Messages in this thread | | | Date | Mon, 16 Mar 2009 16:52:20 +0000 | From | Mel Gorman <> | Subject | Re: [PATCH 31/35] Optimistically check the first page on the PCP free list is suitable |
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On Mon, Mar 16, 2009 at 12:33:44PM -0400, Christoph Lameter wrote: > On Mon, 16 Mar 2009, Mel Gorman wrote: > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index bb5bd5e..8568284 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1212,6 +1212,12 @@ again: > > if (pcp_page_suit(page, order)) > > break; > > } else { > > + /* Optimistic before we start a list search */ > > + page = list_entry(list->next, struct page, lru); > > + if (pcp_page_suit(page, order)) > > + goto found; > > + > > + /* Do the search */ > > list_for_each_entry(page, list, lru) > > if (pcp_page_suit(page, order)) > > break; > > I am not convinced that this is beneficial. If it would then the compiler > would unroll the loop. >
It hit a large number of times when I checked (although I don't have the figures any more) and the list_for_each_entry() does a prefetch possibly fetching in a line we don't need.
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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