netdev - [PATCH] virtio_net: send notification coalescing command only if value changed

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Message-Id: <20221221120618.652074-1-alvaro.karsz@solid-run.com>
Date:   Wed, 21 Dec 2022 14:06:18 +0200
From:   Alvaro Karsz <alvaro.karsz@...id-run.com>
To:     virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Cc:     Alvaro Karsz <alvaro.karsz@...id-run.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH] virtio_net: send notification coalescing command only if value changed

Don't send a VIRTIO_NET_CTRL_NOTF_COAL_TX_SET or
VIRTIO_NET_CTRL_NOTF_COAL_RX_SET command if the coalescing parameters
haven't changed.

Signed-off-by: Alvaro Karsz <alvaro.karsz@...id-run.com>
---
 drivers/net/virtio_net.c | 48 ++++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 21 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 7723b2a49d8..1d7118de62a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2760,31 +2760,37 @@ static int virtnet_send_notf_coal_cmds(struct virtnet_info *vi,
 	struct virtio_net_ctrl_coal_tx coal_tx;
 	struct virtio_net_ctrl_coal_rx coal_rx;
 
-	coal_tx.tx_usecs = cpu_to_le32(ec->tx_coalesce_usecs);
-	coal_tx.tx_max_packets = cpu_to_le32(ec->tx_max_coalesced_frames);
-	sg_init_one(&sgs_tx, &coal_tx, sizeof(coal_tx));
-
-	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
-				  VIRTIO_NET_CTRL_NOTF_COAL_TX_SET,
-				  &sgs_tx))
-		return -EINVAL;
+	if (ec->tx_coalesce_usecs != vi->tx_usecs ||
+	    ec->tx_max_coalesced_frames != vi->tx_max_packets) {
+		coal_tx.tx_usecs = cpu_to_le32(ec->tx_coalesce_usecs);
+		coal_tx.tx_max_packets = cpu_to_le32(ec->tx_max_coalesced_frames);
+		sg_init_one(&sgs_tx, &coal_tx, sizeof(coal_tx));
+
+		if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
+					  VIRTIO_NET_CTRL_NOTF_COAL_TX_SET,
+					  &sgs_tx))
+			return -EINVAL;
 
-	/* Save parameters */
-	vi->tx_usecs = ec->tx_coalesce_usecs;
-	vi->tx_max_packets = ec->tx_max_coalesced_frames;
+		/* Save parameters */
+		vi->tx_usecs = ec->tx_coalesce_usecs;
+		vi->tx_max_packets = ec->tx_max_coalesced_frames;
+	}
 
-	coal_rx.rx_usecs = cpu_to_le32(ec->rx_coalesce_usecs);
-	coal_rx.rx_max_packets = cpu_to_le32(ec->rx_max_coalesced_frames);
-	sg_init_one(&sgs_rx, &coal_rx, sizeof(coal_rx));
+	if (ec->rx_coalesce_usecs != vi->rx_usecs ||
+	    ec->rx_max_coalesced_frames != vi->rx_max_packets) {
+		coal_rx.rx_usecs = cpu_to_le32(ec->rx_coalesce_usecs);
+		coal_rx.rx_max_packets = cpu_to_le32(ec->rx_max_coalesced_frames);
+		sg_init_one(&sgs_rx, &coal_rx, sizeof(coal_rx));
 
-	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
-				  VIRTIO_NET_CTRL_NOTF_COAL_RX_SET,
-				  &sgs_rx))
-		return -EINVAL;
+		if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_NOTF_COAL,
+					  VIRTIO_NET_CTRL_NOTF_COAL_RX_SET,
+					  &sgs_rx))
+			return -EINVAL;
 
-	/* Save parameters */
-	vi->rx_usecs = ec->rx_coalesce_usecs;
-	vi->rx_max_packets = ec->rx_max_coalesced_frames;
+		/* Save parameters */
+		vi->rx_usecs = ec->rx_coalesce_usecs;
+		vi->rx_max_packets = ec->rx_max_coalesced_frames;
+	}
 
 	return 0;
 }
-- 
2.32.0