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From: Linus Torvalds <torvalds@transmeta.com>
To: Andrew Morton <akpm@digeo.com>
Cc: Ingo Molnar <mingo@elte.hu>,
	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 15:56:29 -0700 (PDT)	[thread overview]
Message-ID: <Pine.LNX.4.33.0209261550590.1573-100000@penguin.transmeta.com> (raw)
In-Reply-To: <Pine.LNX.4.33.0209261533230.1345-100000@penguin.transmeta.com>


On Thu, 26 Sep 2002, Linus Torvalds wrote:
> 
> and then when we pin a page, we do
> 
> 	/* This is part of the 
> 	struct page_change_struct pinned_data;

That "This is part of the " comment should continue with "struct futex_q", 
but I went off and was supposed to check what the futex data structure was 
called, and forgot about updating it.

Anyway, the point being that this needs no new allocations in _any_ path,
and only extends a structure that we already need for the slow case for
futexes. It does imply a new lock, though, and the COW path would have to
check that hash (which should scale pretty well, since we only have
entries here when somebody is blocked on a futex).

Oh, and we need a new hash table, since the native futex hash can't just
be re-used due to different indexing - the futex hash is based on physical
page and offset, while the page_change_struct hash is based on virtual
address and the mm.

(I initially thought we could make the page_change_struct hash be based on 
physical page, but there can be multiple instances of the same physical 
page being mapped into the same VM, so that wouldn't be a good thing - 
we'd get callbacks for the wrong virtual address being COW'ed).

		Linus


  reply	other threads:[~2002-09-26 22:48 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-09-26 11:30 Ingo Molnar
2002-09-26 15:01 ` Linus Torvalds
2002-09-26 22:09 ` Andrew Morton
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 [this message]
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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