• Dave Chinner's avatar
    xfs: Throttle commits on delayed background CIL push · 0e7ab7ef
    Dave Chinner authored
    In certain situations the background CIL push can be indefinitely
    delayed. While we have workarounds from the obvious cases now, it
    doesn't solve the underlying issue. This issue is that there is no
    upper limit on the CIL where we will either force or wait for
    a background push to start, hence allowing the CIL to grow without
    bound until it consumes all log space.
    
    To fix this, add a new wait queue to the CIL which allows background
    pushes to wait for the CIL context to be switched out. This happens
    when the push starts, so it will allow us to block incoming
    transaction commit completion until the push has started. This will
    only affect processes that are running modifications, and only when
    the CIL threshold has been significantly overrun.
    
    This has no apparent impact on performance, and doesn't even trigger
    until over 45 million inodes had been created in a 16-way fsmark
    test on a 2GB log. That was limiting at 64MB of log space used, so
    the active CIL size is only about 3% of the total log in that case.
    The concurrent removal of those files did not trigger the background
    sleep at all.
    Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
    Reviewed-by: default avatarAllison Collins <allison.henderson@oracle.com>
    Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
    Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
    0e7ab7ef