linux-kernel - Re: [PATCH v2 07/16] KVM: MMU: introduce for_each_pte_list

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Date:	Sat, 21 Apr 2012 12:36:21 +0800
From:	Xiao Guangrong <xiaoguangrong.eric@...il.com>
To:	Takuya Yoshikawa <takuya.yoshikawa@...il.com>
CC:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
	Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 07/16] KVM: MMU: introduce for_each_pte_list_spte

On 04/21/2012 09:01 AM, Takuya Yoshikawa wrote:

> Sorry for the delay.
> 
> On Wed, 18 Apr 2012 12:01:03 +0800
> Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com> wrote:
> 
>>> I have checked dirty-log-perf myself with this patch [01-07].
>>>
>>> GET_DIRTY_LOG for 1GB dirty pages has become more than 15% slower.
> 
>> Thanks for your test!
>>
>> Unbelievable, i will do more test and check it more carefully.
> 
> GET_DIRTY_LOG now traverses rmap lists intensively.
> So only a small change can affect the performance when there are many
> dirty pages.
> 
>> Could you please open your tool, then i can reproduction it and find the
>> real reason?
> 
> It's already in kvm unit tests!
> 


Great, i will check that.

>> I will check whether your tool is better then kernbench/autotest after
>> review your tool.
> 
> Let's focus on "lock-less" now: so dirty-log-perf is not needed now.
> 
> I think you failed to appeal the real advantage of your "lock-less" approach!
> I will write about this on v3-threads.


Thank you very much, Takuya!
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