From 9fd60088ffed7573c2d409ddc63a2150a5edd5d8 Mon Sep 17 00:00:00 2001 From: Jenny Derzhavetz Date: Sun, 6 Sep 2015 14:52:26 +0300 Subject: [PATCH] iser-target: Skip data copy if all the command data comes as immediate Given that supporting zcopy immediate data for all IOs requires iser driver to use its own buffer allocations, we settle with avoiding data copy for IOs with data length of up to 8K (which is more latency sensitive anyway). This trims IO write latency by up to 3us and increase IOPs by up to 40% by saving CPU time doing sg_copy_from_buffer (8K IO size is the obvious winner here). Signed-off-by: Jenny Derzhavetz Signed-off-by: Sagi Grimberg Signed-off-by: Nicholas Bellinger --- drivers/infiniband/ulp/isert/ib_isert.c | 26 +++++++++++++++++-------- drivers/infiniband/ulp/isert/ib_isert.h | 1 + 2 files changed, 19 insertions(+), 8 deletions(-) diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c index 233b8c7a78df..aa59037d7504 100644 --- a/drivers/infiniband/ulp/isert/ib_isert.c +++ b/drivers/infiniband/ulp/isert/ib_isert.c @@ -1315,9 +1315,9 @@ isert_handle_scsi_cmd(struct isert_conn *isert_conn, { struct iscsi_conn *conn = isert_conn->conn; struct iscsi_scsi_req *hdr = (struct iscsi_scsi_req *)buf; - struct scatterlist *sg; int imm_data, imm_data_len, unsol_data, sg_nents, rc; bool dump_payload = false; + unsigned int data_len; rc = iscsit_setup_scsi_cmd(conn, cmd, buf); if (rc < 0) @@ -1326,7 +1326,10 @@ isert_handle_scsi_cmd(struct isert_conn *isert_conn, imm_data = cmd->immediate_data; imm_data_len = cmd->first_burst_len; unsol_data = cmd->unsolicited_data; + data_len = cmd->se_cmd.data_length; + if (imm_data && imm_data_len == data_len) + cmd->se_cmd.se_cmd_flags |= SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC; rc = iscsit_process_scsi_cmd(conn, cmd, hdr); if (rc < 0) { return 0; @@ -1338,13 +1341,20 @@ isert_handle_scsi_cmd(struct isert_conn *isert_conn, if (!imm_data) return 0; - sg = &cmd->se_cmd.t_data_sg[0]; - sg_nents = max(1UL, DIV_ROUND_UP(imm_data_len, PAGE_SIZE)); - - isert_dbg("Copying Immediate SG: %p sg_nents: %u from %p imm_data_len: %d\n", - sg, sg_nents, &rx_desc->data[0], imm_data_len); - - sg_copy_from_buffer(sg, sg_nents, &rx_desc->data[0], imm_data_len); + if (imm_data_len != data_len) { + sg_nents = max(1UL, DIV_ROUND_UP(imm_data_len, PAGE_SIZE)); + sg_copy_from_buffer(cmd->se_cmd.t_data_sg, sg_nents, + &rx_desc->data[0], imm_data_len); + isert_dbg("Copy Immediate sg_nents: %u imm_data_len: %d\n", + sg_nents, imm_data_len); + } else { + sg_init_table(&isert_cmd->sg, 1); + cmd->se_cmd.t_data_sg = &isert_cmd->sg; + cmd->se_cmd.t_data_nents = 1; + sg_set_buf(&isert_cmd->sg, &rx_desc->data[0], imm_data_len); + isert_dbg("Transfer Immediate imm_data_len: %d\n", + imm_data_len); + } cmd->write_data_done += imm_data_len; diff --git a/drivers/infiniband/ulp/isert/ib_isert.h b/drivers/infiniband/ulp/isert/ib_isert.h index e586ee1691e9..c5b99bcecbcf 100644 --- a/drivers/infiniband/ulp/isert/ib_isert.h +++ b/drivers/infiniband/ulp/isert/ib_isert.h @@ -139,6 +139,7 @@ struct isert_cmd { struct iser_rx_desc *rx_desc; struct isert_rdma_wr rdma_wr; struct work_struct comp_work; + struct scatterlist sg; }; struct isert_device;