From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH 3/3] dm mpath: delay the requeue of blk-mq requests while all paths down To: Mike Snitzer , axboe@kernel.dk, dm-devel@redhat.com References: <1473782495-44128-1-git-send-email-snitzer@redhat.com> <1473782495-44128-4-git-send-email-snitzer@redhat.com> Cc: linux-block@vger.kernel.org From: Hannes Reinecke Message-ID: Date: Wed, 14 Sep 2016 08:25:51 +0200 MIME-Version: 1.0 In-Reply-To: <1473782495-44128-4-git-send-email-snitzer@redhat.com> Content-Type: text/plain; charset=windows-1252 List-ID: 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 > --- > drivers/md/dm-mpath.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N�rnberg GF: J. Hawn, J. Guild, F. Imend�rffer, HRB 16746 (AG N�rnberg) From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH 3/3] dm mpath: delay the requeue of blk-mq requests while all paths down Date: Wed, 14 Sep 2016 08:25:51 +0200 Message-ID: References: <1473782495-44128-1-git-send-email-snitzer@redhat.com> <1473782495-44128-4-git-send-email-snitzer@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <1473782495-44128-4-git-send-email-snitzer@redhat.com> Sender: linux-block-owner@vger.kernel.org To: Mike Snitzer , axboe@kernel.dk, dm-devel@redhat.com Cc: linux-block@vger.kernel.org List-Id: dm-devel.ids 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 > --- > drivers/md/dm-mpath.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)