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

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Message-ID: <1332802025.12381.2.camel@sbsiddha-desk.sc.intel.com>
Date:	Mon, 26 Mar 2012 15:47:05 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, 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 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.

thanks,
suresh

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