linux-kernel - [PATCH 2.6 8/8] RDMA/nes: Fix interrupt moderation low threshold

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Date:	Thu, 21 Feb 2008 08:34:58 -0600
From:	gstreiff@...effect.com
To:	rdreier@...co.com
Cc:	general@...ts.openfabrics.org, jlacombe@...effect.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2.6 8/8] RDMA/nes: Fix interrupt moderation low threshold

From: John Lacombe <jlacombe@...effect.com>

Interrupt moderation low threshold value was incorrectly
triggering, indicating that the threshold should be lowered.

The impact was the timer was likely to become 40usecs and get
stuck there.  The biggest side effect was too many interrupts
and nonoptimal performance.

Signed-off-by: John Lacombe <jlacombe@...effect.com>
Signed-off-by: Glenn Streiff <gstreiff@...effect.com>

---
 drivers/infiniband/hw/nes/nes_hw.c |   12 ++++--------
 drivers/infiniband/hw/nes/nes_hw.h |    2 +-
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/infiniband/hw/nes/nes_hw.c b/drivers/infiniband/hw/nes/nes_hw.c
index 7c4c0fb..6b677b5 100644
--- a/drivers/infiniband/hw/nes/nes_hw.c
+++ b/drivers/infiniband/hw/nes/nes_hw.c
@@ -156,15 +156,13 @@ static void nes_nic_tune_timer(struct nes_device *nesdev)
 
 	spin_lock_irqsave(&nesadapter->periodic_timer_lock, flags);
 
-	if (shared_timer->cq_count_old < cq_count) {
-		if (cq_count > shared_timer->threshold_low)
-			shared_timer->cq_direction_downward=0;
-	}
-	if (shared_timer->cq_count_old >= cq_count)
+	if (shared_timer->cq_count_old <= cq_count)
+		shared_timer->cq_direction_downward = 0;
+	else
 		shared_timer->cq_direction_downward++;
 	shared_timer->cq_count_old = cq_count;
 	if (shared_timer->cq_direction_downward > NES_NIC_CQ_DOWNWARD_TREND) {
-		if (cq_count <= shared_timer->threshold_low) {
+		if (cq_count <= shared_timer->threshold_low && (shared_timer->threshold_low > 4)) {
 			shared_timer->threshold_low = shared_timer->threshold_low/2;
 			shared_timer->cq_direction_downward=0;
 			nesdev->currcq_count = 0;
@@ -1728,7 +1726,6 @@ int nes_napi_isr(struct nes_device *nesdev)
 			nesdev->int_req &= ~NES_INT_TIMER;
 			nes_write32(nesdev->regs+NES_INTF_INT_MASK, ~(nesdev->intf_int_req));
 			nes_write32(nesdev->regs+NES_INT_MASK, ~nesdev->int_req);
-			nesadapter->tune_timer.timer_in_use_old = 0;
 		}
 		nesdev->deepcq_count = 0;
 		return 1;
@@ -1867,7 +1864,6 @@ void nes_dpc(unsigned long param)
 					nesdev->int_req &= ~NES_INT_TIMER;
 					nes_write32(nesdev->regs + NES_INTF_INT_MASK, ~(nesdev->intf_int_req));
 					nes_write32(nesdev->regs+NES_INT_MASK, ~nesdev->int_req);
-					nesdev->nesadapter->tune_timer.timer_in_use_old = 0;
 				} else {
 					nes_write32(nesdev->regs+NES_INT_MASK, 0x0000ffff|(~nesdev->int_req));
 				}
diff --git a/drivers/infiniband/hw/nes/nes_hw.h b/drivers/infiniband/hw/nes/nes_hw.h
index 1e10df5..b7e2844 100644
--- a/drivers/infiniband/hw/nes/nes_hw.h
+++ b/drivers/infiniband/hw/nes/nes_hw.h
@@ -962,7 +962,7 @@ struct nes_arp_entry {
 #define DEFAULT_JUMBO_NES_QL_LOW    12
 #define DEFAULT_JUMBO_NES_QL_TARGET 40
 #define DEFAULT_JUMBO_NES_QL_HIGH   128
-#define NES_NIC_CQ_DOWNWARD_TREND   8
+#define NES_NIC_CQ_DOWNWARD_TREND   16
 
 struct nes_hw_tune_timer {
     //u16 cq_count;
--
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