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    SubjectRe: [PATCH] stop page_state stack waste
    Hugh Dickins <hugh@veritas.com> wrote:
    >
    > Replace get_page_state (which memset most of full page_state to 0) by
    > get_main_page_state, which just sets the small structure needed. This
    > helps 4k stacks not to overflow: cuts 224 bytes off try_to_free_pages
    > and wakeup_bdflush (and sync_inodes_sb) stack usages: wakeup_bdflush
    > doesn't do much, but is called by try_to_free_pages and mempool_alloc.

    Yeah, I was looking at that. I simply did:



    The ____cacheline_aligned in there is a leftover from before the existence of
    the percpu infrastructure. It bloats struct page_state and structures which
    contain it enormously, and we use these things on the stack deep in page
    reclaim.

    Signed-off-by: Andrew Morton <akpm@osdl.org>
    ---

    25-akpm/include/linux/page-flags.h | 2 +-
    1 files changed, 1 insertion(+), 1 deletion(-)

    diff -puN include/linux/page-flags.h~unalign-page_state include/linux/page-flags.h
    --- 25/include/linux/page-flags.h~unalign-page_state 2004-06-08 03:08:02.766976760 -0700
    +++ 25-akpm/include/linux/page-flags.h 2004-06-08 03:08:02.769976304 -0700
    @@ -133,7 +133,7 @@ struct page_state {
    unsigned long allocstall; /* direct reclaim calls */

    unsigned long pgrotated; /* pages rotated to tail of the LRU */
    -} ____cacheline_aligned;
    +};

    DECLARE_PER_CPU(struct page_state, page_states);

    _
    -
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