optimize iser scsi command response processing flow to avoid taking extra
reference on the iscsi task and to use libiscsi lockless completion path.
This way there's no contention on the session lock between the scsi command
submission to the scsi command completion flows.
Signed-off-by: Or Gerlitz <ogerl...@voltaire.com>
-----
Mike, I'd like to get feedback on this approach/patch, basically I'd
to avoid taking the session lock on the command response flow:
- the kfifo_put call is safe since there's one consumer (xmit flow under
lock for passthrough, and xmit worker for non passthrough) and one
producer (response flow has single tasklet instance).
- to my understanding, the _get/put task calls in iser_rcv_completion add
nothing so I removed them
so I think I am left with the updates to session-> max_cmdsn/exp_cmdsn in
__iscsi_update_cmdsn, etc (conn->statsn). Am I correct that this is
the only thing to settle here?
Or.
Index: linux-2.6/drivers/infiniband/ulp/iser/iser_initiator.c
===================================================================
--- linux-2.6.orig/drivers/infiniband/ulp/iser/iser_initiator.c
+++ linux-2.6/drivers/infiniband/ulp/iser/iser_initiator.c
@@ -575,7 +575,7 @@ void iser_rcv_completion(struct iser_des
struct iscsi_iser_task *iser_task;
struct iscsi_hdr *hdr;
char *rx_data = NULL;
- int rx_data_len = 0;
+ int err, rx_data_len = 0;
unsigned char opcode;
hdr = &rx_desc->iscsi_header;
@@ -591,11 +591,7 @@ void iser_rcv_completion(struct iser_des
opcode = hdr->opcode & ISCSI_OPCODE_MASK;
if (opcode == ISCSI_OP_SCSI_CMD_RSP) {
- spin_lock(&conn->iscsi_conn->session->lock);
task = iscsi_itt_to_ctask(conn->iscsi_conn, hdr->itt);
- if (task)
- __iscsi_get_task(task);
- spin_unlock(&conn->iscsi_conn->session->lock);
if (!task)
iser_err("itt can't be matched to task!!! "
@@ -606,12 +602,15 @@ void iser_rcv_completion(struct iser_des
iser_dbg("itt %d task %p\n",hdr->itt, task);
iser_task->status = ISER_TASK_STATUS_COMPLETED;
iser_task_rdma_finalize(iser_task);
- iscsi_put_task(task);
+
+ err = __iscsi_complete_pdu(conn->iscsi_conn, hdr,
+ rx_data, rx_data_len);
}
- }
- iser_dto_buffs_release(dto);
+ } else
+ err = iscsi_complete_pdu(conn->iscsi_conn, hdr,
+ rx_data, rx_data_len);
- iscsi_iser_recv(conn->iscsi_conn, hdr, rx_data, rx_data_len);
+ iser_dto_buffs_release(dto);
kfree(rx_desc->data);
kmem_cache_free(ig.desc_cache, rx_desc);
--
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