ZERO PAGE again v3. [LWN.net]

From:		KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To:		linux-mm@kvack.org
Subject:		[PATCH 0/2] ZERO PAGE again v3.
Date:		Thu, 9 Jul 2009 12:24:28 +0900
Message-ID:		<20090709122428.8c2d4232.kamezawa.hiroyu@jp.fujitsu.com>
Cc:		"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, npiggin@suse.de, "hugh.dickins@tiscali.co.uk" <hugh.dickins@tiscali.co.uk>, avi@redhat.com, "akpm@linux-foundation.org" <akpm@linux-foundation.org>, torvalds@linux-foundation.org, aarcange@redhat.com
Archive-link:		Article, Thread

After v2 discussion, I felt that "Go" sign can be given if implemetaion is neat
and tiny and overhead seems very small. Here is v3.

In this version,

 - use pte_special() in vm_normal_page()
   All ZERO_PAGE check will go down to vm_normal_page() and check is done here.
   Some new flags in follow_page() and get_user_pages().

 - per arch use-zero-page config is added.
   IIUC, archs which have _PAGE_SPECIAL is only x86, powerpc, s390.
   Because this patch make use of pte_special() check, config to use zero page
   is added and you can turn it off if necessary.
   I this patch, only x86 is turned on which I can test.

Any comments are welcome. 

Thanks,
-Kame

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