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    SubjectRe: [patch 3/3] mm: keep pages from unevictable mappings off the LRU lists
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    > On Mon, Mar 23, 2009 at 11:21:36AM +0900, KOSAKI Motohiro wrote:
    > > > Hmm,,
    > > >
    > > > This patch is another thing unlike previous series patches.
    > > > Firstly, It looked good to me.
    > > >
    > > > I think add_to_page_cache_lru have to become a fast path.
    > > > But, how often would ramfs and shmem function be called ?
    > > >
    > > > I have a concern for this patch to add another burden.
    > > > so, we need any numbers for getting pros and cons.
    > > >
    > > > Any thoughts ?
    > >
    > > this is the just reason why current code don't call add_page_to_unevictable_list().
    > > add_page_to_unevictable_list() don't use pagevec. it is needed for avoiding race.
    > >
    > > then, if readahead path (i.e. add_to_page_cache_lru()) use add_page_to_unevictable_list(),
    > > it can cause zone->lru_lock contention storm.
    >
    > How is it different then shrink_page_list()? If readahead put a
    > contiguous chunk of unevictable pages to the file lru, then
    > shrink_page_list() will as well call add_page_to_unevictable_list() in
    > a loop.

    it's probability issue.

    readahead: we need to concern
    (1) readahead vs readahead
    (2) readahead vs reclaim

    vmscan: we need to concern
    (3) background reclaim vs foreground reclaim

    So, (3) is rarely event than (1) and (2).
    Am I missing anything?





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