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From: Daniel Phillips <phillips@bonn-fries.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [RFC] Arch option to touch newly allocated pages
Date: Thu, 7 Mar 2002 18:54:05 +0100
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Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), yodaiken@fsmlabs.com,
        jdike@karaya.com (Jeff Dike), bcrl@redhat.com (Benjamin LaHaise),
        hpa@zytor.com (H. Peter Anvin), linux-kernel@vger.kernel.org
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On March 7, 2002 05:19 pm, Alan Cox wrote:
> > Higher order allocation - imho we can fix that too, eventually, however it's a lot
> > more work.  First we have to have reliable physical defragmentation.
> > 
> > > And if we are OOM - we want to return NULL
> > 
> > What good does that do?
> 
> It allows us to continue. It avoids the deadlocks.

Could you describe the deadlock, please?

> It lets the caller make an intelligent decision.

I maintain it's the wrong interface, we're mixing two concepts together there:

  - VM can't find blocks that are freeable, so fails and dumps the problem
    on the caller, which has to busy wait.  This sucks.

  - The VM is under heavy load and the caller doesn't really need the memory
    that badly because it has a fallback, the VM somehow knows this, so fails
    the allocation and everybody is happy.

These should be separated, and we should fix the former.

-- 
Daniel
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