* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data [not found] <20210901131434.31158-1-mgurtovoy@nvidia.com> @ 2021-09-01 14:50 ` Michael S. Tsirkin [not found] ` <89d6dc30-a876-b1b0-4ff4-605415113611@nvidia.com> 2021-09-02 12:21 ` Stefan Hajnoczi ` (2 subsequent siblings) 3 siblings, 1 reply; 10+ messages in thread From: Michael S. Tsirkin @ 2021-09-01 14:50 UTC (permalink / raw) To: Max Gurtovoy Cc: axboe, linux-block, kvm, israelr, virtualization, hch, nitzanc, stefanha, oren On Wed, Sep 01, 2021 at 04:14:34PM +0300, Max Gurtovoy wrote: > No need to pre-allocate a big buffer for the IO SGL anymore. If a device > has lots of deep queues, preallocation for the sg list can consume > substantial amounts of memory. For HW virtio-blk device, nr_hw_queues > can be 64 or 128 and each queue's depth might be 128. This means the > resulting preallocation for the data SGLs is big. > > Switch to runtime allocation for SGL for lists longer than 2 entries. > This is the approach used by NVMe drivers so it should be reasonable for > virtio block as well. Runtime SGL allocation has always been the case > for the legacy I/O path so this is nothing new. > > The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't > support SG_CHAIN, use only runtime allocation for the SGL. > > Re-organize the setup of the IO request to fit the new sg chain > mechanism. > > No performance degradation was seen (fio libaio engine with 16 jobs and > 128 iodepth): > > IO size IOPs Rand Read (before/after) IOPs Rand Write (before/after) > -------- --------------------------------- ---------------------------------- > 512B 318K/316K 329K/325K > > 4KB 323K/321K 353K/349K > > 16KB 199K/208K 250K/275K > > 128KB 36K/36.1K 39.2K/41.7K > > Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com> > Reviewed-by: Israel Rukshin <israelr@nvidia.com> Could you use something to give confidence intervals maybe? As it is it looks like a 1-2% regression for 512B and 4KB. > --- > > changes from V2: > - initialize vbr->out_hdr.sector during virtblk_setup_cmd > > changes from V1: > - Kconfig update (from Christoph) > - Re-order cmd setup (from Christoph) > - use flexible sg pointer in the cmd (from Christoph) > - added perf numbers to commit msg (from Feng Li) > > --- > drivers/block/Kconfig | 1 + > drivers/block/virtio_blk.c | 155 +++++++++++++++++++++++-------------- > 2 files changed, 100 insertions(+), 56 deletions(-) > > diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig > index 63056cfd4b62..ca25a122b8ee 100644 > --- a/drivers/block/Kconfig > +++ b/drivers/block/Kconfig > @@ -395,6 +395,7 @@ config XEN_BLKDEV_BACKEND > config VIRTIO_BLK > tristate "Virtio block driver" > depends on VIRTIO > + select SG_POOL > help > This is the virtual block driver for virtio. It can be used with > QEMU based VMMs (like KVM or Xen). Say Y or M. > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 9332fc4e9b31..bdd6d415bd20 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -24,6 +24,12 @@ > /* The maximum number of sg elements that fit into a virtqueue */ > #define VIRTIO_BLK_MAX_SG_ELEMS 32768 > > +#ifdef CONFIG_ARCH_NO_SG_CHAIN > +#define VIRTIO_BLK_INLINE_SG_CNT 0 > +#else > +#define VIRTIO_BLK_INLINE_SG_CNT 2 > +#endif > + > static int virtblk_queue_count_set(const char *val, > const struct kernel_param *kp) > { > @@ -93,6 +99,7 @@ struct virtio_blk { > struct virtblk_req { > struct virtio_blk_outhdr out_hdr; > u8 status; > + struct sg_table sg_table; > struct scatterlist sg[]; > }; > > @@ -178,15 +185,94 @@ static int virtblk_setup_discard_write_zeroes(struct request *req, bool unmap) > return 0; > } > > -static inline void virtblk_request_done(struct request *req) > +static void virtblk_unmap_data(struct request *req, struct virtblk_req *vbr) > { > - struct virtblk_req *vbr = blk_mq_rq_to_pdu(req); > + if (blk_rq_nr_phys_segments(req)) > + sg_free_table_chained(&vbr->sg_table, > + VIRTIO_BLK_INLINE_SG_CNT); > +} > + > +static int virtblk_map_data(struct blk_mq_hw_ctx *hctx, struct request *req, > + struct virtblk_req *vbr) > +{ > + int err; > + > + if (!blk_rq_nr_phys_segments(req)) > + return 0; > + > + vbr->sg_table.sgl = vbr->sg; > + err = sg_alloc_table_chained(&vbr->sg_table, > + blk_rq_nr_phys_segments(req), > + vbr->sg_table.sgl, > + VIRTIO_BLK_INLINE_SG_CNT); > + if (unlikely(err)) > + return -ENOMEM; > > + return blk_rq_map_sg(hctx->queue, req, vbr->sg_table.sgl); > +} > + > +static void virtblk_cleanup_cmd(struct request *req) > +{ > if (req->rq_flags & RQF_SPECIAL_PAYLOAD) { > kfree(page_address(req->special_vec.bv_page) + > req->special_vec.bv_offset); > } > +} > + > +static int virtblk_setup_cmd(struct virtio_device *vdev, struct request *req, > + struct virtblk_req *vbr) > +{ > + bool unmap = false; > + u32 type; > + > + vbr->out_hdr.sector = 0; > + > + switch (req_op(req)) { > + case REQ_OP_READ: > + type = VIRTIO_BLK_T_IN; > + vbr->out_hdr.sector = cpu_to_virtio64(vdev, > + blk_rq_pos(req)); > + break; > + case REQ_OP_WRITE: > + type = VIRTIO_BLK_T_OUT; > + vbr->out_hdr.sector = cpu_to_virtio64(vdev, > + blk_rq_pos(req)); > + break; > + case REQ_OP_FLUSH: > + type = VIRTIO_BLK_T_FLUSH; > + break; > + case REQ_OP_DISCARD: > + type = VIRTIO_BLK_T_DISCARD; > + break; > + case REQ_OP_WRITE_ZEROES: > + type = VIRTIO_BLK_T_WRITE_ZEROES; > + unmap = !