linux-kernel - Re: [PATCH 4/8] KVM: MMU: drop unsync_child

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Message-ID: <4EF3FDB5.90600@linux.vnet.ibm.com>
Date:	Fri, 23 Dec 2011 12:04:05 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 4/8] KVM: MMU: drop unsync_child_bitmap

On 12/18/2011 04:59 PM, Avi Kivity wrote:

> On 12/16/2011 12:16 PM, Xiao Guangrong wrote:
>> unsync_child_bitmap is used to record which spte has unsync page or unsync
>> children, we can set a free bit in the spte instead of it
>>
> 
> unsync_child_bitmap takes one cacheline; the shadow page table takes
> 64.  This will make unsync/resync much more expensive.
> 


Indeed, need more thing about this patch...

> I suggest to put unsync_child_bitmap at the end (together with
> unsync_children) and simply not allocate it when unneeded (have two
> kmem_caches for the two cases).
> 
> 


Good point, thanks Avi.

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