Subject: Re: [PATCH v5 17/17] x86/perf, static_call: Optimize x86_pmu methods

On Wed, Jun 24, 2020 at 05:30:41PM +0200, Peter Zijlstra wrote:
> Replace many of the indirect calls with static_call().
> 
> XXX run performance numbers

So I finally got around to doing that, and the average PMI time, as
measured by perf_sample_event_took()*:

PRE:	3283.03 [ns]
POST:	3145.12 [ns]

Which is a ~138 [ns] win per PMI, or ~4.2% decrease.

[*] on my IVB-EP, using: 'perf record -a -e cycles -- make O=defconfig-build/ -j80'