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Date: Fri, 9 Aug 2002 09:51:30 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: Daniel Phillips <phillips@arcor.de>
cc: frankeh@watson.ibm.com, <davidm@hpl.hp.com>,
       David Mosberger <davidm@napali.hpl.hp.com>,
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       <Martin.Bligh@us.ibm.com>, <wli@holomorphy.com>,
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Subject: Re: large page patch (fwd) (fwd)
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On Fri, 9 Aug 2002, Daniel Phillips wrote:
> > 
> > Note that even active defrag won't be able to handle the case where you 
> > want have lots of big pages, consituting a large percentage of available 
> > memory.
> 
> Perhaps I'm missing something, but I don't see why.

The statistics are against you. rmap won't help at all with all the other 
kernel allocations, and the dcache/icache is often large, and on big 
machines while there may be tens of thousands of idle entries, there will 
also be hundreds of _non_idle entries that you can't just remove.

> Slab allocations would not have GFP_DEFRAG (I mistakenly wrote GFP_LARGE 
> earlier) and so would be allocated outside ZONE_LARGE.

.. at which poin tyou then get zone balancing problems.

Or we end up with the same kind of special zone that we have _anyway_ in
the current large-page patch, in which case the point of doing this is
what?

		Linus

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