On Wednesday 21 May 2008 08:37:54 Olaf Kirch wrote:
> Anyway, when I take the brief detour through SQD state, resetting the RNR
> retry count seems to work.
For those willing to test this, I committed the following patch to
branch future-20080519 on my git tree.
Olaf
--
Olaf Kirch | --- o --- Nous sommes du soleil we love when we play
[EMAIL PROTECTED] | / | \ sol.dhoop.naytheet.ah kin.ir.samse.qurax
-----
commit 735bdc95be33db4f21051c0d50090bc128719d98
Author: Olaf Kirch <[EMAIL PROTECTED]>
Date: Tue May 20 22:41:04 2008 -0700
RDS: disable RNR retries when flow control is on
When flow control is enabled on a connection, we don't need RNR
retries. Turning them off allows us to detect potential bugs in
the credit accounting more quickly.
Signed-off-by: Olaf Kirch <[EMAIL PROTECTED]>
diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c
index 20c888d..a49e394 100644
--- a/net/rds/ib_cm.c
+++ b/net/rds/ib_cm.c
@@ -99,21 +99,40 @@ static void rds_ib_connect_complete(struct rds_connection
*conn, struct rdma_cm_
rds_ib_recv_refill(conn, GFP_KERNEL, GFP_HIGHUSER, 1);
- /* Tune the RNR timeout. We use a rather low timeout, but
- * not the absolute minimum - this should be tunable.
+ /* Tune RNR behavior. Without flow control, we use a rather
+ * low timeout, but not the absolute minimum - this should
+ * be tunable.
*
* We already set the RNR retry count to 7 (which is the
- * smallest infinite number :-) above
+ * smallest infinite number :-) above.
+ * If flow control is off, we want to change this back to 0
+ * so that we learn quickly when our credit accounting is
+ * buggy.
*/
- qp_attr.qp_state = IB_QPS_RTS;
- qp_attr.min_rnr_timer = IB_RNR_TIMER_000_32;
- ret = ib_modify_qp(ic->i_cm_id->qp, &qp_attr,
- IB_QP_STATE | IB_QP_MIN_RNR_TIMER);
- if (ret) {
- printk(KERN_NOTICE "ib_modify_qp(IB_QP_MIN_RNR_TIMER, %u):
err=%d\n",
- qp_attr.min_rnr_timer, -ret);
+ if (ic->i_flowctl) {
+ /* It seems we have to take a brief detour through SQD state
+ * in order to change the RNR retry count. */
+ qp_attr.qp_state = IB_QPS_SQD;
+ ret = ib_modify_qp(ic->i_cm_id->qp, &qp_attr, IB_QP_STATE);
+ if (ret)
+ printk(KERN_NOTICE "ib_modify_qp(IB_QP_STATE, SQD):
err=%d\n", -ret);
+
+ qp_attr.rnr_retry = 0;
+ ret = ib_modify_qp(ic->i_cm_id->qp, &qp_attr, IB_QP_RNR_RETRY);
+ if (ret)
+ printk(KERN_NOTICE "ib_modify_qp(IB_QP_RNR_RETRY, 0):
err=%d\n", -ret);
+ } else {
+ qp_attr.min_rnr_timer = IB_RNR_TIMER_000_32;
+ ret = ib_modify_qp(ic->i_cm_id->qp, &qp_attr,
IB_QP_MIN_RNR_TIMER);
+ if (ret)
+ printk(KERN_NOTICE "ib_modify_qp(IB_QP_MIN_RNR_TIMER):
err=%d\n", -ret);
}
+ qp_attr.qp_state = IB_QPS_RTS;
+ ret = ib_modify_qp(ic->i_cm_id->qp, &qp_attr, IB_QP_STATE);
+ if (ret)
+ printk(KERN_NOTICE "ib_modify_qp(IB_QP_STATE, RTS): err=%d\n",
-ret);
+
/* update ib_device with this local ipaddr */
rds_ibdev = ib_get_client_data(ic->i_cm_id->device, &rds_ib_client);
ib_update_ipaddr_for_device(rds_ibdev, conn->c_laddr);
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