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

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Message-Id: <20120421100113.4040ac700af6d2b04dda613f@gmail.com>
Date:	Sat, 21 Apr 2012 10:01:13 +0900
From:	Takuya Yoshikawa <takuya.yoshikawa@...il.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	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

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!

> 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.

Thanks,
	Takuya
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