linux-kernel - [PATCH] vhost-net: add time limitation for tx polling

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Message-ID: <88D661ADF6AFBF42B2AB88D8E7682B0901FC4059@EXMBX-SZMAIL011.tencent.com>
Date:   Tue, 27 Mar 2018 09:12:27 +0000
From:   haibinzhang(张海斌) <haibinzhang@...cent.com>
To:     "mst@...hat.com" <mst@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] vhost-net: add time limitation for tx polling

handle_tx() will delay rx for a long time when busy tx polling udp packets
with short length(ie: 1byte udp payload), because setting VHOST_NET_WEIGHT
takes into account only sent-bytes but no time. It's not fair for handle_rx(),
so needs to limit max time of tx polling.

Signed-off-by: Haibin Zhang <haibinzhang@...cent.com>
---
 drivers/vhost/net.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 8139bc70ad7d..dc9218a3a75b 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -473,6 +473,7 @@ static void handle_tx(struct vhost_net *net)
 	struct socket *sock;
 	struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
 	bool zcopy, zcopy_used;
+	unsigned long start = jiffies;
 
 	mutex_lock(&vq->mutex);
 	sock = vq->private_data;
@@ -580,7 +581,7 @@ static void handle_tx(struct vhost_net *net)
 		else
 			vhost_zerocopy_signal_used(net, vq);
 		vhost_net_tx_packet(net);
-		if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
+		if (unlikely(total_len >= VHOST_NET_WEIGHT) || unlikely(jiffies - start >= 1)) {
 			vhost_poll_queue(&vq->poll);
 			break;
 		}
-- 
2.12.3