netdev - [PATCH V2 net 09/11] net: ena: optimise calculations for CQ doorbell

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Message-ID: <20190603144329.16366-10-sameehj@amazon.com>
Date:   Mon, 3 Jun 2019 17:43:27 +0300
From:   <sameehj@...zon.com>
To:     <davem@...emloft.net>, <netdev@...r.kernel.org>
CC:     Sameeh Jubran <sameehj@...zon.com>, <dwmw@...zon.com>,
        <zorik@...zon.com>, <matua@...zon.com>, <saeedb@...zon.com>,
        <msw@...zon.com>, <aliguori@...zon.com>, <nafea@...zon.com>,
        <gtzalik@...zon.com>, <netanel@...zon.com>, <alisaidi@...zon.com>,
        <benh@...zon.com>, <akiyano@...zon.com>,
        Igor Chauskin <igorch@...zon.com>
Subject: [PATCH V2 net 09/11] net: ena: optimise calculations for CQ doorbell

From: Sameeh Jubran <sameehj@...zon.com>

This patch initially checks if CQ doorbell
is needed before proceeding with the calculations.

Signed-off-by: Igor Chauskin <igorch@...zon.com>
Signed-off-by: Sameeh Jubran <sameehj@...zon.com>
---
 drivers/net/ethernet/amazon/ena/ena_eth_com.h | 20 ++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_eth_com.h b/drivers/net/ethernet/amazon/ena/ena_eth_com.h
index 0a3d9180e..77986c0ea 100644
--- a/drivers/net/ethernet/amazon/ena/ena_eth_com.h
+++ b/drivers/net/ethernet/amazon/ena/ena_eth_com.h
@@ -195,15 +195,17 @@ static inline int ena_com_update_dev_comp_head(struct ena_com_io_cq *io_cq)
 	u16 unreported_comp, head;
 	bool need_update;
 
-	head = io_cq->head;
-	unreported_comp = head - io_cq->last_head_update;
-	need_update = unreported_comp > (io_cq->q_depth / ENA_COMP_HEAD_THRESH);
-
-	if (io_cq->cq_head_db_reg && need_update) {
-		pr_debug("Write completion queue doorbell for queue %d: head: %d\n",
-			 io_cq->qid, head);
-		writel(head, io_cq->cq_head_db_reg);
-		io_cq->last_head_update = head;
+	if (unlikely(io_cq->cq_head_db_reg)) {
+		head = io_cq->head;
+		unreported_comp = head - io_cq->last_head_update;
+		need_update = unreported_comp > (io_cq->q_depth / ENA_COMP_HEAD_THRESH);
+
+		if (unlikely(need_update)) {
+			pr_debug("Write completion queue doorbell for queue %d: head: %d\n",
+				 io_cq->qid, head);
+			writel(head, io_cq->cq_head_db_reg);
+			io_cq->last_head_update = head;
+		}
 	}
 
 	return 0;
-- 
2.17.1