tun supports zero copy transmit since 0690899b4d4501b3505be069b9a687e68ccbe15b, however you can only enable this mode if you know your workload does not trigger heavy guest to host/host to guest traffic - otherwise you get a (minor) performance regression. This patchset addresses this problem by notifying the owner device when callback is invoked because of a data copy. This makes it possible to detect whether zero copy is appropriate dynamically: we start in zero copy mode, when we detect data copied we disable zero copy for a while. With this patch applied, I get the same performance for guest to host and guest to guest both with and without zero copy tx. Michael S. Tsirkin (8): skb: report completion status for zero copy skbs skb: api to report errors for zero copy skbs tun: report orphan frags errors to zero copy callback vhost-net: cleanup macros for DMA status tracking vhost: track zero copy failures using DMA length vhost: move -net specific code out vhost-net: select tx zero copy dynamically vhost-net: reduce vq polling on tx zerocopy drivers/net/tun.c | 1 + drivers/vhost/net.c | 109 +++++++++++++++++++++++++++++++++++++++++++--- drivers/vhost/tcm_vhost.c | 1 + drivers/vhost/vhost.c | 52 +++------------------- drivers/vhost/vhost.h | 11 ++--- include/linux/skbuff.h | 5 ++- net/core/skbuff.c | 23 +++++++++- 7 files changed, 141 insertions(+), 61 deletions(-) -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
