lkml.org 
[lkml]   [2008]   [Apr]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] xfs: use smaller int param in call to xfs_flush_pages
    On Mon, Apr 21, 2008 at 10:18:24PM -0500, Eric Sandeen wrote:
    > FWIW this one also seems to make no stack difference, at least on x86_64.
    >
    > Not complaining; just checking it out. :)
    >
    > If you can shink xfs_bmapi, let me know. :)

    FWIW, the path we care about is this path through ->writepage:

    (submit_bio)
    _xfs_buf_ioapply 32
    xfs_buf_iorequest 0
    xfs_buf_iostart 0
    xfs_buf_read_flags 0
    xfs_trans_read_buf 4
    xfs_btree_read_bufs 16
    xfs_alloc_lookup 56
    xfs_alloc_lookup_eq 16
    xfs_alloc_fixup_trees 20
    xfs_alloc_ag_vextent_near 76
    xfs_alloc_ag_vextent 0
    xfs_alloc_vextent 48
    xfs_bmap_btalloc 164
    xfs_bmap_alloc 0
    xfs_bmapi 228
    xfs_iomap_write_allocate 116
    xfs_iomap 20
    xfs_map_blocks 16
    xfs_page_state_convert 124
    xfs_vm_writepage 12
    -------------------------------------
    checkstack total: 948

    Realistically, the onyl thing we can trim anything off is xfs_bmapi,
    xfs_bmap_btalloc, xfs_iomap_write_allocate, and xfs_page_state_convert.
    It's going to take a lot of work to get any significant change into
    those functions given the complexity of them....

    FWIW, if we've come through a syscall, the rest of the trace looks
    like:

    __writepage 0
    write_cache_pages 100
    generic_writepages 0
    xfs_vm_writepages 12
    do_writepages 0
    __writeback_single_inode 36
    sync_sb_inodes 40
    writeback_inodes 0
    balance_dirty_pages_ratelimited_nr 76
    generic_file_buffered_write 96
    xfs_write 80
    xfs_file_aio_write 12
    do_sync_write 140
    vfs_write 12
    --------------------------------------------
    total 604

    So the normal case uses 604 bytes prior to entering ->writepage.

    It's when we are already using >2k of the stack when we enter
    ->writepage that we get into trouble....

    Cheers,

    Dave.
    --
    Dave Chinner
    Principal Engineer
    SGI Australian Software Group


    \
     
     \ /
      Last update: 2008-04-22 06:15    [W:0.024 / U:1.660 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site