[hermon] Limit link poll frequency in DOWN state

Some older versions of the hardware (and/or firmware) do not report an
event when an Infiniband link reaches the INIT state.  The driver
works around this missing event by calling ib_smc_update() on each
event queue poll while the link is in the DOWN state.

Commit 6cb12ee ("[hermon] Increase polling rate for command
completions") addressed this by speeding up the time taken to issue
each command invoked by ib_smc_update().  Experimentation shows that
the impact is still significant: for example, in a situation where an
unplugged port is opened, the throughput on the other port can be
reduced by over 99%.

Fix by throttling the rate at which link polling is attempted.

Debugged-by: Christian Iversen <ci@iversenit.dk>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/drivers/infiniband/hermon.c b/src/drivers/infiniband/hermon.c
index 2a9649de2d545e8dba0fff5bd27d816f7be780fb..50ba4f4e8049bdd3b8255801328fc7708891d219 100644 (file)
--- a/src/drivers/infiniband/hermon.c
+++ b/src/drivers/infiniband/hermon.c
@@ -2130,6 +2130,8 @@ static void hermon_poll_eq ( struct ib_device *ibdev ) {
        struct hermon_event_queue *hermon_eq = &hermon->eq;
        union hermonprm_event_entry *eqe;
        union hermonprm_doorbell_register db_reg;
+       unsigned long now;
+       unsigned long elapsed;
        unsigned int eqe_idx_mask;
        unsigned int event_type;
 
@@ -2138,7 +2140,12 @@ static void hermon_poll_eq ( struct ib_device *ibdev ) {
         */
        if ( ib_is_open ( ibdev ) &&
             ( ibdev->port_state == IB_PORT_STATE_DOWN ) ) {
-               ib_smc_update ( ibdev, hermon_mad );
+               now = currticks();
+               elapsed = ( now - hermon->last_poll );
+               if ( elapsed >= HERMON_LINK_POLL_INTERVAL ) {
+                       hermon->last_poll = now;
+                       ib_smc_update ( ibdev, hermon_mad );
+               }
        }
 
        /* Poll event queue */

diff --git a/src/drivers/infiniband/hermon.h b/src/drivers/infiniband/hermon.h
index 61f3b04186d40c00f89bc1e337fb4c25c65a6b05..6d7471dfdffb7e1329a428c4f744e1225c48733f 100644 (file)
--- a/src/drivers/infiniband/hermon.h
+++ b/src/drivers/infiniband/hermon.h
@@ -894,6 +894,8 @@ struct hermon {
 
        /** Event queue */
        struct hermon_event_queue eq;
+       /** Last unsolicited link state poll */
+       unsigned long last_poll;
        /** Unrestricted LKey
         *
         * Used to get unrestricted memory access.
@@ -930,6 +932,13 @@ struct hermon {
 /** Memory key prefix */
 #define HERMON_MKEY_PREFIX             0x77000000UL
 
+/** Link poll interval
+ *
+ * Used when we need to poll for link state (rather than relying upon
+ * receiving an event).
+ */
+#define HERMON_LINK_POLL_INTERVAL      ( TICKS_PER_SEC / 2 )
+
 /*
  * HCA commands
  *