Commits
Mike Snitzer committed b88efd43f90
dm mpath: delay the requeue of blk-mq requests while all paths down Return DM_MAPIO_DELAY_REQUEUE from .clone_and_map_rq. Also, return false from .busy, if all paths are down, so that blk-mq requests get mapped via .clone_and_map_rq -- which results in DM_MAPIO_DELAY_REQUEUE being returned to dm-rq. This change allows for a noticeable reduction in cpu utilization (reduced kworker load) while all paths are down, e.g.: system CPU idleness (as measured by fio's --idle-prof=system): before: system: 86.58% after: system: 98.60% Signed-off-by: Mike Snitzer <snitzer@redhat.com> Reviewed-by: Hannes Reinecke <hare@suse.com>