linux-kernel - Re: [PATCH RFC] x86: enforce inlining for atomics

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Message-ID: <CAPh34mfe9FDLZ+cFBJQB1B8rBMwU_SpFHpp9nsH=a1jW=gN9+g@mail.gmail.com>
Date:	Tue, 21 Apr 2015 00:08:46 +0200
From:	Hagen Paul Pfeifer <hagen@...u.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH RFC] x86: enforce inlining for atomics

On 20 April 2015 at 23:56, Borislav Petkov <bp@...en8.de> wrote:

> Hmm, that must be config-specific as doing
>
> objdump -D vmlinux | grep -i "atomic_add"
>
> here gives me only "drm_atomic_add_affected_connectors" matches.
>
> It probably gets inlined here always...

Probably, the config is allyesconfig minus trace/kernel adress
sanitizer and gcov related options.

> Other than that, this patch should actually even show some speedup as
> we're getting rid of the stack preparation and function call overhead.
> Have you done any benchmarks with it?

No, but I am sure that a benchmark should show at least theoretically
better perf numbers. But the numbers should be the measurement
uncertainty range. The avoided cache line miss should be the greatest
perf effect.

Hagen
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