ixgbe: Restore AIM support

AIM (adaptive interrupt moderation) was part of BSD11 driver. Upon IFLIB
migration, AIM feature got lost. Re-introducing AIM back into IFLIB
based IXGBE driver.

One caveat is that in BSD11 driver, a queue comprises both Rx and Tx
ring. Starting from BSD12, Rx and Tx have their own queues and rings.
Also, IRQ is now only configured for Rx side. So, when AIM is
re-enabled, we should now consider only Rx stats for configuring EITR
register in contrast to BSD11 where Rx and Tx stats were considered to
manipulate EITR register.

Reviewed by:	gallatin, markj
Sponsored by:	NetApp, Inc.
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D27344

1 files changed, 73 insertions, 0 deletions

diff --git a/sys/dev/ixgbe/if_ix.c b/sys/dev/ixgbe/if_ix.c
index 489e891cf509..fbe4f1df38ca 100644
--- a/sys/dev/ixgbe/if_ix.c
+++ b/sys/dev/ixgbe/if_ix.c
@@ -347,6 +347,16 @@ static int ixgbe_enable_rss = 1;
 SYSCTL_INT(_hw_ix, OID_AUTO, enable_rss, CTLFLAG_RDTUN, &ixgbe_enable_rss, 0,
     "Enable Receive-Side Scaling (RSS)");
 
+/*
+ * AIM: Adaptive Interrupt Moderation
+ * which means that the interrupt rate
+ * is varied over time based on the
+ * traffic for that interrupt vector
+ */
+static int ixgbe_enable_aim = FALSE;
+SYSCTL_INT(_hw_ix, OID_AUTO, enable_aim, CTLFLAG_RWTUN, &ixgbe_enable_aim, 0,
+    "Enable adaptive interrupt moderation");
+
 #if 0
 /* Keep running tab on them for sanity check */
 static int ixgbe_total_ports;
@@ -2100,6 +2110,60 @@ fail:
 	return (error);
 } /* ixgbe_if_msix_intr_assign */
 
+static inline void
+ixgbe_perform_aim(struct adapter *adapter, struct ix_rx_queue *que)
+{
+	uint32_t newitr = 0;
+	struct rx_ring *rxr = &que->rxr;
+
+	/*
+	 * Do Adaptive Interrupt Moderation:
+	 *  - Write out last calculated setting
+	 *  - Calculate based on average size over
+	 *    the last interval.
+	 */
+	if (que->eitr_setting) {
+		IXGBE_WRITE_REG(&adapter->hw, IXGBE_EITR(que->msix),
+		    que->eitr_setting);
+	}
+
+	que->eitr_setting = 0;
+	/* Idle, do nothing */
+	if (rxr->bytes == 0) {
+		return;
+	}
+
+	if ((rxr->bytes) && (rxr->packets)) {
+		newitr = (rxr->bytes / rxr->packets);
+	}
+
+	newitr += 24; /* account for hardware frame, crc */
+	/* set an upper boundary */
+	newitr = min(newitr, 3000);
+
+	/* Be nice to the mid range */
+	if ((newitr > 300) && (newitr < 1200)) {
+		newitr = (newitr / 3);
+	} else {
+		newitr = (newitr / 2);
+	}
+
+	if (adapter->hw.mac.type == ixgbe_mac_82598EB) {
+		newitr |= newitr << 16;
+	} else {
+		newitr |= IXGBE_EITR_CNT_WDIS;
+	}
+
+	/* save for next interrupt */
+	que->eitr_setting = newitr;
+
+	/* Reset state */
+	rxr->bytes = 0;
+	rxr->packets = 0;
+
+	return;
+}
+
 /*********************************************************************
  * ixgbe_msix_que - MSI-X Queue Interrupt Service routine
  **********************************************************************/
@@ -2117,6 +2181,11 @@ ixgbe_msix_que(void *arg)
 	ixgbe_disable_queue(adapter, que->msix);
 	++que->irqs;
 
+	/* Check for AIM */
+	if (adapter->enable_aim) {
+		ixgbe_perform_aim(adapter, que);
+	}
+
 	return (FILTER_SCHEDULE_THREAD);
 } /* ixgbe_msix_que */
 
@@ -2575,6 +2644,10 @@ ixgbe_add_device_sysctls(if_ctx_t ctx)
 	    adapter, 0, ixgbe_sysctl_advertise, "I",
 	    IXGBE_SYSCTL_DESC_ADV_SPEED);
 
+	adapter->enable_aim = ixgbe_enable_aim;
+	SYSCTL_ADD_INT(ctx_list, child, OID_AUTO, "enable_aim", CTLFLAG_RW,
+	    &adapter->enable_aim, 0, "Interrupt Moderation");
+
 #ifdef IXGBE_DEBUG
 	/* testing sysctls (for all devices) */
 	SYSCTL_ADD_PROC(ctx_list, child, OID_AUTO, "power_state",