The SRP initiator will currently send requests, even if we have no
credits available. The results of sending extra requests is
vendor-specific, but on some devices, overrunning our credits will cost
us 85% of peak performance -- e.g. 100 MB/s vs 720 MB/s. Other devices
may just drop them.
This patch will tell the SCSI mid-layer to queue requests if there are
less than two credits remaining, and will not issue a task management
request if there are no credits remaining. The mid-layer will retry the
queued command once an outstanding command completes.
Also, it adds a queue length parameter to the target options, so that
the maximum number of commands the SCSI mid-layer will try to send can
be capped before it hits the credit limit.
Signed-off-by: David Dillow <[EMAIL PROTECTED]>
---
A cleanup would be to get rid of the zero_req_lim counter, as it should
never be hit now.
ib_srp.c | 49 +++++++++++++++++++++++++++++++++++++++++++------
ib_srp.h | 5 +++++
2 files changed, 48 insertions(+), 6 deletions(-)
diff --git a/drivers/infiniband/ulp/srp/ib_srp.c
b/drivers/infiniband/ulp/srp/ib_srp.c
index 950228f..18dbe89 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -925,6 +925,28 @@ static int srp_post_recv(struct srp_target_port *target)
return ret;
}
+/* Must be called with target->scsi_host->host_lock held to protect
+ * req_lim. Lock cannot be dropped between here and srp_use_credit().
+ */
+static int srp_check_credit(struct srp_target_port *target,
+ enum srp_request_type req_type)
+{
+ /* Each request requires one credit, and we hold a credit in reserve
+ * so that we can send task management requests.
+ */
+ s32 min = (req_type == SRP_REQ_TASK_MGMT) ? 1 : 2;
+ return target->req_lim < min;
+}
+
+/* Must be called with target->scsi_host->host_lock held to protect
+ * req_lim. Lock cannot be dropped between the call to srp_check_credit()
+ * and the call to srp_use_credit()
+ */
+static void srp_use_credit(struct srp_target_port *target)
+{
+ target->req_lim--;
+}
+
/*
* Must be called with target->scsi_host->host_lock held to protect
* req_lim and tx_head. Lock cannot be dropped between call here and
@@ -965,10 +987,8 @@ static int __srp_post_send(struct srp_target_port *target,
ret = ib_post_send(target->qp, &wr, &bad_wr);
- if (!ret) {
+ if (!ret)
++target->tx_head;
- --target->req_lim;
- }
return ret;
}
@@ -993,6 +1013,9 @@ static int srp_queuecommand(struct scsi_cmnd *scmnd,
return 0;
}
+ if (srp_check_credit(target, SRP_REQ_NORMAL))
+ goto err;
+
iu = __srp_get_tx_iu(target);
if (!iu)
goto err;
@@ -1039,6 +1062,8 @@ static int srp_queuecommand(struct scsi_cmnd *scmnd,
goto err_unmap;
}
+ srp_use_credit(target);
+
list_move_tail(&req->list, &target->req_queue);
return 0;
@@ -1180,9 +1205,6 @@ static int srp_cm_handler(struct ib_cm_id *cm_id, struct
ib_cm_event *event)
target->max_ti_iu_len = be32_to_cpu(rsp->max_ti_iu_len);
target->req_lim = be32_to_cpu(rsp->req_lim_delta);
-
- target->scsi_host->can_queue = min(target->req_lim,
-
target->scsi_host->can_queue);
} else {
printk(KERN_WARNING PFX "Unhandled RSP opcode %#x\n",
opcode);
target->status = -ECONNRESET;
@@ -1283,6 +1305,9 @@ static int srp_send_tsk_mgmt(struct srp_target_port
*target,
init_completion(&req->done);
+ if (srp_check_credit(target, SRP_REQ_TASK_MGMT))
+ goto out;
+
iu = __srp_get_tx_iu(target);
if (!iu)
goto out;
@@ -1300,6 +1325,7 @@ static int srp_send_tsk_mgmt(struct srp_target_port
*target,
goto out;
req->tsk_mgmt = iu;
+ srp_use_credit(target);
spin_unlock_irq(target->scsi_host->host_lock);
@@ -1540,6 +1566,7 @@ static struct scsi_host_template srp_template = {
.eh_device_reset_handler = srp_reset_device,
.eh_host_reset_handler = srp_reset_host,
.can_queue = SRP_SQ_SIZE,
+ .max_host_blocked = 1,
.this_id = -1,
.cmd_per_lun = SRP_SQ_SIZE,
.use_clustering = ENABLE_CLUSTERING,
@@ -1610,6 +1637,7 @@ enum {
SRP_OPT_MAX_CMD_PER_LUN = 1 << 6,
SRP_OPT_IO_CLASS = 1 << 7,
SRP_OPT_INITIATOR_EXT = 1 << 8,
+ SRP_OPT_QUEUE_LEN = 1 << 9,
SRP_OPT_ALL = (SRP_OPT_ID_EXT |
SRP_OPT_IOC_GUID |
SRP_OPT_DGID |
@@ -1627,6 +1655,7 @@ static match_table_t srp_opt_tokens = {
{ SRP_OPT_MAX_CMD_PER_LUN, "max_cmd_per_lun=%d" },
{ SRP_OPT_IO_CLASS, "io_class=%x" },
{ SRP_OPT_INITIATOR_EXT, "initiator_ext=%s" },
+ { SRP_OPT_QUEUE_LEN, "queue_len=%d" },
{ SRP_OPT_ERR, NULL }
};
@@ -1754,6 +1783,14 @@ static int srp_parse_options(const char *buf, struct
srp_target_port *target)
kfree(p);
break;
+ case SRP_OPT_QUEUE_LEN:
+ if (match_int(args, &token)) {
+ printk(KERN_WARNING PFX "bad queue_len
parameter '%s'\n", p);
+ goto out;
+ }
+ target->scsi_host->can_queue = min(token, SRP_SQ_SIZE);
+ break;
+
default:
printk(KERN_WARNING PFX "unknown parameter or missing
value "
"'%s' in target creation request\n", p);
diff --git a/drivers/infiniband/ulp/srp/ib_srp.h
b/drivers/infiniband/ulp/srp/ib_srp.h
index e3573e7..4a3c1f3 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -79,6 +79,11 @@ enum srp_target_state {
SRP_TARGET_REMOVED
};
+enum srp_request_type {
+ SRP_REQ_NORMAL,
+ SRP_REQ_TASK_MGMT,
+};
+
struct srp_device {
struct list_head dev_list;
struct ib_device *dev;
_______________________________________________
general mailing list
[email protected]
http://lists.openfabrics.org/cgi-bin/mailman/listinfo/general
To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
