linux-kernel - Re: [patch 2/2] x86,pat Convert memtype_lock into an rw

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Message-ID: <1269430347.5109.164.camel@twins>
Date:	Wed, 24 Mar 2010 12:32:27 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, "holt@....com" <holt@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [patch 2/2] x86,pat Convert memtype_lock into an rw_lock.

On Wed, 2010-03-17 at 16:19 -0800, Suresh Siddha wrote:
> On Wed, 2010-03-17 at 12:51 -0700, H. Peter Anvin wrote:
> > Well, as you know :) tglx and I are on the road ... I'll try to get to it on Friday before I take off again.
> 
> Also I talked to Thomas about this rwlock conversion and he referred to
> RT issues with rwlock. And the best is to avoid this using RCU.

Its not just RT, even for mainline rwlock_t is a massive pain and often
is no better (actually worse) than a spinlock due to the massive
cacheline bouncing it introduces.


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