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

From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Matt Mackall <mpm@selenic.com>
Cc: David Miller <davem@davemloft.net>,
	nickpiggin@yahoo.com.au, akpm@linux-foundation.org,
	clameter@sgi.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [QUICKLIST 0/4] Arch independent quicklists V2
Date: Tue, 13 Mar 2007 14:36:11 -0700	[thread overview]
Message-ID: <45F7194B.5080705@goop.org> (raw)
In-Reply-To: <20070313211435.GP10394@waste.org>

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