[dm-devel] [PATCH 3/3] dm mpath: delay the requeue of blk-mq requests while all paths down
Hannes Reinecke
hare at suse.de
Wed Sep 14 06:25:51 UTC 2016
On 09/13/2016 06:01 PM, Mike Snitzer wrote:
> 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: 87.53%
> after: system: 97.07%
>
> Signed-off-by: Mike Snitzer <snitzer at redhat.com>
> ---
> drivers/md/dm-mpath.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
Reviewed-by: Hannes Reinecke <hare at suse.com>
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare at suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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