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Date: Wed, 19 Dec 2007 11:36:00 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Ingo Molnar <mingo@elte.hu>
CC: Venki Pallipadi <venkatesh.pallipadi@intel.com>,
       Thomas Gleixner <tglx@linutronix.de>, Len Brown <lenb@kernel.org>,
       linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86: Voluntary leave_mm before entering ACPI C3
References: <20071219183443.GA547@linux-os.sc.intel.com> <20071219193255.GA2158@elte.hu>
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Ingo Molnar wrote:
> * Venki Pallipadi <venkatesh.pallipadi@intel.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