From mboxrd@z Thu Jan 1 00:00:00 1970 From: Omar Sandoval Subject: Re: [PATCH V6 5/5] blk-mq-sched: don't dequeue request until all in ->dispatch are flushed Date: Tue, 10 Oct 2017 11:26:48 -0700 Message-ID: <20171010182648.GE30738@vader.DHCP.thefacebook.com> References: <20171009112424.30524-1-ming.lei@redhat.com> <20171009112424.30524-6-ming.lei@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20171009112424.30524-6-ming.lei@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig , Mike Snitzer , dm-devel@redhat.com, Bart Van Assche , Laurence Oberman , Paolo Valente , Oleksandr Natalenko , Tom Nguyen , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, Omar Sandoval List-Id: linux-scsi@vger.kernel.org On Mon, Oct 09, 2017 at 07:24:24PM +0800, Ming Lei wrote: > During dispatching, we moved all requests from hctx->dispatch to > one temporary list, then dispatch them one by one from this list. > Unfortunately during this period, run queue from other contexts > may think the queue is idle, then start to dequeue from sw/scheduler > queue and still try to dispatch because ->dispatch is empty. This way > hurts sequential I/O performance because requests are dequeued when > lld queue is busy. > > This patch introduces the state of BLK_MQ_S_DISPATCH_BUSY to > make sure that request isn't dequeued until ->dispatch is > flushed. > > Reviewed-by: Bart Van Assche > Reviewed-by: Christoph Hellwig I think this will do for now. Reviewed-by: Omar Sandoval > Signed-off-by: Ming Lei > --- > block/blk-mq-debugfs.c | 1 + > block/blk-mq-sched.c | 38 ++++++++++++++++++++++++++++++++------ > block/blk-mq.c | 5 +++++ > include/linux/blk-mq.h | 1 + > 4 files changed, 39 insertions(+), 6 deletions(-)