From: Jenny Derzhavetz <jennyf@xxxxxxxxxxxx>
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 <jennyf@xxxxxxxxxxxx>
Signed-off-by: Sagi Grimberg <sagig@xxxxxxxxxxxx>
---
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 f0d7e0c6d936..cb4b00769add 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -1328,9 +1328,9 @@ 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)
@@ -1339,7 +1339,10 @@ 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;
@@ -1351,13 +1354,20 @@ 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 c905e90d673c..afb62786c431 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;
--
1.8.4.3
--
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