linux-kernel - Re: [PATCH v5 0/9] KVM: fast page fault

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Message-ID: <4FBDE0FB.3040100@redhat.com>
Date:	Thu, 24 May 2012 10:19:23 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v5 0/9] KVM: fast page fault

On 05/24/2012 09:31 AM, Xiao Guangrong wrote:
> On 05/23/2012 07:37 PM, Avi Kivity wrote:
> 
>> On 05/23/2012 11:51 AM, Xiao Guangrong wrote:
>>> Changlog:
>>> This are some changes from Marcelo's review:
>>> - drop SPTE_WRITE_PROTECT bit, now, only one bit is needed to do
>>>   lockless update.
>>>
>>> - always atomicly update spte if it can be updated out of mmu-lock.
>>>
>>> - flod the judgement of tlb flush into mmu_spte_update(), make the
>>>   code easilyer audited.
>>>
>>> Performance result:
>>> - autoest migration test (smp2.Fedora.16.64.migrate.with_autotest.dbench.unix):
>>>                                                    before     after
>>> smp2.Fedora.16.64.migrate.unix                        93      91    +2.1%
>>> smp2.Fedora.16.64.migrate.with_autotest.dbench.unix   218     188   +13.7%
>>>
>>> - the benchmark attached is used to measure the resuming time
>>>   after dirty-log
>>>                             before            after
>>> Run 10 times, Avg time:   512466818 ns.      269231261 ns   +47.5%
>> 
>> Still scary (esp. indirect sptes), but looks pretty good.
> 
> 
> Hmm, i do not have a better way to solve the ABA problem on indirect spte now. :(
> How about only allow fast page fault to work for direct spte?
> 

I'll certainly be more comfortable with that, at least to start with.

-- 
error compiling committee.c: too many arguments to function
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