linux-kernel - Re: quicklists confuse meminfo

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Date:	Mon, 10 Mar 2008 17:19:32 +0000 (GMT)
From:	Hugh Dickins <hugh@...itas.com>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Christoph Lameter <clameter@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Bart Van Assche <bart.vanassche@...il.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: quicklists confuse meminfo

On Mon, 10 Mar 2008, Andi Kleen wrote:
> Christoph Lameter <clameter@....com> writes:
> > 
> > Zeroed pages however will not address the issue of having initialized pgd 
> > (which seems to be what i386 needs).
> 
> pgd is tiny on i386 PAE (4 * 16 bytes). Are you sure reinitializing that
> is a serious issue? ...

It used to be tiny (32 aligned bytes), then 2.6.22's quicklist enlarged
that to a whole (lowmem) page.  I think we were all too busy with other
stuff to protest loudly enough about that bloat.

If the quicklists are going, it'd be good for PAE to go back to a
kmem_cache of 32-byte entries as in 2.6.21 - I think Ingo's patch is
still using a whole page there.

Or have sl?b alignment changes, or virtualization issues (locking
per underlying struct page?), made a kmem_cache awkward there now?

Hugh
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