• Steven Whitehouse's avatar
    [GFS2] Shrink gfs2_inode memory by half · fee852e3
    Steven Whitehouse authored
    Here is something I spotted (while looking for something entirely
    different) the other day.
    
    Rather than using a completion in each and every struct gfs2_holder,
    this removes it in favour of hashed wait queues, thus saving a
    considerable amount of memory both on the stack (where a number of
    gfs2_holder structures are allocated) and in particular in the
    gfs2_inode which has 8 gfs2_holder structures embedded within it.
    
    As a result on x86_64 the gfs2_inode shrinks from 2488 bytes to
    1912 bytes, a saving of 576 bytes per inode (no thats not a typo!).
    In actual practice we get a much better result than that since
    now that a gfs2_inode is under the 2048 byte barrier, we get two
    per 4k slab page effectively halving the amount of memory required
    to store gfs2_inodes.
    Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
    fee852e3
incore.h 14.9 KB