linux-kernel - Re: [PATCH v7 04/11] KVM: MMU: zap pages in batch

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Message-ID: <51A2C2DC.6080403@linux.vnet.ibm.com>
Date:	Mon, 27 May 2013 10:20:12 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	gleb@...hat.com, avi.kivity@...il.com, pbonzini@...hat.com,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v7 04/11] KVM: MMU: zap pages in batch

On 05/25/2013 04:34 AM, Marcelo Tosatti wrote:
> On Thu, May 23, 2013 at 03:55:53AM +0800, Xiao Guangrong wrote:
>> Zap at lease 10 pages before releasing mmu-lock to reduce the overload
>> caused by requiring lock
>>
>> After the patch, kvm_zap_obsolete_pages can forward progress anyway,
>> so update the comments
>>
>> [ It improves kernel building 0.6% ~ 1% ]
> 
> Can you please describe the overload in more detail? Under what scenario
> is kernel building improved?

Yes.

The scenario is we do kernel building, meanwhile, repeatedly read PCI rom
every one second.

[
   echo 1 > /sys/bus/pci/devices/0000\:00\:03.0/rom
   cat /sys/bus/pci/devices/0000\:00\:03.0/rom > /dev/null
]

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