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From: Andrew Morton <akpm@digeo.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@transmeta.com>,
	Rusty Russell <rusty@rustcorp.com.au>,
	linux-kernel@vger.kernel.org
Subject: Re: [patch] 'sticky pages' support in the VM, futex-2.5.38-C5
Date: Thu, 26 Sep 2002 15:09:12 -0700	[thread overview]
Message-ID: <3D938588.4508FDF@digeo.com> (raw)
In-Reply-To: Pine.LNX.4.44.0209261311070.11487-100000@localhost.localdomain

Ingo Molnar wrote:
> 
> ...
> another implementation would be an idea from Linus: the page's lru list
> pointer can in theory be used for pinned pages (pinned pages do not have
> much LRU meaning anyway), and this pointer could specify the 'owner' MM of
> the physical page. The COW fault handler then checks the sticky page:

Overloading page->lru in this way is tricky.   If we can guarantee
that the page is anonymous (anonymise it if it's file-backed, pull
it out of swapcache) then fine, ->mapping, ->list.next, ->list.prev,
->index and ->private are available.

Can we do that?

>  - if the faulting context is a non-owner (ie. the fork()-ed child), then
>    the normal COW path is taken - new page allocated and installed.
> 
>  - if the faulting context is the owner, then the pte chain is walked, and
>    the new page is installed into every 'other' pte. This needs a
>    cross-CPU single-page TLB flush though. The TLB flush could be
>    optimized if we had a way to get to the mapping MM's of the individual
>    pte chain entries - is this possible?

Going from a pte back up to the owning MM is possible, yes.  See
mm/rmap.c:try_to_unmap_one().  The caller would have to hold the
page's rmap_lock.

  parent reply	other threads:[~2002-09-26 22:04 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-09-26 11:30 [patch] 'sticky pages' support in the VM, futex-2.5.38-C5 Ingo Molnar
2002-09-26 15:01 ` Linus Torvalds
2002-09-26 22:09 ` Andrew Morton [this message]
2002-09-26 22:32   ` Linus Torvalds
2002-09-27  7:53     ` Ingo Molnar
2002-09-26 22:45   ` Linus Torvalds
2002-09-26 22:56     ` Linus Torvalds
2002-09-27 11:11     ` Ingo Molnar
2002-10-04 22:47 ` Jamie Lokier
2002-10-04 23:20   ` Linus Torvalds
     [not found] <200209261501.g8QF1pc02251@penguin.transmeta.com>
2002-09-26 15:27 ` Ingo Molnar
2002-09-26 16:48   ` Alan Cox
2002-09-27  8:05 Martin Wirth
2002-09-27  9:27 ` Ingo Molnar

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