[lkml]   [2008]   [Jun]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH] splitlru: BDI_CAP_SWAP_BACKED
    > The split-lru patches put file and swap-backed pages on different lrus.
    > shmem/tmpfs pages are awkward because they are swap-backed file pages.
    > Since it's difficult to change lru midstream, they are treated as swap-
    > backed throughout, with SetPageSwapBacked on allocation in shmem_getpage.
    > However, splice read (used by loop and sendfile) and readahead* allocate
    > pages first, add_to_page_cache_lru, and then call into the filesystem
    > through ->readpage. Under memory pressure, the shmem pages arrive at
    > add_to_swap_cache and hit its BUG_ON(!PageSwapBacked(page)).
    > I've not yet found a better way to handle this than a "capability"
    > flag in shmem_backing_dev_info, tested by add_to_page_cache_lru.
    > And solely because it would look suspicious without it, set that
    > BDI_CAP_SWAP_BACKED in swap_backing_dev_info also.
    > * readahead on shmem/tmpfs? I'd always thought ra_pages 0 prevented
    > that; but in fact readahead(2), fadvise(POSIX_FADV_WILLNEED) and
    > madvise(MADV_WILLNEED) all force_page_cache_readahead and get there.
    > Signed-off-by: Hugh Dickins <>


    I'm not sure about this patch is perfect.
    but it seems makes sense and very good code.

    So, I'll testing this patch for a while.

    Rik, What do you think about it?

     \ /
      Last update: 2008-06-29 10:53    [W:0.024 / U:6.492 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site