Subject: Re: objrmap-core-1 (rmap removal for file mappings to avoid 4:4 in
	<=16G machines)
From: Arjan van de Ven <arjanv@redhat.com>
Reply-To: arjanv@redhat.com
To: Andrea Arcangeli <andrea@suse.de>
Cc: Linus Torvalds <torvalds@osdl.org>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org
In-Reply-To: <20040308202433.GA12612@dualathlon.random>
References: <20040308202433.GA12612@dualathlon.random>
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Organization: Red Hat, Inc.
Message-Id: <1078781318.4678.9.camel@laptop.fenrus.com>
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Date: Mon, 08 Mar 2004 22:28:38 +0100
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> . Basically without
> this fix it's like 2.6 is running w/o pte-highmem. 700 tasks with 2.7G
> of shm mapped each would run the box out of zone-normal even with 4:4.
> With 3:1 100 tasks would be enough. Math is easy:
>=20
> 	2.7*1024*1024*1024/4096*8*100/1024/1024/1024
> 	2.7*1024*1024*1024/4096*8*700/1024/1024/1024


not saying your patch is not useful or anything,but there is a less
invasive shortcut possible. Oracle wants to mlock() its shared area, and
for mlock()'d pages we don't need a pte chain *at all*. So we could get
rid of a lot of this overhead that way.

Now your patch might well be useful for a lot of other reasons too, but
if this is the only one there are potential less invasive solutions for
2.6.


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