linux-kernel - Re: [PATCH 1/1] mm: add dirty

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Message-ID: <20071127013028.GA31038@brong.net>
Date:	Tue, 27 Nov 2007 12:30:28 +1100
From:	Bron Gondwana <brong@...tmail.fm>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Bron Gondwana <brong@...tmail.fm>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christian Kujau <lists@...dbynature.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	robm@...tmail.fm
Subject: Re: [PATCH 1/1] mm: add dirty_highmem option

On Mon, Nov 26, 2007 at 09:53:17AM -0800, Linus Torvalds wrote:
> 
> 
> On Thu, 22 Nov 2007, Bron Gondwana wrote:
> > 
> > This patch includes some code cleanup from Linus and a toggle in
> > /proc/sys/vm/dirty_highmem which can be set to 1 to add the highmem
> > back to the total available memory count.
> 
> Just to verify - can you confirm that this "just fixes it" for you?
> 
> I think this is the right approach to take, and seems very safe (ie people 
> who know that their loads are ok can just set the flag), but I do want to 
> verify that there was nothing else going on, and that you now see the same 
> performance as you did in 2.6.16?
> 
> The other alternative, of course, would be to simply allow the dirty 
> percentages to be > 100%, but that's just *odd* ;)

Yes, toggling dirty_highmem "just fixes it" in all our tests.  I hadn't
tested it on the production machine yet - but I'm just installing it
there now since it's been running fine on a less important machine for
a few days now.

I did wonder about allowing the dirty percentage to go way up, but that
would have cause "this one goes up to 110%" comments in the sysctl
limits code and people would have thought I was childish.  Can't have
that.  Much better to have "int one = 1" instead.

Bron.
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