IB/hfi1: Prioritize the sending of ACK packets

ACK packets are generally associated with request completion and resource
release and therefore should be sent first. This patch optimizes the
send engine by using the following policies:
(1) QPs with RVT_S_ACK_PENDING bit set in qp->s_flags or qpriv->s_flags
should have their priority incremented;
(2) QPs with ACK or TID-ACK packet queued should have their priority
incremented;
(3) When a QP is queued to the wait list due to resource constraints, it
will be queued to the head if it has ACK packet to send;
(4) When selecting qps to run from the wait list, the one with the highest
priority and starve_cnt will be selected; each priority will be equivalent
to a fixed number of starve_cnt (16).

Reviewed-by: Mitko Haralanov <mitko.haralanov@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

1 files changed, 33 insertions, 1 deletions

diff --git a/drivers/infiniband/hw/hfi1/iowait.c b/drivers/infiniband/hw/hfi1/iowait.c
index 582f1ba136ff..adb4a1ba921b 100644
--- a/drivers/infiniband/hw/hfi1/iowait.c
+++ b/drivers/infiniband/hw/hfi1/iowait.c
@@ -6,6 +6,9 @@
 #include "iowait.h"
 #include "trace_iowait.h"
 
+/* 1 priority == 16 starve_cnt */
+#define IOWAIT_PRIORITY_STARVE_SHIFT 4
+
 void iowait_set_flag(struct iowait *wait, u32 flag)
 {
 	trace_hfi1_iowait_set(wait, flag);
@@ -44,7 +47,8 @@ void iowait_init(struct iowait *wait, u32 tx_limit,
 			      uint seq,
 			      bool pkts_sent),
 		 void (*wakeup)(struct iowait *wait, int reason),
-		 void (*sdma_drained)(struct iowait *wait))
+		 void (*sdma_drained)(struct iowait *wait),
+		 void (*init_priority)(struct iowait *wait))
 {
 	int i;
 
@@ -58,6 +62,7 @@ void iowait_init(struct iowait *wait, u32 tx_limit,
 	wait->sleep = sleep;
 	wait->wakeup = wakeup;
 	wait->sdma_drained = sdma_drained;
+	wait->init_priority = init_priority;
 	wait->flags = 0;
 	for (i = 0; i < IOWAIT_SES; i++) {
 		wait->wait[i].iow = wait;
@@ -92,3 +97,30 @@ int iowait_set_work_flag(struct iowait_work *w)
 	iowait_set_flag(w->iow, IOWAIT_PENDING_TID);
 	return IOWAIT_TID_SE;
 }
+
+/**
+ * iowait_priority_update_top - update the top priority entry
+ * @w: the iowait struct
+ * @top: a pointer to the top priority entry
+ * @idx: the index of the current iowait in an array
+ * @top_idx: the array index for the iowait entry that has the top priority
+ *
+ * This function is called to compare the priority of a given
+ * iowait with the given top priority entry. The top index will
+ * be returned.
+ */
+uint iowait_priority_update_top(struct iowait *w,
+				struct iowait *top,
+				uint idx, uint top_idx)
+{
+	u8 cnt, tcnt;
+
+	/* Convert priority into starve_cnt and compare the total.*/
+	cnt = (w->priority << IOWAIT_PRIORITY_STARVE_SHIFT) + w->starved_cnt;
+	tcnt = (top->priority << IOWAIT_PRIORITY_STARVE_SHIFT) +
+		top->starved_cnt;
+	if (cnt > tcnt)
+		return idx;
+	else
+		return top_idx;
+}