From b9200da0c527ab4ca6c72b91bb2c775fd517b3c7 Mon Sep 17 00:00:00 2001 From: Thomas Lamprecht Date: Wed, 21 Aug 2019 09:50:07 +0200 Subject: [PATCH] backport vhost_net: disable zerocopy by default It seems to make general problems[0], and upstream changed the default back to 0 again[1] (was enabled long ago, ca. 2012). [0]: https://pve.proxmox.com/pipermail/pve-devel/2019-August/038571.html [1]: https://git.kernel.org/torvalds/c/098eadce3c622c07b328d0a43dda379b38cf7c5e Signed-off-by: Thomas Lamprecht --- ...host_net-disable-zerocopy-by-default.patch | 40 +++++++++++++++++++ 1 file changed, 40 insertions(+) create mode 100644 patches/kernel/0007-vhost_net-disable-zerocopy-by-default.patch diff --git a/patches/kernel/0007-vhost_net-disable-zerocopy-by-default.patch b/patches/kernel/0007-vhost_net-disable-zerocopy-by-default.patch new file mode 100644 index 0000000..e384d6a --- /dev/null +++ b/patches/kernel/0007-vhost_net-disable-zerocopy-by-default.patch @@ -0,0 +1,40 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: Jason Wang +Date: Mon, 17 Jun 2019 05:20:54 -0400 +Subject: [PATCH] vhost_net: disable zerocopy by default + +[ 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 +Acked-by: Michael S. Tsirkin +Signed-off-by: David S. Miller +Signed-off-by: Sasha Levin +--- + 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 2d9df786a9d3..21e0805e5e60 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");