From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH v3] block, dm: don't copy bios for request clones Date: Tue, 28 Apr 2015 07:49:56 +0200 Message-ID: <553F1F84.6020007@suse.de> References: <1429957432-20672-1-git-send-email-hch@lst.de> <20150428005950.GA31039@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20150428005950.GA31039@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development , Christoph Hellwig Cc: Jens Axboe List-Id: dm-devel.ids On 04/28/2015 02:59 AM, Mike Snitzer wrote: > From: Christoph Hellwig > = > Currently dm-multipath has to clone the bios for every request sent > to the lower devices, which wastes cpu cycles and ties down memory. > = > This patch instead adds a new REQ_CLONE flag that instructs req_bio_endio > to not complete bios attached to a request, which we set on clone > requests similar to bios in a flush sequence. With this change I/O > errors on a path failure only get propagated to dm-multipath, which > can then either resubmit the I/O or complete the bios on the original > request. > = > I've done some basic testing of this on a Linux target with ALUA support, > and it survives path failures during I/O nicely. > = > Signed-off-by: Christoph Hellwig > Signed-off-by: Mike Snitzer Reviewed-by: Hannes Reinecke Cheers, Hannes -- = Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: F. Imend=F6rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG N=FCrnberg)