• Steven Whitehouse's avatar
    [GFS2] Clean up/speed up readdir · 3699e3a4
    Steven Whitehouse authored
    This removes the extra filldir callback which gfs2 was using to
    enclose an attempt at readahead for inodes during readdir. The
    code was too complicated and also hurts performance badly in the
    case that the getdents64/readdir call isn't being followed by
    stat() and it wasn't even getting it right all the time when it
    As a result, on my test box an "ls" of a directory containing 250000
    files fell from about 7mins (freshly mounted, so nothing cached) to
    between about 15 to 25 seconds. When the directory content was cached,
    the time taken fell from about 3mins to about 4 or 5 seconds.
    Interestingly in the cached case, running "ls -l" once reduced the time
    taken for subsequent runs of "ls" to about 6 secs even without this
    patch. Now it turns out that there was a special case of glocks being
    used for prefetching the metadata, but because of the timeouts for these
    locks (set to 10 secs) the metadata was being timed out before it was
    being used and this the prefetch code was constantly trying to prefetch
    the same data over and over.
    Calling "ls -l" meant that the inodes were brought into memory and once
    the inodes are cached, the glocks are not disposed of until the inodes
    are pushed out of the cache, thus extending the lifetime of the glocks,
    and thus bringing down the time for subsequent runs of "ls"
    Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>