linux-kernel - Re: [PATCH v8 8/8] x86/tlb: do flush_tlb_kernel

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Message-ID: <4FD93DC7.8020501@intel.com>
Date:	Thu, 14 Jun 2012 09:26:31 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Andi Kleen <ak@...ux.intel.com>, linux-tegra@...r.kernel.org,
	linux-omap@...r.kernel.org
CC:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, arnd@...db.de,
	rostedt@...dmis.org, fweisbec@...il.com, jeremy@...p.org,
	seto.hidetoshi@...fujitsu.com, borislav.petkov@....com,
	tony.luck@...el.com, luto@....edu, riel@...hat.com, avi@...hat.com,
	len.brown@...el.com, tj@...nel.org, akpm@...ux-foundation.org,
	cl@...two.org, jbeulich@...e.com, eric.dumazet@...il.com,
	akinobu.mita@...il.com, cpw@....com, penberg@...nel.org,
	steiner@....com, viro@...iv.linux.org.uk,
	kamezawa.hiroyu@...fujitsu.com, aarcange@...hat.com,
	rientjes@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 8/8] x86/tlb: do flush_tlb_kernel_range by 'invlpg'

On 06/14/2012 09:10 AM, Alex Shi wrote:

> On 06/13/2012 10:56 PM, Andi Kleen wrote:
> 
>> On Tue, Jun 12, 2012 at 05:06:45PM +0800, Alex Shi wrote:
>>> This patch do flush_tlb_kernel_range by 'invlpg'. The performance pay
>>> and gain was analysed in my patch (x86/flush_tlb: try flush_tlb_single
>>> one by one in flush_tlb_range). Now we move this logical into kernel
>>> part. The pay is multiple 'invlpg' execution cost, that is same. but
>>>  the gain(cost reducing of TLB entries refilling) is absolutely
>>> increased.
>>
>> The subtle point is whether INVLPG flushes global pages or not.
>> After some digging I found a sentence in the SDM that says it does.
>> So it may be safe.
> 
> 
> Many thanks for your time!
> 
>>
>> What does it improve?
> 
> 
> I have not specific benchmark for this. partly due to the gain theory
> was proved since it is same as previous user process's page table flush.
> 
> The user of tlb kernel flush in kernel is vmalloc. and Android binder
> IPC subsystem is using it(drivers/staging/android/binder.c)
> 
> I am wondering if it can help Andriod on this?
> So, add cc to android-kernel@...glegroups.com


Sorry, Andriod reject posting without register, so cc to
linux-omap@...r.kernel.org and linux-tegra@...r.kernel.org instead.

> 
>> -Andi
> 
> 


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