Linux Virtualization - Jul 2019 - [PATCH AUTOSEL 4.19 079/158] vhost_net: disable zerocopy by default

From: Jason Wang <jasowang at redhat.com>

[ Upstream commit 098eadce3c622c07b328d0a43dda379b38cf7c5e ]

Vhost_net was known to suffer from HOL[1] issues which is not easy to
fix. Several downstream disable the feature by default. What's more,
the datapath was split and datacopy path got the support of batching
and XDP support recently which makes it faster than zerocopy part for
small packets transmission.

It looks to me that disable zerocopy by default is more
appropriate. It cold be enabled by default again in the future if we
fix the above issues.

[1] https://patchwork.kernel.org/patch/3787671/

Signed-off-by: Jason Wang <jasowang at redhat.com>
Acked-by: Michael S. Tsirkin <mst at redhat.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 drivers/vhost/net.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 39155d7cc894..ae704658b528 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -36,7 +36,7 @@
 
 #include "vhost.h"
 
-static int experimental_zcopytx = 1;
+static int experimental_zcopytx = 0;
 module_param(experimental_zcopytx, int, 0444);
 MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
 		                       " 1 -Enable; 0 - Disable");
-- 
2.20.1