(req->cmd_flags & REQ_NOUNMAP); > + break; > + case REQ_OP_DRV_IN: > + type = VIRTIO_BLK_T_GET_ID; > + break; > + default: > + WARN_ON_ONCE(1); > + return BLK_STS_IOERR; > + } > > + vbr->out_hdr.type = cpu_to_virtio32(vdev, type); > + vbr->out_hdr.ioprio = cpu_to_virtio32(vdev, req_get_ioprio(req)); > + > + if (type == VIRTIO_BLK_T_DISCARD || type == VIRTIO_BLK_T_WRITE_ZEROES) { > + if (virtblk_setup_discard_write_zeroes(req, unmap)) > + return BLK_STS_RESOURCE; > + } > + > + return 0; > +} > + > +static inline void virtblk_request_done(struct request *req) > +{ > + struct virtblk_req *vbr = blk_mq_rq_to_pdu(req); > + > + virtblk_unmap_data(req, vbr); > + virtblk_cleanup_cmd(req); > blk_mq_end_request(req, virtblk_result(vbr)); > } > > @@ -244,57 +330,23 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx, > int qid = hctx->queue_num; > int err; > bool notify = false; > - bool unmap = false; > - u32 type; > > BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems); > > - switch (req_op(req)) { > - case REQ_OP_READ: > - case REQ_OP_WRITE: > - type = 0; > - break; > - case REQ_OP_FLUSH: > - type = VIRTIO_BLK_T_FLUSH; > - break; > - case REQ_OP_DISCARD: > - type = VIRTIO_BLK_T_DISCARD; > - break; > - case REQ_OP_WRITE_ZEROES: > - type = VIRTIO_BLK_T_WRITE_ZEROES; > - unmap = !(req->cmd_flags & REQ_NOUNMAP); > - break; > - case REQ_OP_DRV_IN: > - type = VIRTIO_BLK_T_GET_ID; > - break; > - default: > - WARN_ON_ONCE(1); > - return BLK_STS_IOERR; > - } > - > - vbr->out_hdr.type = cpu_to_virtio32(vblk->vdev, type); > - vbr->out_hdr.sector = type ? > - 0 : cpu_to_virtio64(vblk->vdev, blk_rq_pos(req)); > - vbr->out_hdr.ioprio = cpu_to_virtio32(vblk->vdev, req_get_ioprio(req)); > + err = virtblk_setup_cmd(vblk->vdev, req, vbr); > + if (unlikely(err)) > + return err; > > blk_mq_start_request(req); > > - if (type == VIRTIO_BLK_T_DISCARD || type == VIRTIO_BLK_T_WRITE_ZEROES) { > - err = virtblk_setup_discard_write_zeroes(req, unmap); > - if (err) > - return BLK_STS_RESOURCE; > - } > - > - num = blk_rq_map_sg(hctx->queue, req, vbr->sg); > - if (num) { > - if (rq_data_dir(req) == WRITE) > - vbr->out_hdr.type |= cpu_to_virtio32(vblk->vdev, VIRTIO_BLK_T_OUT); > - else > - vbr->out_hdr.type |= cpu_to_virtio32(vblk->vdev, VIRTIO_BLK_T_IN); > + num = virtblk_map_data(hctx, req, vbr); > + if (unlikely(num < 0)) { > + virtblk_cleanup_cmd(req); > + return BLK_STS_RESOURCE; > } > > spin_lock_irqsave(&vblk->vqs[qid].lock, flags); > - err = virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg, num); > + err = virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg_table.sgl, num); > if (err) { > virtqueue_kick(vblk->vqs[qid].vq); > /* Don't stop the queue if -ENOMEM: we may have failed to > @@ -303,6 +355,8 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx, > if (err == -ENOSPC) > blk_mq_stop_hw_queue(hctx); > spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags); > + virtblk_unmap_data(req, vbr); > + virtblk_cleanup_cmd(req); > switch (err) { > case -ENOSPC: > return BLK_STS_DEV_RESOURCE; > @@ -681,16 +735,6 @@ static const struct attribute_group *virtblk_attr_groups[] = { > NULL, > }; > > -static int virtblk_init_request(struct blk_mq_tag_set *set, struct request *rq, > - unsigned int hctx_idx, unsigned int numa_node) > -{ > - struct virtio_blk *vblk = set->driver_data; > - struct virtblk_req *vbr = blk_mq_rq_to_pdu(rq); > - > - sg_init_table(vbr->sg, vblk->sg_elems); > - return 0; > -} > - > static int virtblk_map_queues(struct blk_mq_tag_set *set) > { > struct virtio_blk *vblk = set->driver_data; > @@ -703,7 +747,6 @@ 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, > .map_queues = virtblk_map_queues, > }; > > @@ -783,7 +826,7 @@ static int virtblk_probe(struct virtio_device *vdev) > vblk->tag_set.flags = BLK_MQ_F_SHOULD_MERGE; > vblk->tag_set.cmd_size = > sizeof(struct virtblk_req) + > - sizeof(struct scatterlist) * sg_elems; > + sizeof(struct scatterlist) * VIRTIO_BLK_INLINE_SG_CNT; > vblk->tag_set.driver_data = vblk; > vblk->tag_set.nr_hw_queues = vblk->num_vqs; > > -- > 2.18.1 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
