linux-kernel - Re: [QUICKLIST 0/4] Arch independent quicklists V2

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Date:	Tue, 13 Mar 2007 19:03:38 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Christoph Lameter <clameter@....com>, linux-mm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [QUICKLIST 0/4] Arch independent quicklists V2

Andrew Morton wrote:
>>On Tue, 13 Mar 2007 00:13:25 -0700 (PDT) Christoph Lameter <clameter@....com> wrote:
>>Page table pages have the characteristics that they are typically zero
>>or in a known state when they are freed.
> 
> 
> Well if they're zero then perhaps they should be released to the page allocator
> to satisfy the next __GFP_ZERO request.  If that request is for a pagetable
> page, we break even (except we get to remove special-case code).  If that
> __GFP_ZERO allocation was or some application other than for a pagetable, we
> win.
> 
> iow, can we just nuke 'em?

Page allocator still requires interrupts to be disabled, which this doesn't.

Considering there isn't much else that frees known zeroed pages, I wonder if
it is worthwhile.

Last time the zeroidle discussion came up was IIRC not actually real performance
gain, just cooking the 1024 CPU threaded pagefault numbers ;)

-- 
SUSE Labs, Novell Inc.
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