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

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Date:	Tue, 17 Apr 2012 23:47:31 +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

On Mon, 16 Apr 2012 11:36:25 +0800
Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com> wrote:

> I tested it with kernbench, no regression is found.

Because kernbench is not at all good test for this.

> It is not a problem since the iter and spte should be in the cache.

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.

This is not a pure cleanup and introduces significant regression to
rmap handling.

This is the reason why I asked to remove "cleanup patches" from this
patch series.  Had it been really trivial cleanup, I would not have
asked that.

Note: if you had checked the worst case latency with this patch series,
you should have noticed this regression by yourself.

Auto-test and kernbench are not enough to see the effect of this work.

Thanks,
	Takuya
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