[parent not found: <89d6dc30-a876-b1b0-4ff4-605415113611@nvidia.com>]
* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data [not found] ` <89d6dc30-a876-b1b0-4ff4-605415113611@nvidia.com> @ 2021-09-01 15:27 ` Jens Axboe [not found] ` <3ee9405e-733f-30f5-aee2-26b74fbc9cfc@nvidia.com> 0 siblings, 1 reply; 10+ messages in thread From: Jens Axboe @ 2021-09-01 15:27 UTC (permalink / raw) To: Max Gurtovoy, Michael S. Tsirkin Cc: linux-block, kvm, israelr, virtualization, hch, nitzanc, stefanha, oren On 9/1/21 8:58 AM, Max Gurtovoy wrote: > > On 9/1/2021 5:50 PM, Michael S. Tsirkin wrote: >> On Wed, Sep 01, 2021 at 04:14:34PM +0300, Max Gurtovoy wrote: >>> No need to pre-allocate a big buffer for the IO SGL anymore. If a device >>> has lots of deep queues, preallocation for the sg list can consume >>> substantial amounts of memory. For HW virtio-blk device, nr_hw_queues >>> can be 64 or 128 and each queue's depth might be 128. This means the >>> resulting preallocation for the data SGLs is big. >>> >>> Switch to runtime allocation for SGL for lists longer than 2 entries. >>> This is the approach used by NVMe drivers so it should be reasonable for >>> virtio block as well. Runtime SGL allocation has always been the case >>> for the legacy I/O path so this is nothing new. >>> >>> The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't >>> support SG_CHAIN, use only runtime allocation for the SGL. >>> >>> Re-organize the setup of the IO request to fit the new sg chain >>> mechanism. >>> >>> No performance degradation was seen (fio libaio engine with 16 jobs and >>> 128 iodepth): >>> >>> IO size IOPs Rand Read (before/after) IOPs Rand Write (before/after) >>> -------- --------------------------------- ---------------------------------- >>> 512B 318K/316K 329K/325K >>> >>> 4KB 323K/321K 353K/349K >>> >>> 16KB 199K/208K 250K/275K >>> >>> 128KB 36K/36.1K 39.2K/41.7K >>> >>> Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com> >>> Reviewed-by: Israel Rukshin <israelr@nvidia.com> >> Could you use something to give confidence intervals maybe? >> As it is it looks like a 1-2% regression for 512B and 4KB. > > 1%-2% is not a regression. It's a device/env/test variance. > > This is just one test results. I run it many times and got difference by > +/- 2%-3% in each run for each sides. > > Even if I run same driver without changes I get 2%-3% difference between > runs. > > If you have a perf test suite for virtio-blk it will be great if you can > run it, or maybe Feng Li has. You're adding an allocation to the hot path, and a free to the completion hot path. It's not unreasonable to expect that there could be performance implications associated with that. Which would be particularly evident with 1 segment requests, as the results would seem to indicate as well. Probably needs better testing. A profile of a peak run before and after and a diff of the two might also be interesting. The common idiom for situations like this is to have an inline part that holds 1-2 segments, and then only punt to alloc if you need more than that. As the number of segments grows, the cost per request matters less. -- Jens Axboe _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
[parent not found: <3ee9405e-733f-30f5-aee2-26b74fbc9cfc@nvidia.com>]
* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data [not found] ` <3ee9405e-733f-30f5-aee2-26b74fbc9cfc@nvidia.com> @ 2021-09-02 2:08 ` Jens Axboe 0 siblings, 0 replies; 10+ messages in thread From: Jens Axboe @ 2021-09-02 2:08 UTC (permalink / raw) To: Max Gurtovoy, Michael S. Tsirkin Cc: linux-block, kvm, israelr, virtualization, hch, nitzanc, stefanha, oren On 9/1/21 4:25 PM, Max Gurtovoy wrote: > > On 9/1/2021 6:27 PM, Jens Axboe wrote: >> On 9/1/21 8:58 AM, Max Gurtovoy wrote: >>> On 9/1/2021 5:50 PM, Michael S. Tsirkin wrote: >>>> On Wed, Sep 01, 2021 at 04:14:34PM +0300, Max Gurtovoy wrote: >>>>> No need to pre-allocate a big buffer for the IO SGL anymore. If a device >>>>> has lots of deep queues, preallocation for the sg list can consume >>>>> substantial amounts of memory. For HW virtio-blk device, nr_hw_queues >>>>> can be 64 or 128 and each queue's depth might be 128. This means the >>>>> resulting preallocation for the data SGLs is big. >>>>> >>>>> Switch to runtime allocation for SGL for lists longer than 2 entries. >>>>> This is the approach used by NVMe drivers so it should be reasonable for >>>>> virtio block as well. Runtime SGL allocation has always been the case >>>>> for the legacy I/O path so this is nothing new. >>>>> >>>>> The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't >>>>> support