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    Subject[08/17] Pass vmalloc address in page->private
    Avoid expensive lookups of virtual addresses from page structs by
    storing the vmalloc address in page->private. We can then avoid
    the vmalloc_address() in the get_xxxx_pagexxxx() functions and
    simply return page->private.

    Signed-off-by: Christoph Lameter <clameter@sgi.com>

    ---
    mm/page_alloc.c | 15 ++++++++++++---
    1 file changed, 12 insertions(+), 3 deletions(-)

    Index: linux-2.6/mm/page_alloc.c
    ===================================================================
    --- linux-2.6.orig/mm/page_alloc.c 2007-09-18 18:35:55.000000000 -0700
    +++ linux-2.6/mm/page_alloc.c 2007-09-18 18:36:01.000000000 -0700
    @@ -1276,6 +1276,11 @@ struct page *vcompound_alloc(gfp_t gfp_m
    if (!addr)
    goto abort;

    + /*
    + * Give the caller a chance to avoid an expensive vmalloc_addr()
    + * call.
    + */
    + pages[0]->private = (unsigned long)addr;
    return pages[0];

    abort:
    @@ -1534,6 +1539,8 @@ fastcall unsigned long __get_free_pages(
    page = alloc_pages(gfp_mask, order);
    if (!page)
    return 0;
    + if (unlikely(PageVcompound(page)))
    + return page->private;
    return (unsigned long) page_address(page);
    }

    @@ -1550,9 +1557,11 @@ fastcall unsigned long get_zeroed_page(g
    VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);

    page = alloc_pages(gfp_mask | __GFP_ZERO, 0);
    - if (page)
    - return (unsigned long) page_address(page);
    - return 0;
    + if (!page)
    + return 0;
    + if (unlikely(PageVcompound(page)))
    + return page->private;
    + return (unsigned long) page_address(page);
    }

    EXPORT_SYMBOL(get_zeroed_page);
    --
    -
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