During heavy I/O transmission, it was observed that network packets
can get dropped when no link flow control is enabled. When this happens,
I/O completions can exceed the default NOP transmission of 5s while the
hw send queue resource backs up. When the queue gets full, NOP
transmission requests will also get blocked. It was observed that
the NOP transmission requests will keep repeatedly try to send out
the NOP while holding the session lock. This is very intrusive as the
requests are being called on every timer execution since the last_ping
parameter doesn't get updated upon transmission failure. This creates a
tremendous bottleneck especially when the connection is about to get torn down.
This patch alleviates the pounding of the NOP transmission in the
iscsi_check_transport_timeouts routine by injecting an artifical 1s delay
in between each NOP transmission requests due to failures upon timeout.
There is no need to keep pounding on to request this data provoking NOP
transmission continuously when the transmit queue is full.
Please review and comment. Thanks.
Signed-off-by: Eddie Wai <eddie.wai@xxxxxxxxxxxx>
---
drivers/scsi/libiscsi.c | 13 +++++++++----
1 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 82c3fd4..f1141a8 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -940,13 +940,14 @@ static void iscsi_tmf_rsp(struct iscsi_conn *conn, struct iscsi_hdr *hdr)
wake_up(&conn->ehwait);
}
-static void iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
+static struct iscsi_task *iscsi_send_nopout(struct iscsi_conn *conn,
+ struct iscsi_nopin *rhdr)
{
struct iscsi_nopout hdr;
struct iscsi_task *task;
if (!rhdr && conn->ping_task)
- return;
+ return NULL;
memset(&hdr, 0, sizeof(struct iscsi_nopout));
hdr.opcode = ISCSI_OP_NOOP_OUT | ISCSI_OP_IMMEDIATE;
@@ -967,6 +968,7 @@ static void iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
conn->ping_task = task;
conn->last_ping = jiffies;
}
+ return task;
}
static int iscsi_nop_out_rsp(struct iscsi_task *task,
@@ -2059,8 +2061,11 @@ static void iscsi_check_transport_timeouts(unsigned long data)
if (time_before_eq(last_recv + recv_timeout, jiffies)) {
/* send a ping to try to provoke some traffic */
ISCSI_DBG_CONN(conn, "Sending nopout as ping\n");
- iscsi_send_nopout(conn, NULL);
- next_timeout = conn->last_ping + (conn->ping_timeout * HZ);
+ if (iscsi_send_nopout(conn, NULL))
+ next_timeout = conn->last_ping +
+ (conn->ping_timeout * HZ);
+ else
+ next_timeout = jiffies + HZ;
} else
next_timeout = last_recv + recv_timeout;
--
1.7.7.4
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
