linux-kernel - Re: [PATCH] x86: Voluntary leave

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Message-ID: <476972A0.3050105@zytor.com>
Date:	Wed, 19 Dec 2007 11:36:00 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Venki Pallipadi <venkatesh.pallipadi@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Len Brown <lenb@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: Voluntary leave_mm before entering ACPI C3

Ingo Molnar wrote:
> * Venki Pallipadi <venkatesh.pallipadi@...el.com> wrote:
> 
>> Aviod TLB flush IPIs during C3 states by voluntary leave_mm() before 
>> entering C3.
>>
>> The performance impact of TLB flush on C3 should not be significant 
>> with respect to C3 wakeup latency. Also, CPUs tend to flush TLB in 
>> hardware while in C3 anyways.
>>

Are there any CPUs around which *don't* flush the TLB across C3?  (I 
guess it's not guaranteed by the spec, though, and as TLBs grow larger 
there might be incentive to keep them online.)

	-hpa
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