On Thu, Aug 01, 2024 at 06:39:16PM +0300, Max Gurtovoy wrote: > > On 01/08/2024 18:29, Michael S. Tsirkin wrote: > > On Thu, Aug 01, 2024 at 06:17:21PM +0300, Max Gurtovoy wrote: > > > On 01/08/2024 18:13, Michael S. Tsirkin wrote: > > > > On Thu, Aug 01, 2024 at 06:11:37PM +0300, Max Gurtovoy wrote: > > > > > In this operation set the driver data of the hctx to point to the > > > > > virtio > > > > > block queue. By doing so, we can use this reference in the and reduce > > > > in the .... ? > > > sorry for the type. > > > > > > should be : > > > > > > "By doing so, we can use this reference and reduce the number of > > > operations in the fast path." > > ok. what kind of benefit do you see with this patch? > > As mentioned. This is a micro optimization that reduce the number of > instructions/dereferences in the fast path.
By how much? How random code tweaks affect object code is unpredictable. Pls show results of objdump to prove it does anything useful. > > > > > > > > the number of operations in the fast path. > > > > > > > > > > Signed-off-by: Max Gurtovoy <[email protected]> > > > > > --- > > > > > drivers/block/virtio_blk.c | 42 > > > > > ++++++++++++++++++++------------------ > > > > > 1 file changed, 22 insertions(+), 20 deletions(-) > > > > > > > > > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > > > > > index 2351f411fa46..35a7a586f6f5 100644 > > > > > --- a/drivers/block/virtio_blk.c > > > > > +++ b/drivers/block/virtio_blk.c > > > > > @@ -129,14 +129,6 @@ static inline blk_status_t virtblk_result(u8 > > > > > status) > > > > > } > > > > > } > > > > > -static inline struct virtio_blk_vq *get_virtio_blk_vq(struct > > > > > blk_mq_hw_ctx *hctx) > > > > > -{ > > > > > - struct virtio_blk *vblk = hctx->queue->queuedata; > > > > > - struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num]; > > > > > - > > > > > - return vq; > > > > > -} > > > > > - > > > > > static int virtblk_add_req(struct virtqueue *vq, struct > > > > > virtblk_req *vbr) > > > > > { > > > > > struct scatterlist out_hdr, in_hdr, *sgs[3]; > > > > > @@ -377,8 +369,7 @@ static void virtblk_done(struct virtqueue *vq) > > > > > static void virtio_commit_rqs(struct blk_mq_hw_ctx *hctx) > > > > > { > > > > > - struct virtio_blk *vblk = hctx->queue->queuedata; > > > > > - struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num]; > > > > > + struct virtio_blk_vq *vq = hctx->driver_data; > > > > > bool kick; > > > > > spin_lock_irq(&vq->lock); > > > > > @@ -428,10 +419,10 @@ static blk_status_t virtio_queue_rq(struct > > > > > blk_mq_hw_ctx *hctx, > > > > > const struct blk_mq_queue_data *bd) > > > > > { > > > > > struct virtio_blk *vblk = hctx->queue->queuedata; > > > > > + struct virtio_blk_vq *vq = hctx->driver_data; > > > > > struct request *req = bd->rq; > > > > > struct virtblk_req *vbr = blk_mq_rq_to_pdu(req); > > > > > unsigned long flags; > > > > > - int qid = hctx->queue_num; > > > > > bool notify = false; > > > > > blk_status_t status; > > > > > int err; > > > > > @@ -440,26 +431,26 @@ static blk_status_t virtio_queue_rq(struct > > > > > blk_mq_hw_ctx *hctx, > > > > > if (unlikely(status)) > > > > > return status; > > > > > - spin_lock_irqsave(&vblk->vqs[qid].lock, flags); > > > > > - err = virtblk_add_req(vblk->vqs[qid].vq, vbr); > > > > > + spin_lock_irqsave(&vq->lock, flags); > > > > > + err = virtblk_add_req(vq->vq, vbr); > > > > > if (err) { > > > > > - virtqueue_kick(vblk->vqs[qid].vq); > > > > > + virtqueue_kick(vq->vq); > > > > > /* Don't stop the queue if -ENOMEM: we may have failed > > > > > to > > > > > * bounce the buffer due to global resource outage. > > > > > */ > > > > > if (err == -ENOSPC) > > > > > blk_mq_stop_hw_queue(hctx); > > > > > - spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags); > > > > > + spin_unlock_irqrestore(&vq->lock, flags); > > > > > virtblk_unmap_data(req, vbr); > > > > > return virtblk_fail_to_queue(req, err); > > > > > } > > > > > - if (bd->last && virtqueue_kick_prepare(vblk->vqs[qid].vq)) > > > > > + if (bd->last && virtqueue_kick_prepare(vq->vq)) > > > > > notify = true; > > > > > - spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags); > > > > > + spin_unlock_irqrestore(&vq->lock, flags); > > > > > if (notify) > > > > > - virtqueue_notify(vblk->vqs[qid].vq); > > > > > + virtqueue_notify(vq->vq); > > > > > return BLK_STS_OK; > > > > > } > > > > > @@ -504,7 +495,7 @@ static void virtio_queue_rqs(struct request > > > > > **rqlist) > > > > > struct request *requeue_list = NULL; > > > > > rq_list_for_each_safe(rqlist, req, next) { > > > > > - struct virtio_blk_vq *vq = > > > > > get_virtio_blk_vq(req->mq_hctx); > > > > > + struct virtio_blk_vq *vq = req->mq_hctx->driver_data; > > > > > bool kick; > > > > > if (!virtblk_prep_rq_batch(req)) { > > > > > @@ -1164,6 +1155,16 @@ static const struct attribute_group > > > > > *virtblk_attr_groups[] = { > > > > > NULL, > > > > > }; > > > > > +static int virtblk_init_hctx(struct blk_mq_hw_ctx *hctx, void *data, > > > > > + unsigned int hctx_idx) > > > > > +{ > > > > > + struct virtio_blk *vblk = data; > > > > > + struct virtio_blk_vq *vq = &vblk->vqs[hctx_idx]; > > > > > + > > > > > + hctx->driver_data = vq; > > > > > + return 0; > > > > > +} > > > > > + > > > > > static void virtblk_map_queues(struct blk_mq_tag_set *set) > > > > > { > > > > > struct virtio_blk *vblk = set->driver_data; > > > > > @@ -1205,7 +1206,7 @@ static void virtblk_complete_batch(struct > > > > > io_comp_batch *iob) > > > > > static int virtblk_poll(struct blk_mq_hw_ctx *hctx, struct > > > > > io_comp_batch *iob) > > > > > { > > > > > struct virtio_blk *vblk = hctx->queue->queuedata; > > > > > - struct virtio_blk_vq *vq = get_virtio_blk_vq(hctx); > > > > > + struct virtio_blk_vq *vq = hctx->driver_data; > > > > > struct virtblk_req *vbr; > > > > > unsigned long flags; > > > > > unsigned int len; > > > > > @@ -1236,6 +1237,7 @@ static const struct blk_mq_ops virtio_mq_ops = { > > > > > .queue_rqs = virtio_queue_rqs, > > > > > .commit_rqs = virtio_commit_rqs, > > > > > .complete = virtblk_request_done, > > > > > + .init_hctx = virtblk_init_hctx, > > > > > .map_queues = virtblk_map_queues, > > > > > .poll = virtblk_poll, > > > > > }; > > > > > -- > > > > > 2.18.1
