| Message ID | 20241113152050.157179-3-hch@lst.de (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/6] nvme-pci: reverse request order in nvme_queue_rqs | expand |
On Wed, Nov 13, 2024 at 04:20:42PM +0100, Christoph Hellwig wrote:
> in rotational devices. Fix this by rewriting nvme_queue_rqs so that it
You copied this commit message from the previous one for the nvme
driver. This message should say "virtio_queue_rqs".
On 11/13/24 12:03 PM, Keith Busch wrote: > On Wed, Nov 13, 2024 at 04:20:42PM +0100, Christoph Hellwig wrote: >> in rotational devices. Fix this by rewriting nvme_queue_rqs so that it > > You copied this commit message from the previous one for the nvme > driver. This message should say "virtio_queue_rqs". I fixed it up. As well as the annoying "two spaces after a period", that should just go away.
On Wed, Nov 13, 2024 at 04:20:42PM +0100, Christoph Hellwig wrote: > blk_mq_flush_plug_list submits requests in the reverse order that they > were submitted, which leads to a rather suboptimal I/O pattern especially > in rotational devices. Fix this by rewriting nvme_queue_rqs so that it > always pops the requests from the passed in request list, and then adds > them to the head of a local submit list. This actually simplifies the > code a bit as it removes the complicated list splicing, at the cost of > extra updates of the rq_next pointer. As that should be cache hot > anyway it should be an easy price to pay. > > Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()") > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > drivers/block/virtio_blk.c | 46 +++++++++++++++++--------------------- > 1 file changed, 21 insertions(+), 25 deletions(-) > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 0e99a4714928..b25f7c06a28e 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -471,18 +471,18 @@ static bool virtblk_prep_rq_batch(struct request *req) > return virtblk_prep_rq(req->mq_hctx, vblk, req, vbr) == BLK_STS_OK; > } > > -static bool virtblk_add_req_batch(struct virtio_blk_vq *vq, > +static void virtblk_add_req_batch(struct virtio_blk_vq *vq, > struct request **rqlist) > { > + struct request *req; > unsigned long flags; > - int err; > bool kick; > > spin_lock_irqsave(&vq->lock, flags); > > - while (!rq_list_empty(*rqlist)) { > - struct request *req = rq_list_pop(rqlist); > + while ((req = rq_list_pop(rqlist))) { > struct virtblk_req *vbr = blk_mq_rq_to_pdu(req); > + int err; > > err = virtblk_add_req(vq->vq, vbr); > if (err) { > @@ -495,37 +495,33 @@ static bool virtblk_add_req_batch(struct virtio_blk_vq *vq, > kick = virtqueue_kick_prepare(vq->vq); > spin_unlock_irqrestore(&vq->lock, flags); > > - return kick; > + if (kick) > + virtqueue_notify(vq->vq); > } > > static void virtio_queue_rqs(struct request **rqlist) > { > - struct request *req, *next, *prev = NULL; > + struct request *submit_list = NULL; > struct request *requeue_list = NULL; > + struct request **requeue_lastp = &requeue_list; > + struct virtio_blk_vq *vq = NULL; > + struct request *req; > > - rq_list_for_each_safe(rqlist, req, next) { > - struct virtio_blk_vq *vq = get_virtio_blk_vq(req->mq_hctx); > - bool kick; > - > - if (!virtblk_prep_rq_batch(req)) { > - rq_list_move(rqlist, &requeue_list, req, prev); > - req = prev; > - if (!req) > - continue; > - } > + while ((req = rq_list_pop(rqlist))) { > + struct virtio_blk_vq *this_vq = get_virtio_blk_vq(req->mq_hctx); > > - if (!next || req->mq_hctx != next->mq_hctx) { > - req->rq_next = NULL; > - kick = virtblk_add_req_batch(vq, rqlist); > - if (kick) > - virtqueue_notify(vq->vq); > + if (vq && vq != this_vq) > + virtblk_add_req_batch(vq, &submit_list); > + vq = this_vq; > > - *rqlist = next; > - prev = NULL; > - } else > - prev = req; > + if (virtblk_prep_rq_batch(req)) > + rq_list_add(&submit_list, req); /* reverse order */ > + else > + rq_list_add_tail(&requeue_lastp, req); > } > > + if (vq) > + virtblk_add_req_batch(vq, &submit_list); > *rqlist = requeue_list; > } looks ok from virtio POV Acked-by: Michael S. Tsirkin <mst@redhat.com> > -- > 2.45.2
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 0e99a4714928..b25f7c06a28e 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -471,18 +471,18 @@ static bool virtblk_prep_rq_batch(struct request *req) return virtblk_prep_rq(req->mq_hctx, vblk, req, vbr) == BLK_STS_OK; } -static bool virtblk_add_req_batch(struct virtio_blk_vq *vq, +static void virtblk_add_req_batch(struct virtio_blk_vq *vq, struct request **rqlist) { + struct request *req; unsigned long flags; - int err; bool kick; spin_lock_irqsave(&vq->lock, flags); - while (!rq_list_empty(*rqlist)) { - struct request *req = rq_list_pop(rqlist); + while ((req = rq_list_pop(rqlist))) { struct virtblk_req *vbr = blk_mq_rq_to_pdu(req); + int err; err = virtblk_add_req(vq->vq, vbr); if (err) { @@ -495,37 +495,33 @@ static bool virtblk_add_req_batch(struct virtio_blk_vq *vq, kick = virtqueue_kick_prepare(vq->vq); spin_unlock_irqrestore(&vq->lock, flags); - return kick; + if (kick) + virtqueue_notify(vq->vq); } static void virtio_queue_rqs(struct request **rqlist) { - struct request *req, *next, *prev = NULL; + struct request *submit_list = NULL; struct request *requeue_list = NULL; + struct request **requeue_lastp = &requeue_list; + struct virtio_blk_vq *vq = NULL; + struct request *req; - rq_list_for_each_safe(rqlist, req, next) { - struct virtio_blk_vq *vq = get_virtio_blk_vq(req->mq_hctx); - bool kick; - - if (!virtblk_prep_rq_batch(req)) { - rq_list_move(rqlist, &requeue_list, req, prev); - req = prev; - if (!req) - continue; - } + while ((req = rq_list_pop(rqlist))) { + struct virtio_blk_vq *this_vq = get_virtio_blk_vq(req->mq_hctx); - if (!next || req->mq_hctx != next->mq_hctx) { - req->rq_next = NULL; - kick = virtblk_add_req_batch(vq, rqlist); - if (kick) - virtqueue_notify(vq->vq); + if (vq && vq != this_vq) + virtblk_add_req_batch(vq, &submit_list); + vq = this_vq; - *rqlist = next; - prev = NULL; - } else - prev = req; + if (virtblk_prep_rq_batch(req)) + rq_list_add(&submit_list, req); /* reverse order */ + else + rq_list_add_tail(&requeue_lastp, req); } + if (vq) + virtblk_add_req_batch(vq, &submit_list); *rqlist = requeue_list; }
blk_mq_flush_plug_list submits requests in the reverse order that they were submitted, which leads to a rather suboptimal I/O pattern especially in rotational devices. Fix this by rewriting nvme_queue_rqs so that it always pops the requests from the passed in request list, and then adds them to the head of a local submit list. This actually simplifies the code a bit as it removes the complicated list splicing, at the cost of extra updates of the rq_next pointer. As that should be cache hot anyway it should be an easy price to pay. Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()") Signed-off-by: Christoph Hellwig <hch@lst.de> --- drivers/block/virtio_blk.c | 46 +++++++++++++++++--------------------- 1 file changed, 21 insertions(+), 25 deletions(-)