linux-kernel - Re: RFC: remove __read

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Date:	Thu, 13 Dec 2007 14:44:15 -0800
From:	Harvey Harrison <harvey.harrison@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	bunk@...nel.org, linux-kernel@...r.kernel.org,
	linux-arch <linux-arch@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Subject: Re: RFC: remove __read_mostly

On Thu, 2007-12-13 at 14:32 -0800, David Miller wrote:
> From: Adrian Bunk <bunk@...nel.org>
> Date: Thu, 13 Dec 2007 23:20:44 +0100
> 
> > My question is:
> > Is there anywhere in the kernel a case where __read_mostly brings a 
> > measurable improvement or can it be removed?
> 
> Yes, on SMP when read-mostly objects share cache lines
> with other objects which are frequently written to.
> 
> That is the whole reason we created __read_mostly

I'm curious if anyone has been looking into replacing the __read_mostly
approach with Mathieu's immediate values patchset.  Wouldn't they solve
the cacheline sharing as well (perhaps more eficiently even with trading
some icache for dcache)?

Harvey

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