linux-kernel - Re: [RFC PATCH 1/1] prefetch result in 64 bit atomic ops

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Message-ID: <20140415075220.GC17408@arm.com>
Date:	Tue, 15 Apr 2014 08:52:20 +0100
From:	Will Deacon <will.deacon@....com>
To:	Pranith Kumar <bobby.prani@...il.com>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	Joe Perches <joe@...ches.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 1/1] prefetch result in 64 bit atomic ops

Hi Pranith,

On Mon, Apr 14, 2014 at 07:45:22PM +0100, Pranith Kumar wrote:
> Please disregard previous patches. This is the correct one. 
> 
> prefetch destination as is being done in ARM32 atomic ops

Whilst this looks like a potentially sensible optimisation (based on the
results I saw on AArch32), I don't think we can take this patch without some
benchmarks on real silicon. The interaction between the half-barrier atomic
instructions and prfm isn't immediately obvious to me, and we should also
consider looking at streaming preload vs the l1keep option.

Did you write this patch as a basic port of the arch/arm/ patches I wrote,
or was it based on performance figures from real hardware?

Will
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