[PATCH v3 2/3] nvme-rdma: support up to 4 segments of inline data

[swise@opengridcomputing.com (Steve Wise)]

Hey Sagi,


On 5/30/2018 4:42 PM, Sagi Grimberg wrote:
>
>
> On 05/29/2018 09:25 PM, Steve Wise wrote:
>> Allow up to 4 segments of inline data for NVMF WRITE operations. This
>> reduces latency for small WRITEs by removing the need for the target to
>> issue a READ WR for IB, or a REG_MR + READ WR chain for iWarp.
>>
>> Also cap the inline segments used based on the limitations of the
>> device.
>>
>> Signed-off-by: Steve Wise <swise at opengridcomputing.com>
>> Reviewed-by: Christoph Hellwig <hch at lst.de>
>> ---
>> ? drivers/nvme/host/rdma.c | 39 ++++++++++++++++++++++++++++-----------
>> ? 1 file changed, 28 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
>> index f11faa8..32d2f4c 100644
>> --- a/drivers/nvme/host/rdma.c
>> +++ b/drivers/nvme/host/rdma.c
>> @@ -40,13 +40,14 @@
>> ? ? #define NVME_RDMA_MAX_SEGMENTS??????? 256
>> ? -#define NVME_RDMA_MAX_INLINE_SEGMENTS??? 1
>> +#define NVME_RDMA_MAX_INLINE_SEGMENTS??? 4
>> ? ? struct nvme_rdma_device {
>> ????? struct ib_device??? *dev;
>> ????? struct ib_pd??????? *pd;
>> ????? struct kref??????? ref;
>> ????? struct list_head??? entry;
>> +??? unsigned int??????? num_inline_segments;
>> ? };
>> ? ? struct nvme_rdma_qe {
>> @@ -117,6 +118,7 @@ struct nvme_rdma_ctrl {
>> ????? struct sockaddr_storage src_addr;
>> ? ????? struct nvme_ctrl??? ctrl;
>> +??? bool??????????? use_inline_data;
>> ? };
>> ? ? static inline struct nvme_rdma_ctrl *to_rdma_ctrl(struct
>> nvme_ctrl *ctrl)
>> @@ -249,7 +251,7 @@ static int nvme_rdma_create_qp(struct
>> nvme_rdma_queue *queue, const int factor)
>> ????? /* +1 for drain */
>> ????? init_attr.cap.max_recv_wr = queue->queue_size + 1;
>> ????? init_attr.cap.max_recv_sge = 1;
>> -??? init_attr.cap.max_send_sge = 1 + NVME_RDMA_MAX_INLINE_SEGMENTS;
>> +??? init_attr.cap.max_send_sge = 1 + dev->num_inline_segments;
>> ????? init_attr.sq_sig_type = IB_SIGNAL_REQ_WR;
>> ????? init_attr.qp_type = IB_QPT_RC;
>> ????? init_attr.send_cq = queue->ib_cq;
>> @@ -374,6 +376,9 @@ static int nvme_rdma_dev_get(struct
>> nvme_rdma_device *dev)
>> ????????? goto out_free_pd;
>> ????? }
>> ? +??? ndev->num_inline_segments = min(NVME_RDMA_MAX_INLINE_SEGMENTS,
>> +??????????????????? ndev->dev->attrs.max_sge - 1);
>> +??? pr_debug("num_inline_segments = %u\n", ndev->num_inline_segments);
>
> insist on keeping it? ibv_devinfo -v can give this info to the
> user/developer.
>

I agree.? I'll remove it.?

>> ????? list_add(&ndev->entry, &device_list);
>> ? out_unlock:
>> ????? mutex_unlock(&device_list_mutex);
>> @@ -1086,19 +1091,27 @@ static int nvme_rdma_set_sg_null(struct
>> nvme_command *c)
>> ? }
>> ? ? static int nvme_rdma_map_sg_inline(struct nvme_rdma_queue *queue,
>> -??????? struct nvme_rdma_request *req, struct nvme_command *c)
>> +??????? struct nvme_rdma_request *req, struct nvme_command *c,
>> +??????? int count)
>> ? {
>> ????? struct nvme_sgl_desc *sg = &c->common.dptr.sgl;
>> +??? struct scatterlist *sgl = req->sg_table.sgl;
>> +??? struct ib_sge *sge = &req->sge[1];
>> +??? u32 len = 0;
>> +??? int i;
>> ? -??? req->sge[1].addr = sg_dma_address(req->sg_table.sgl);
>> -??? req->sge[1].length = sg_dma_len(req->sg_table.sgl);
>> -??? req->sge[1].lkey = queue->device->pd->local_dma_lkey;
>> +??? for (i = 0; i < count; i++, sgl++, sge++) {
>> +??????? sge->addr = sg_dma_address(sgl);
>> +??????? sge->length = sg_dma_len(sgl);
>> +??????? sge->lkey = queue->device->pd->local_dma_lkey;
>> +??????? len += sge->length;
>> +??? }
>> ? ????? sg->addr = cpu_to_le64(queue->ctrl->ctrl.icdoff);
>> -??? sg->length = cpu_to_le32(sg_dma_len(req->sg_table.sgl));
>> +??? sg->length = cpu_to_le32(len);
>> ????? sg->type = (NVME_SGL_FMT_DATA_DESC << 4) | NVME_SGL_FMT_OFFSET;
>> ? -??? req->num_sge++;
>> +??? req->num_sge += count;
>> ????? return 0;
>> ? }
>> ? @@ -1191,13 +1204,14 @@ static int nvme_rdma_map_data(struct
>> nvme_rdma_queue *queue,
>> ????????? return -EIO;
>> ????? }
>> ? -??? if (count == 1) {
>> +??? if (count <= dev->num_inline_segments) {
>> ????????? if (rq_data_dir(rq) == WRITE && nvme_rdma_queue_idx(queue) &&
>> +??????????? queue->ctrl->use_inline_data &&
>> ????????????? blk_rq_payload_bytes(rq) <=
>> ????????????????? nvme_rdma_inline_data_size(queue))
>> -??????????? return nvme_rdma_map_sg_inline(queue, req, c);
>> +??????????? return nvme_rdma_map_sg_inline(queue, req, c, count);
>> ? -??????? if (dev->pd->flags & IB_PD_UNSAFE_GLOBAL_RKEY)
>> +??????? if (count == 1 && dev->pd->flags & IB_PD_UNSAFE_GLOBAL_RKEY)
>> ????????????? return nvme_rdma_map_sg_single(queue, req, c);
>> ????? }
>> ? @@ -1955,6 +1969,9 @@ static struct nvme_ctrl
>> *nvme_rdma_create_ctrl(struct device *dev,
>> ????????? goto out_remove_admin_queue;
>> ????? }
>> ? +??? if ((ctrl->ctrl.sgls & (1 << 20)))
>> +??????? ctrl->use_inline_data = true;
>> +
>
> Here it is... discard my last comment.