SG_CHAIN, use only runtime allocation for the SGL. >>>>> >>>>> Re-organize the setup of the IO request to fit the new sg chain >>>>> mechanism. >>>>> >>>>> No performance degradation was seen (fio libaio engine with 16 jobs and >>>>> 128 iodepth): >>>>> >>>>> IO size IOPs Rand Read (before/after) IOPs Rand Write (before/after) >>>>> -------- --------------------------------- ---------------------------------- >>>>> 512B 318K/316K 329K/325K >>>>> >>>>> 4KB 323K/321K 353K/349K >>>>> >>>>> 16KB 199K/208K 250K/275K >>>>> >>>>> 128KB 36K/36.1K 39.2K/41.7K >>>>> >>>>> Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com> >>>>> Reviewed-by: Israel Rukshin <israelr@nvidia.com> >>>> Could you use something to give confidence intervals maybe? >>>> As it is it looks like a 1-2% regression for 512B and 4KB. >>> 1%-2% is not a regression. It's a device/env/test variance. >>> >>> This is just one test results. I run it many times and got difference by >>> +/- 2%-3% in each run for each sides. >>> >>> Even if I run same driver without changes I get 2%-3% difference between >>> runs. >>> >>> If you have a perf test suite for virtio-blk it will be great if you can >>> run it, or maybe Feng Li has. >> You're adding an allocation to the hot path, and a free to the >> completion hot path. It's not unreasonable to expect that there could be >> performance implications associated with that. Which would be >> particularly evident with 1 segment requests, as the results would seem >> to indicate as well. > > but for sg_nents <= 2 there is no dynamic allocation also in this patch > exactly as we do in nvmf RDMA and FC for example. My quick read missed that, which is why you're using chaining. Then it looks very reasonable to me. >> Probably needs better testing. A profile of a peak run before and after >> and a diff of the two might also be interesting. > > I'll run ezfio test suite with stronger virtio-blk device that reach > > 800KIOPs That'd be better, and preferably a test with pinning etc so that you can show more consistent results. Just reading your table does indeed look like there's a performance degradation, even if you preface it by saying there is none. It would need better explaining, but preferably better testing. >> The common idiom for situations like this is to have an inline part that >> holds 1-2 segments, and then only punt to alloc if you need more than >> that. As the number of segments grows, the cost per request matters >> less. > > isn't this the case here ? or am I missing something ? it totally is, I was the one missing that. -- Jens Axboe _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data [not found] <20210901131434.31158-1-mgurtovoy@nvidia.com> 2021-09-01 14:50 ` [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data Michael S. Tsirkin @ 2021-09-02 12:21 ` Stefan Hajnoczi 2021-09-06 15:09 ` Stefan Hajnoczi 2021-09-27 11:59 ` Christoph Hellwig 3 siblings, 0 replies; 10+ messages in thread From: Stefan Hajnoczi @ 2021-09-02 12:21 UTC (permalink / raw) To: Max Gurtovoy Cc: axboe, linux-block, kvm, mst, israelr, virtualization, hch, nitzanc, oren [-- Attachment #1.1: Type: text/plain, Size: 2254 bytes --] On Wed, Sep 01, 2021 at 04:14:34PM +0300, Max Gurtovoy wrote: > No need to pre-allocate a big buffer for the IO SGL anymore. If a device > has lots of deep queues, preallocation for the sg list can consume > substantial amounts of memory. For HW virtio-blk device, nr_hw_queues > can be 64 or 128 and each queue's depth might be 128. This means the > resulting preallocation for the data SGLs is big. > > Switch to runtime allocation for SGL for lists longer than 2 entries. > This is the approach used by NVMe drivers so it should be reasonable for > virtio block as well. Runtime SGL allocation has always been the case > for the legacy I/O path so this is nothing new. > > The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't > support SG_CHAIN, use only runtime allocation for the SGL. > > Re-organize the setup of the IO request to fit the new sg chain > mechanism. > > No performance degradation was seen (fio libaio engine with 16 jobs and > 128 iodepth): > > IO size IOPs Rand Read (before/after) IOPs Rand Write (before/after) > -------- --------------------------------- ---------------------------------- > 512B 318K/316K 329K/325K > > 4KB 323K/321K 353K/349K > > 16KB 199K/208K 250K/275K > > 128KB 36K/36.1K 39.2K/41.7K > > Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com> > Reviewed-by: Israel Rukshin <israelr@nvidia.com> > --- > > changes from V2: > - initialize vbr->out_hdr.sector during virtblk_setup_cmd > > changes from V1: > - Kconfig update (from Christoph) > - Re-order cmd