From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9BD5BC43441 for ; Thu, 29 Nov 2018 01:23:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 68EF220863 for ; Thu, 29 Nov 2018 01:23:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 68EF220863 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-block-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726872AbeK2M10 (ORCPT ); Thu, 29 Nov 2018 07:27:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49100 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726565AbeK2M10 (ORCPT ); Thu, 29 Nov 2018 07:27:26 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 556D0369CF; Thu, 29 Nov 2018 01:23:52 +0000 (UTC) Received: from ming.t460p (ovpn-8-23.pek2.redhat.com [10.72.8.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5061460C61; Thu, 29 Nov 2018 01:23:46 +0000 (UTC) Date: Thu, 29 Nov 2018 09:23:43 +0800 From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-nvme@lists.infradead.org Subject: Re: [PATCH 5/8] virtio_blk: implement mq_ops->commit_rqs() hook Message-ID: <20181129012342.GB23249@ming.t460p> References: <20181126163556.5181-1-axboe@kernel.dk> <20181126163556.5181-6-axboe@kernel.dk> <20181128021029.GF11128@ming.t460p> <35b33a34-9e24-5acb-7a4e-57433328bf3d@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <35b33a34-9e24-5acb-7a4e-57433328bf3d@kernel.dk> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 29 Nov 2018 01:23:52 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Nov 27, 2018 at 07:34:51PM -0700, Jens Axboe wrote: > On 11/27/18 7:10 PM, Ming Lei wrote: > > On Mon, Nov 26, 2018 at 09:35:53AM -0700, Jens Axboe wrote: > >> We need this for blk-mq to kick things into gear, if we told it that > >> we had more IO coming, but then failed to deliver on that promise. > >> > >> Signed-off-by: Jens Axboe > >> --- > >> drivers/block/virtio_blk.c | 15 +++++++++++++++ > >> 1 file changed, 15 insertions(+) > >> > >> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > >> index 6e869d05f91e..b49c57e77780 100644 > >> --- a/drivers/block/virtio_blk.c > >> +++ b/drivers/block/virtio_blk.c > >> @@ -214,6 +214,20 @@ static void virtblk_done(struct virtqueue *vq) > >> spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags); > >> } > >> > >> +static void virtio_commit_rqs(struct blk_mq_hw_ctx *hctx) > >> +{ > >> + struct virtio_blk *vblk = hctx->queue->queuedata; > >> + int qid = hctx->queue_num; > >> + bool kick; > >> + > >> + spin_lock_irq(&vblk->vqs[qid].lock); > >> + kick = virtqueue_kick_prepare(vblk->vqs[qid].vq); > >> + spin_unlock_irq(&vblk->vqs[qid].lock); > >> + > >> + if (kick) > >> + virtqueue_notify(vblk->vqs[qid].vq); > >> +} > >> + > >> static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx, > >> const struct blk_mq_queue_data *bd) > >> { > >> @@ -638,6 +652,7 @@ static void virtblk_initialize_rq(struct request *req) > >> > >> static const struct blk_mq_ops virtio_mq_ops = { > >> .queue_rq = virtio_queue_rq, > >> + .commit_rqs = virtio_commit_rqs, > >> .complete = virtblk_request_done, > >> .init_request = virtblk_init_request, > >> #ifdef CONFIG_VIRTIO_BLK_SCSI > >> -- > >> 2.17.1 > >> > > > > If .commit_rqs() is implemented, virtqueue_notify() in virtio_queue_rq() > > should have been removed for saving the world switch per .queue_rq() > > ->commits_rqs() is only for the case where bd->last is set to false, > and we never make it to the end and flag bd->last == true. If bd->last > is true, the driver should kick things into gear. OK, looks I misunderstood it. However, virtio-blk doesn't need this change since virtio_queue_rq() can handle it well. This patch may introduce one unnecessary VM world switch in case of queue busy. IMO bd->last won't work well in case of io scheduler given the rq_list only includes one single request. I wrote this kind of patch(never posted) before to use sort of ->commits_rqs() to replace the current bd->last mechanism which need one extra driver tag, which may improve the above case, also code gets cleaned up. Thanks, Ming From mboxrd@z Thu Jan 1 00:00:00 1970 From: ming.lei@redhat.com (Ming Lei) Date: Thu, 29 Nov 2018 09:23:43 +0800 Subject: [PATCH 5/8] virtio_blk: implement mq_ops->commit_rqs() hook In-Reply-To: <35b33a34-9e24-5acb-7a4e-57433328bf3d@kernel.dk> References: <20181126163556.5181-1-axboe@kernel.dk> <20181126163556.5181-6-axboe@kernel.dk> <20181128021029.GF11128@ming.t460p> <35b33a34-9e24-5acb-7a4e-57433328bf3d@kernel.dk> Message-ID: <20181129012342.GB23249@ming.t460p> On Tue, Nov 27, 2018@07:34:51PM -0700, Jens Axboe wrote: > On 11/27/18 7:10 PM, Ming Lei wrote: > > On Mon, Nov 26, 2018@09:35:53AM -0700, Jens Axboe wrote: > >> We need this for blk-mq to kick things into gear, if we told it that > >> we had more IO coming, but then failed to deliver on that promise. > >> > >> Signed-off-by: Jens Axboe > >> --- > >> drivers/block/virtio_blk.c | 15 +++++++++++++++ > >> 1 file changed, 15 insertions(+) > >> > >> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > >> index 6e869d05f91e..b49c57e77780 100644 > >> --- a/drivers/block/virtio_blk.c > >> +++ b/drivers/block/virtio_blk.c > >> @@ -214,6 +214,20 @@ static void virtblk_done(struct virtqueue *vq) > >> spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags); > >> } > >> > >> +static void virtio_commit_rqs(struct blk_mq_hw_ctx *hctx) > >> +{ > >> + struct virtio_blk *vblk = hctx->queue->queuedata; > >> + int qid = hctx->queue_num; > >> + bool kick; > >> + > >> + spin_lock_irq(&vblk->vqs[qid].lock); > >> + kick = virtqueue_kick_prepare(vblk->vqs[qid].vq); > >> + spin_unlock_irq(&vblk->vqs[qid].lock); > >> + > >> + if (kick) > >> + virtqueue_notify(vblk->vqs[qid].vq); > >> +} > >> + > >> static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx, > >> const struct blk_mq_queue_data *bd) > >> { > >> @@ -638,6 +652,7 @@ static void virtblk_initialize_rq(struct request *req) > >> > >> static const struct blk_mq_ops virtio_mq_ops = { > >> .queue_rq = virtio_queue_rq, > >> + .commit_rqs = virtio_commit_rqs, > >> .complete = virtblk_request_done, > >> .init_request = virtblk_init_request, > >> #ifdef CONFIG_VIRTIO_BLK_SCSI > >> -- > >> 2.17.1 > >> > > > > If .commit_rqs() is implemented, virtqueue_notify() in virtio_queue_rq() > > should have been removed for saving the world switch per .queue_rq() > > ->commits_rqs() is only for the case where bd->last is set to false, > and we never make it to the end and flag bd->last == true. If bd->last > is true, the driver should kick things into gear. OK, looks I misunderstood it. However, virtio-blk doesn't need this change since virtio_queue_rq() can handle it well. This patch may introduce one unnecessary VM world switch in case of queue busy. IMO bd->last won't work well in case of io scheduler given the rq_list only includes one single request. I wrote this kind of patch(never posted) before to use sort of ->commits_rqs() to replace the current bd->last mechanism which need one extra driver tag, which may improve the above case, also code gets cleaned up. Thanks, Ming