lkml.org 
[lkml]   [2009]   [Mar]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 31/35] Optimistically check the first page on the PCP free list is suitable
    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


    \
     
     \ /
      Last update: 2009-03-16 17:55    [W:0.022 / U:31.996 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site