Re: [PATCH 30/35] Skip the PCP list search by counting the orderand type of pages on list

From: Mel Gorman
Date: Mon Mar 16 2009 - 12:51:20 EST


On Mon, Mar 16, 2009 at 12:31:44PM -0400, Christoph Lameter wrote:
> On Mon, 16 Mar 2009, Mel Gorman wrote:
>
> >
> > struct per_cpu_pages {
> > - int count; /* number of pages in the list */
> > + /* The total number of pages on the PCP lists */
> > + int count;
> > +
> > + /* Count of each migratetype and order */
> > + u8 mocount[MIGRATE_PCPTYPES][PAGE_ALLOC_COSTLY_ORDER+1];
>
> What about overflow? You could have more than 255 pages of a given type in
> a pcp.
>

Are you sure? The maximum size I would expect is pcp->high which is
6 * pcp->batch which is limited in size. I might have missed something
though.

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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