• Josef Bacik's avatar
    Btrfs: throttle delayed refs better · 0a2b2a84
    Josef Bacik authored
    On one of our gluster clusters we noticed some pretty big lag spikes.  This
    turned out to be because our transaction commit was taking like 3 minutes to
    complete.  This is because we have like 30 gigs of metadata, so our global
    reserve would end up being the max which is like 512 mb.  So our throttling code
    would allow a ridiculous amount of delayed refs to build up and then they'd all
    get run at transaction commit time, and for a cold mounted file system that
    could take up to 3 minutes to run.  So fix the throttling to be based on both
    the size of the global reserve and how long it takes us to run delayed refs.
    This patch tracks the time it takes to run delayed refs and then only allows 1
    seconds worth of outstanding delayed refs at a time.  This way it will auto-tune
    itself from cold cache up to when everything is in memory and it no longer has
    to go to disk.  This makes our transaction commits take much less time to run.
    Thanks,
    Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
    Signed-off-by: default avatarChris Mason <clm@fb.com>
    0a2b2a84
disk-io.c 111 KB