linux-kernel - Re: [patch] x86, tlb: switch cr3 in leave

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Message-ID: <4F70F217.4060005@zytor.com>
Date:	Mon, 26 Mar 2012 15:47:51 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch] x86, tlb: switch cr3 in leave_mm() only when needed

On 03/26/2012 03:47 PM, Suresh Siddha wrote:
> On Fri, 2012-03-23 at 09:37 +0100, Ingo Molnar wrote:
>> * Suresh Siddha <suresh.b.siddha@...el.com> wrote:
>>
>>> I was reviewing this code in some other context and thought 
>>> this optimization makes sense. Unless someone beats me, I can 
>>> collect some data on Monday.
>>
>> Would be really nice to get this data.
>>
> 
> On an idle system with 32logical cpu's (2 socket/8-core each) the
> original kernel did the unnecessary load_cr3 2988 times during an
> interval of 5 seconds.
> 
> With the fix, that count drops to 9 times.
> 

Nice.

	-hpa

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