setup (from Christoph) > - use flexible sg pointer in the cmd (from Christoph) > - added perf numbers to commit msg (from Feng Li) > > --- > drivers/block/Kconfig | 1 + > drivers/block/virtio_blk.c | 155 +++++++++++++++++++++++-------------- > 2 files changed, 100 insertions(+), 56 deletions(-) Hi Max, I can run benchmark to give everyone more confidence about this change. Should I test this version or are you still planning to make code changes? Stefan [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 488 bytes --] [-- Attachment #2: Type: text/plain, Size: 183 bytes --] _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data [not found] <20210901131434.31158-1-mgurtovoy@nvidia.com> 2021-09-01 14:50 ` [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data Michael S. Tsirkin 2021-09-02 12:21 ` Stefan Hajnoczi @ 2021-09-06 15:09 ` Stefan Hajnoczi 2021-09-10 6:32 ` Feng Li [not found] ` <692f8e81-8585-1d39-e7a4-576ae01438a1@nvidia.com> 2021-09-27 11:59 ` Christoph Hellwig 3 siblings, 2 replies; 10+ messages in thread From: Stefan Hajnoczi @ 2021-09-06 15:09 UTC (permalink / raw) To: Max Gurtovoy Cc: axboe, linux-block, kvm, mst, israelr, virtualization, hch, nitzanc, oren [-- Attachment #1.1: Type: text/plain, Size: 2325 bytes --] On Wed, Sep 01, 2021 at 04:14:34PM +0300, Max Gurtovoy wrote: > No need to pre-allocate a big buffer for the IO SGL anymore. If a device > has lots of deep queues, preallocation for the sg list can consume > substantial amounts of memory. For HW virtio-blk device, nr_hw_queues > can be 64 or 128 and each queue's depth might be 128. This means the > resulting preallocation for the data SGLs is big. > > Switch to runtime allocation for SGL for lists longer than 2 entries. > This is the approach used by NVMe drivers so it should be reasonable for > virtio block as well. Runtime SGL allocation has always been the case > for the legacy I/O path so this is nothing new. > > The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't > support SG_CHAIN, use only runtime allocation for the SGL. > > Re-organize the setup of the IO request to fit the new sg chain > mechanism. > > No performance degradation was seen (fio libaio engine with 16 jobs and > 128 iodepth): > > IO size IOPs Rand Read (before/after) IOPs Rand Write (before/after) > -------- --------------------------------- ---------------------------------- > 512B 318K/316K 329K/325K > > 4KB 323K/321K 353K/349K > > 16KB 199K/208K 250K/275K > > 128KB 36K/36.1K 39.2K/41.7K I ran fio randread benchmarks with 4k, 16k, 64k, and 128k at iodepth 1, 8, and 64 on two vCPUs. The results look fine, there is no significant regression. iodepth=1 and iodepth=64 are very consistent. For some reason the iodepth=8 has significant variance but I don't think it's the fault of this patch. Fio results and the Jupyter notebook export are available here (check out benchmark.html to see the graphs): https://gitlab.com/stefanha/virt-playbooks/-/tree/virtio-blk-sgl-allocation-benchmark/notebook Guest: - Fedora 34 - Linux v5.14 - 2 vCPUs (pinned), 4 GB RAM (single host NUMA node) - 1 IOThread (pinned) - virtio-blk aio=native,cache=none,format=raw - QEMU 6.1.0 Host: - RHEL 8.3 - Linux 4.18.0-240.22.1.el8_3.x86_64 - Intel(R) Xeon(R) Silver 4214 CPU @ 2.20GHz - Intel Optane DC P4800X Stefan [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 488 bytes --] [-- Attachment #2: Type: text/plain, Size: 183 bytes --] _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data 2021-09-06 15:09 ` Stefan Hajnoczi @ 2021-09-10 6:32 ` Feng Li [not found] ` <692f8e81-8585-1d39-e7a4-576ae01438a1@nvidia.com> 1 sibling, 0 replies; 10+ messages in thread From: Feng Li @ 2021-09-10 6:32 UTC (permalink / raw) To: Stefan Hajnoczi Cc: Max Gurtovoy, linux-block, kvm, mst, israelr, virtualization, hch, nitzanc, Jens Axboe, oren On Mon, Sep 6, 2021 at 11:39 PM Stefan Hajnoczi <stefanha@redhat.com> wrote: > > On Wed, Sep 01, 2021 at 04:14:34PM +0300, Max Gurtovoy wrote: > > No need to pre-allocate a big buffer for the IO SGL anymore. If a device > > has lots of deep queues, preallocation for the sg list can consume > > substantial amounts of memory. For HW virtio-blk device, nr_hw_queues > > can be 64 or 128 and each queue's depth might be 128. This means the > > resulting preallocation for the data SGLs is big. > > > > Switch to runtime allocation for SGL for lists longer than 2 entries. > > This is the approach used by NVMe drivers so it should be reasonable for > > virtio block as well. Runtime SGL allocation has always been the case > > for the legacy I/O path so this is nothing new. > > > > The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't > > support