linux-kernel - Re: 2.6.26: x86/kernel/pci_dma.c: gfp |= __GFP

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Message-ID: <20080525212350.GB8405@one.firstfloor.org>
Date:	Sun, 25 May 2008 23:23:50 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Miquel van Smoorenburg <miquels@...tron.nl>,
	Glauber Costa <gcosta@...hat.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	andi-suse@...stfloor.org
Subject: Re: 2.6.26: x86/kernel/pci_dma.c: gfp |= __GFP_NORETRY ?

On Sun, May 25, 2008 at 08:55:32PM +0100, Alan Cox wrote:
> On Sun, 25 May 2008 18:35:39 +0200
> Andi Kleen <andi@...stfloor.org> wrote:
> 
> > > So how about linux-2.6.26-gfp-no-oom.patch (see previous mail) for
> > > 2.6.26 
> > 
> > Changing the gfp once globally like you did is not right, because
> > the different fallback cases have to be handled differently
> > (see the different cases I discussed in my earlier mail)
> > 
> > Especially the 16MB zone allocation should never trigger the OOM killer.
> 
> That depends how much memory you have.

No it doesn't because the lower zone protection basically never puts
anything that is not GFP_DMA into the 16MB zone.

Just check yourself on your machine using sysrq.

That was one of the motivations behind the mask allocator design.

-Andi
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