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iser-target: Avoid using FRMR for single dma entry requests 

This patch changes isert_reg_rdma_frwr() to not use FRMR for single
dma entry requests from small I/Os, in order to avoid the associated
memory registration overhead.

Using DMA MR is sufficient here for the single dma entry requests,
and addresses a >= v3.12 performance regression.

Signed-off-by: Vu Pham <vu@mellanox.com>
Cc: <stable@vger.kernel.org> # v3.12+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Vu Pham 2013-11-11 19:04:29 +02:00 committed by Nicholas Bellinger
parent 4863e52565
commit f01b9f7339
1 changed files with 19 additions and 11 deletions
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8
drivers/infiniband/ulp/isert/ib_isert.c
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@ -2297,6 +2297,13 @@ isert_reg_rdma_frwr(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
data_len = min(data_left, rdma_write_max); data_len = min(data_left, rdma_write_max);
wr->cur_rdma_length = data_len; wr->cur_rdma_length = data_len;
/* if there is a single dma entry, dma mr is sufficient */
if (count == 1) {
ib_sge->addr = ib_sg_dma_address(ib_dev, &sg_start[0]);
ib_sge->length = ib_sg_dma_len(ib_dev, &sg_start[0]);
ib_sge->lkey = isert_conn->conn_mr->lkey;
wr->fr_desc = NULL;
} else {
spin_lock_irqsave(&isert_conn->conn_lock, flags); spin_lock_irqsave(&isert_conn->conn_lock, flags);
fr_desc = list_first_entry(&isert_conn->conn_frwr_pool, fr_desc = list_first_entry(&isert_conn->conn_frwr_pool,
struct fast_reg_descriptor, list); struct fast_reg_descriptor, list);
@ -2310,6 +2317,7 @@ isert_reg_rdma_frwr(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
list_add_tail(&fr_desc->list, &isert_conn->conn_frwr_pool); list_add_tail(&fr_desc->list, &isert_conn->conn_frwr_pool);
goto unmap_sg; goto unmap_sg;
} }
}
return 0; return 0;