SG_CHAIN, use only runtime allocation for the SGL. > > > > Re-organize the setup of the IO request to fit the new sg chain > > mechanism. > > > > No performance degradation was seen (fio libaio engine with 16 jobs and > > 128 iodepth): > > > > IO size IOPs Rand Read (before/after) IOPs Rand Write (before/after) > > -------- --------------------------------- ---------------------------------- > > 512B 318K/316K 329K/325K > > > > 4KB 323K/321K 353K/349K > > > > 16KB 199K/208K 250K/275K > > > > 128KB 36K/36.1K 39.2K/41.7K > > I ran fio randread benchmarks with 4k, 16k, 64k, and 128k at iodepth 1, > 8, and 64 on two vCPUs. The results look fine, there is no significant > regression. > > iodepth=1 and iodepth=64 are very consistent. For some reason the > iodepth=8 has significant variance but I don't think it's the fault of > this patch. > > Fio results and the Jupyter notebook export are available here (check > out benchmark.html to see the graphs): > > https://gitlab.com/stefanha/virt-playbooks/-/tree/virtio-blk-sgl-allocation-benchmark/notebook > > Guest: > - Fedora 34 > - Linux v5.14 > - 2 vCPUs (pinned), 4 GB RAM (single host NUMA node) > - 1 IOThread (pinned) > - virtio-blk aio=native,cache=none,format=raw > - QEMU 6.1.0 > > Host: > - RHEL 8.3 > - Linux 4.18.0-240.22.1.el8_3.x86_64 > - Intel(R) Xeon(R) Silver 4214 CPU @ 2.20GHz > - Intel Optane DC P4800X > > Stefan Reviewed-by: Feng Li <lifeng1519@gmail.com> _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
[parent not found: <692f8e81-8585-1d39-e7a4-576ae01438a1@nvidia.com>]
* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data [not found] ` <692f8e81-8585-1d39-e7a4-576ae01438a1@nvidia.com> @ 2021-09-14 12:22 ` Stefan Hajnoczi [not found] ` <56cf84e2-fec0-08e8-0a47-24bb1df71883@nvidia.com> 0 siblings, 1 reply; 10+ messages in thread From: Stefan Hajnoczi @ 2021-09-14 12:22 UTC (permalink / raw) To: Max Gurtovoy Cc: axboe, linux-block, kvm, mst, israelr, virtualization, hch, nitzanc, oren [-- Attachment #1.1: Type: text/plain, Size: 2951 bytes --] On Mon, Sep 13, 2021 at 05:50:21PM +0300, Max Gurtovoy wrote: > > On 9/6/2021 6:09 PM, Stefan Hajnoczi wrote: > > On Wed, Sep 01, 2021 at 04:14:34PM +0300, Max Gurtovoy wrote: > > > No need to pre-allocate a big buffer for the IO SGL anymore. If a device > > > has lots of deep queues, preallocation for the sg list can consume > > > substantial amounts of memory. For HW virtio-blk device, nr_hw_queues > > > can be 64 or 128 and each queue's depth might be 128. This means the > > > resulting preallocation for the data SGLs is big. > > > > > > Switch to runtime allocation for SGL for lists longer than 2 entries. > > > This is the approach used by NVMe drivers so it should be reasonable for > > > virtio block as well. Runtime SGL allocation has always been the case > > > for the legacy I/O path so this is nothing new. > > > > > > The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't > > > support SG_CHAIN, use only runtime allocation for the SGL. > > > > > > Re-organize the setup of the IO request to fit the new sg chain > > > mechanism. > > > > > > No performance degradation was seen (fio libaio engine with 16 jobs and > > > 128 iodepth): > > > > > > IO size IOPs Rand Read (before/after) IOPs Rand Write (before/after) > > > -------- --------------------------------- ---------------------------------- > > > 512B 318K/316K 329K/325K > > > > > > 4KB 323K/321K 353K/349K > > > > > > 16KB 199K/208K 250K/275K > > > > > > 128KB 36K/36.1K 39.2K/41.7K > > I ran fio randread benchmarks with 4k, 16k, 64k, and 128k at iodepth 1, > > 8, and 64 on two vCPUs. The results look fine, there is no significant > > regression. > > > > iodepth=1 and iodepth=64 are very consistent. For some reason the > > iodepth=8 has significant variance but I don't think it's the fault of > > this patch. > > > > Fio results and the Jupyter notebook export are available here (check > > out benchmark.html to see the graphs): > > > > https://gitlab.com/stefanha/virt-playbooks/-/tree/virtio-blk-sgl-allocation-benchmark/notebook > > > > Guest: > > - Fedora 34 > > - Linux v5.14 > > - 2 vCPUs (pinned), 4 GB RAM (single host NUMA node) > > - 1 IOThread (pinned) > > - virtio-blk aio=native,cache=none,format=raw > > - QEMU 6.1.0 > > > > Host: > > - RHEL 8.3 > > - Linux 4.18.0-240.22.1.el8_3.x86_64 > > - Intel(R) Xeon(R) Silver 4214 CPU @ 2.20GHz > > - Intel Optane DC P4800X > > > > Stefan > > Thanks, Stefan. > > Would you like me to add some of the results in my commit msg ? or Tested-By > sign ? Thanks, there's no need to change the commit description. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Tested-by: Stefan Hajnoczi <stefanha@redhat.com> [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 488 bytes --] [-- Attachment #2: Type: text/plain, Size: 183 bytes --] _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
