linux-kernel - Re: [PATCH] ksm: set anon_vma of first rmap_item of ksm page to page's anon_vma other than vma's anon

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Message-Id: <20160623164931.da352f7e6f4b115aba13f37e@linux-foundation.org>
Date:	Thu, 23 Jun 2016 16:49:31 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	<zhouxianrong@...wei.com>
Cc:	<linux-mm@...ck.org>, <hughd@...gle.com>, <aarcange@...hat.com>,
	<kirill.shutemov@...ux.intel.com>, <dave.hansen@...ux.intel.com>,
	<zhouchengming1@...wei.com>, <geliangtang@....com>,
	<linux-kernel@...r.kernel.org>, <zhouxiyu@...wei.com>,
	<wanghaijun5@...wei.com>
Subject: Re: [PATCH] ksm: set anon_vma of first rmap_item of ksm page to
 page's anon_vma other than vma's anon_vma

On Thu, 23 Jun 2016 21:33:54 +0800 <zhouxianrong@...wei.com> wrote:

> From: z00281421 <z00281421@...esmail.huawei.com>
> 
> set anon_vma of first rmap_item of ksm page to page's anon_vma
> other than vma's anon_vma so that we can lookup all the forked
> vma of kpage via reserve map. thus we can try_to_unmap ksm page
> completely and reclaim or migrate the ksm page successfully and
> need not to merg other forked vma addresses of ksm page with
> building a rmap_item for it ever after.
> 
> a forked more mapcount ksm page with partially merged vma addresses and
> a ksm page mapped into non-VM_MERGEABLE vma due to setting MADV_MERGEABLE
> on one of the forked vma can be unmapped completely by try_to_unmap.
> 

hm, OK, so this is an efficiency increase rather than a functional
change?

If so, are you able to quantify the benefit?  ie, how much faster did
things get?

I'll queue it up and shall await Hugh review (please).