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

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Date:	Tue, 13 Mar 2007 14:36:11 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Matt Mackall <mpm@...enic.com>
CC:	David Miller <davem@...emloft.net>, nickpiggin@...oo.com.au,
	akpm@...ux-foundation.org, clameter@....com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [QUICKLIST 0/4] Arch independent quicklists V2

Matt Mackall wrote:
> Well you -could- do this:
>
> - reuse a long in struct page as a used map that divides the page up
>   into 32 or 64 segments
> - every time you set a PTE, set the corresponding bit in the mask
> - when we zap, only visit the regions set in the mask
>
> Thus, you avoid visiting most of a PMD page in the sparse case,
> assuming PTEs aren't evenly spread across the PMD.
>
> This might not even be too horrible as the appropriate struct page
> should be in cache with the appropriate bits of the mm already locked,
> etc.
>   

And do the same in pte pages for actual mapped pages?  Or do you think
they would be too densely populated for it to be worthwhile?

    J

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