[parent not found: <56cf84e2-fec0-08e8-0a47-24bb1df71883@nvidia.com>]
* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data [not found] ` <56cf84e2-fec0-08e8-0a47-24bb1df71883@nvidia.com> @ 2021-09-23 15:37 ` Michael S. Tsirkin 2021-10-22 9:15 ` Michael S. Tsirkin 1 sibling, 0 replies; 10+ messages in thread From: Michael S. Tsirkin @ 2021-09-23 15:37 UTC (permalink / raw) To: Max Gurtovoy Cc: Jens Axboe, linux-block, kvm, israelr, virtualization, hch, nitzanc, Stefan Hajnoczi, oren OK by me. Acked-by: Michael S. Tsirkin <mst@redhat.com> I will queue it for the next kernel. Thanks! On Thu, Sep 23, 2021 at 04:40:56PM +0300, Max Gurtovoy wrote: > Hi MST/Jens, > > Do we need more review here or are we ok with the code and the test matrix ? > > If we're ok, we need to decide if this goes through virtio PR or block PR. > > Cheers, > > -Max. > > On 9/14/2021 3:22 PM, Stefan Hajnoczi wrote: > > On Mon, Sep 13, 2021 at 05:50:21PM +0300, Max Gurtovoy wrote: > > > On 9/6/2021 6:09 PM, Stefan Hajnoczi wrote: > > > > On Wed, Sep 01, 2021 at 04:14:34PM +0300, Max Gurtovoy wrote: > > > > > No need to pre-allocate a big buffer for the IO SGL anymore. If a device > > > > > has lots of deep queues, preallocation for the sg list can consume > > > > > substantial amounts of memory. For HW virtio-blk device, nr_hw_queues > > > > > can be 64 or 128 and each queue's depth might be 128. This means the > > > > > resulting preallocation for the data SGLs is big. > > > > > > > > > > Switch to runtime allocation for SGL for lists longer than 2 entries. > > > > > This is the approach used by NVMe drivers so it should be reasonable for > > > > > virtio block as well. Runtime SGL allocation has always been the case > > > > > for the legacy I/O path so this is nothing new. > > > > > > > > > > The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't > > > > > support SG_CHAIN, use only runtime allocation for the SGL. > > > > > > > > > > Re-organize the setup of the IO request to fit the new sg chain > > > > > mechanism. > > > > > > > > > > No performance degradation was seen (fio libaio engine with 16 jobs and > > > > > 128 iodepth): > > > > > > > > > > IO size IOPs Rand Read (before/after) IOPs Rand Write (before/after) > > > > > -------- --------------------------------- ---------------------------------- > > > > > 512B 318K/316K 329K/325K > > > > > > > > > > 4KB 323K/321K 353K/349K > > > > > > > > > > 16KB 199K/208K 250K/275K > > > > > > > > > > 128KB 36K/36.1K 39.2K/41.7K > > > > I ran fio randread benchmarks with 4k, 16k, 64k, and 128k at iodepth 1, > > > > 8, and 64 on two vCPUs. The results look fine, there is no significant > > > > regression. > > > > > > > > iodepth=1 and iodepth=64 are very consistent. For some reason the > > > > iodepth=8 has significant variance but I don't think it's the fault of > > > > this patch. > > > > > > > > Fio results and the Jupyter notebook export are available here (check > > > > out benchmark.html to see the graphs): > > > > > > > > https://gitlab.com/stefanha/virt-playbooks/-/tree/virtio-blk-sgl-allocation-benchmark/notebook > > > > > > > > Guest: > > > > - Fedora 34 > > > > - Linux v5.14 > > > > - 2 vCPUs (pinned), 4 GB RAM (single host NUMA node) > > > > - 1 IOThread (pinned) > > > > - virtio-blk aio=native,cache=none,format=raw > > > > - QEMU 6.1.0 > > > > > > > > Host: > > > > - RHEL 8.3 > > > > - Linux 4.18.0-240.22.1.el8_3.x86_64 > > > > - Intel(R) Xeon(R) Silver 4214 CPU @ 2.20GHz > > > > - Intel Optane DC P4800X > > > > > > > > Stefan > > > Thanks, Stefan. > > > > > > Would you like me to add some of the results in my commit msg ? or Tested-By > > > sign ? > > Thanks, there's no need to change the commit description. > > > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > > Tested-by: Stefan Hajnoczi <stefanha@redhat.com> _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data [not found] ` <56cf84e2-fec0-08e8-0a47-24bb1df71883@nvidia.com> 2021-09-23 15:37 ` Michael S. Tsirkin @ 2021-10-22 9:15 ` Michael S. Tsirkin 1 sibling, 0 replies; 10+ messages in thread From: Michael S. Tsirkin @ 2021-10-22 9:15 UTC (permalink / raw) To: Max Gurtovoy Cc: Jens Axboe, linux-block, kvm, israelr, virtualization, hch, nitzanc, Stefan Hajnoczi, oren My tree is ok. Looks like your patch was developed on top of some other tree, not plan upstream linux, so git am fails. I applied it using patch and some manual tweaking, and it seems to work for me but please do test it in linux-next and confirm - will