netdev - [PATCH V1 net 6/8] net: ena: improve latency by disabling adaptive interrupt moderation by default

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Date:   Wed, 1 May 2019 16:47:08 +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>
Subject: [PATCH V1 net 6/8] net: ena: improve latency by disabling adaptive interrupt moderation by default

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

Adaptive interrupt moderation was erroneously enabled by default
in the driver.

In case the device supports adaptive interrupt moderation it will
be automatically used, which may potentially increase latency.

The adaptive moderation can be enabled from ethtool command in
case the feature is supported by the device.

Fixes: 1738cd3ed342 ("net: ena: Add a driver for Amazon Elastic Network Adapters (ENA)")

Signed-off-by: Guy Tzalik <gtzalik@...zon.com>
Signed-off-by: Sameeh Jubran <sameehj@...zon.com>
---
 drivers/net/ethernet/amazon/ena/ena_com.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_com.c b/drivers/net/ethernet/amazon/ena/ena_com.c
index 4fe437fe771b..677d31abf214 100644
--- a/drivers/net/ethernet/amazon/ena/ena_com.c
+++ b/drivers/net/ethernet/amazon/ena/ena_com.c
@@ -2802,7 +2802,11 @@ int ena_com_init_interrupt_moderation(struct ena_com_dev *ena_dev)
 	/* if moderation is supported by device we set adaptive moderation */
 	delay_resolution = get_resp.u.intr_moderation.intr_delay_resolution;
 	ena_com_update_intr_delay_resolution(ena_dev, delay_resolution);
-	ena_com_enable_adaptive_moderation(ena_dev);
+
+	/* Disable adaptive moderation by default - can be enabled from
+	 * ethtool
+	 */
+	ena_com_disable_adaptive_moderation(ena_dev);
 
 	return 0;
 err:
-- 
2.17.1