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.
Changes from v2:
change callback parameter from int to bool
accordingly, drop err parameter from skb_tx_error
Changes from v1:
Comment fixups in patches 2 and 8 suggested by Vlad Yasevich,
no changes to other patches
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 | 111 +++++++++++++++++++++++++++++++++++++++++++---
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 | 24 +++++++++-
7 files changed, 144 insertions(+), 61 deletions(-)
--
MST
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