linux-kernel - Re: [PATCH 00/13] KVM: MMU: fast page fault

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Message-Id: <20120417213748.f3c4ae8d0056676fd33a47c5@gmail.com>
Date:	Tue, 17 Apr 2012 21:37:48 +0900
From:	Takuya Yoshikawa <takuya.yoshikawa@...il.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
	kvm-ppc@...r.kernel.org, Marcelo Tosatti <mtosatti@...hat.com>,
	Xiao Guangrong <xiaoguangrong.eric@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 00/13] KVM: MMU: fast page fault

On Tue, 17 Apr 2012 10:51:40 +0300
Avi Kivity <avi@...hat.com> wrote:

> That's true with the write protect everything approach we use now.  But
> it's not true with range-based write protection, where you issue
> GET_DIRTY_LOG on a range of pages and only need to re-write-protect them.
> 
> (the motivation for that is to decrease the time between GET_DIRTY_LOG
> and sending the page; as the time increases, the chances that the page
> got re-dirtied go up).

Thank you for explaining this.

I was planning to give the userspace more freedom.

Since there are many known algorithms to predict hot memory pages,
the userspace will be able to tune the frequency of GET_DIRTY_LOG for such
parts not to get too many faults repeatedly, if we can restrict the range
of pages to protect.

This is the fine-grained control.

Thanks,
	Takuya
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