push to a linux-next branch in my tree soon. On Thu, Sep 23, 2021 at 04:40:56PM +0300, Max Gurtovoy wrote: > Hi MST/Jens, > > Do we need more review here or are we ok with the code and the test matrix ? > > If we're ok, we need to decide if this goes through virtio PR or block PR. > > Cheers, > > -Max. > > On 9/14/2021 3:22 PM, Stefan Hajnoczi wrote: > > On Mon, Sep 13, 2021 at 05:50:21PM +0300, Max Gurtovoy wrote: > > > On 9/6/2021 6:09 PM, Stefan Hajnoczi wrote: > > > > On Wed, Sep 01, 2021 at 04:14:34PM +0300, Max Gurtovoy wrote: > > > > > No need to pre-allocate a big buffer for the IO SGL anymore. If a device > > > > > has lots of deep queues, preallocation for the sg list can consume > > > > > substantial amounts of memory. For HW virtio-blk device, nr_hw_queues > > > > > can be 64 or 128 and each queue's depth might be 128. This means the > > > > > resulting preallocation for the data SGLs is big. > > > > > > > > > > Switch to runtime allocation for SGL for lists longer than 2 entries. > > > > > This is the approach used by NVMe drivers so it should be reasonable for > > > > > virtio block as well. Runtime SGL allocation has always been the case > > > > > for the legacy I/O path so this is nothing new. > > > > > > > > > > The preallocated small SGL depends on SG_CHAIN so if the ARCH doesn't > > > > > support SG_CHAIN, use only runtime allocation for the SGL. > > > > > > > > > > Re-organize the setup of the IO request to fit the new sg chain > > > > > mechanism. > > > > > > > > > > No performance degradation was seen (fio libaio engine with 16 jobs and > > > > > 128 iodepth): > > > > > > > > > > IO size IOPs Rand Read (before/after) IOPs Rand Write (before/after) > > > > > -------- --------------------------------- ---------------------------------- > > > > > 512B 318K/316K 329K/325K > > > > > > > > > > 4KB 323K/321K 353K/349K > > > > > > > > > > 16KB 199K/208K 250K/275K > > > > > > > > > > 128KB 36K/36.1K 39.2K/41.7K > > > > I ran fio randread benchmarks with 4k, 16k, 64k, and 128k at iodepth 1, > > > > 8, and 64 on two vCPUs. The results look fine, there is no significant > > > > regression. > > > > > > > > iodepth=1 and iodepth=64 are very consistent. For some reason the > > > > iodepth=8 has significant variance but I don't think it's the fault of > > > > this patch. > > > > > > > > Fio results and the Jupyter notebook export are available here (check > > > > out benchmark.html to see the graphs): > > > > > > > > https://gitlab.com/stefanha/virt-playbooks/-/tree/virtio-blk-sgl-allocation-benchmark/notebook > > > > > > > > Guest: > > > > - Fedora 34 > > > > - Linux v5.14 > > > > - 2 vCPUs (pinned), 4 GB RAM (single host NUMA node) > > > > - 1 IOThread (pinned) > > > > - virtio-blk aio=native,cache=none,format=raw > > > > - QEMU 6.1.0 > > > > > > > > Host: > > > > - RHEL 8.3 > > > > - Linux 4.18.0-240.22.1.el8_3.x86_64 > > > > - Intel(R) Xeon(R) Silver 4214 CPU @ 2.20GHz > > > > - Intel Optane DC P4800X > > > > > > > > Stefan > > > Thanks, Stefan. > > > > > > Would you like me to add some of the results in my commit msg ? or Tested-By > > > sign ? > > Thanks, there's no need to change the commit description. > > > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > > Tested-by: Stefan Hajnoczi <stefanha@redhat.com> _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data [not found] <20210901131434.31158-1-mgurtovoy@nvidia.com> ` (2 preceding siblings ...) 2021-09-06 15:09 ` Stefan Hajnoczi @ 2021-09-27 11:59 ` Christoph Hellwig 3 siblings, 0 replies; 10+ messages in thread From: Christoph Hellwig @ 2021-09-27 11:59 UTC (permalink / raw) To: Max Gurtovoy Cc: axboe, linux-block, kvm, mst, israelr, virtualization, hch, nitzanc, stefanha, oren Looks good, Reviewed-by: Christoph Hellwig <hch@lst.de> _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2021-10-22 9:16 UTC | newest] Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- [not found] <20210901131434.31158-1-mgurtovoy@nvidia.com> 2021-09-01 14:50 ` [PATCH v3 1/1] virtio-blk: avoid preallocating big SGL for data Michael S. Tsirkin [not found] ` <89d6dc30-a876-b1b0-4ff4-605415113611@nvidia.com> 2021-09-01 15:27 ` Jens Axboe [not found] ` <3ee9405e-733f-30f5-aee2-26b74fbc9cfc@nvidia.com> 2021-09-02 2:08 ` Jens Axboe 2021-09-02 12:21 ` Stefan Hajnoczi 2021-09-06 15:09 ` Stefan Hajnoczi 2021-09-10 6:32 ` Feng Li [not found] ` <692f8e81-8585-1d39-e7a4-576ae01438a1@nvidia.com> 2021-09-14 12:22 ` Stefan Hajnoczi [not found] ` <56cf84e2-fec0-08e8-0a47-24bb1df71883@nvidia.com> 2021-09-23 15:37 ` Michael S. Tsirkin 2021-10-22 9:15 ` Michael S. Tsirkin 2021-09-27 11:59 ` Christoph Hellwig
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).