On Tue, Apr 05, 2022 at 02:31:22PM +0900, Suwan Kim wrote: > This patch supports mq_ops->queue_rqs() hook. It has an advantage of > batch submission to virtio-blk driver. It also helps polling I/O because > polling uses batched completion of block layer. Batch submission in > queue_rqs() can boost polling performance. > > In queue_rqs(), it iterates plug->mq_list, collects requests that > belong to same HW queue until it encounters a request from other > HW queue or sees the end of the list. > Then, virtio-blk adds requests into virtqueue and kicks virtqueue > to submit requests. > > If there is an error, it inserts error request to requeue_list and > passes it to ordinary block layer path. > > For verification, I did fio test. > (io_uring, randread, direct=1, bs=4K, iodepth=64 numjobs=N) > I set 4 vcpu and 2 virtio-blk queues for VM and run fio test 5 times. > It shows about 2% improvement. > > | numjobs=2 | numjobs=4 > ----------------------------------------------------------- > fio without queue_rqs() | 291K IOPS | 238K IOPS > ----------------------------------------------------------- > fio with queue_rqs() | 295K IOPS | 243K IOPS > > For polling I/O performance, I also did fio test as below. > (io_uring, hipri, randread, direct=1, bs=512, iodepth=64 numjobs=4) > I set 4 vcpu and 2 poll queues for VM. > It shows about 2% improvement in polling I/O. > > | IOPS | avg latency > ----------------------------------------------------------- > fio poll without queue_rqs() | 424K | 613.05 usec > ----------------------------------------------------------- > fio poll with queue_rqs() | 435K | 601.01 usec > > Signed-off-by: Suwan Kim <[email protected]> > --- > drivers/block/virtio_blk.c | 110 +++++++++++++++++++++++++++++++++---- > 1 file changed, 99 insertions(+), 11 deletions(-) > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 712579dcd3cc..a091034bc551 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -92,6 +92,7 @@ struct virtio_blk { > struct virtblk_req { > struct virtio_blk_outhdr out_hdr; > u8 status; > + int sg_num; > struct sg_table sg_table; > struct scatterlist sg[]; > }; > @@ -311,18 +312,13 @@ static void virtio_commit_rqs(struct blk_mq_hw_ctx > *hctx) > virtqueue_notify(vq->vq); > } > > -static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx, > - const struct blk_mq_queue_data *bd) > +static blk_status_t virtblk_prep_rq(struct blk_mq_hw_ctx *hctx, > + struct virtio_blk *vblk, > + struct request *req, > + struct virtblk_req *vbr) > { > - struct virtio_blk *vblk = hctx->queue->queuedata; > - struct request *req = bd->rq; > - struct virtblk_req *vbr = blk_mq_rq_to_pdu(req); > - unsigned long flags; > - int num; > - int qid = hctx->queue_num; > - bool notify = false; > blk_status_t status; > - int err; > + int num; > > status = virtblk_setup_cmd(vblk->vdev, req, vbr); > if (unlikely(status)) > @@ -335,9 +331,30 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx > *hctx, > virtblk_cleanup_cmd(req); > return BLK_STS_RESOURCE; > } > + vbr->sg_num = num;
This can go into the nents field of vbr->sg_table. > + int err; > + > + status = virtblk_prep_rq(hctx, vblk, req, vbr); > + if (unlikely(status)) > + return status; > > spin_lock_irqsave(&vblk->vqs[qid].lock, flags); > - err = virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg_table.sgl, num); > + err = virtblk_add_req(vblk->vqs[qid].vq, vbr, > + vbr->sg_table.sgl, vbr->sg_num); And while we're at it - virtblk_add_req can lose the data_sg and have_data arguments as they can be derived from vbr. _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
