Re: [PATCH v2 net-next 0/4] vhost_net: Avoid vq kicks during busyloop

Michael S. Tsirkin
2018-07-04T05:35:30Z

On Tue, Jul 03, 2018 at 04:31:30PM +0900, Toshiaki Makita wrote:
> Under heavy load vhost tx busypoll tend not to suppress vq kicks, which
> causes poor guest tx performance. The detailed scenario is described in
> commitlog of patch 2.
> Rx seems not to have that serious problem, but for consistency I made a
> similar change on rx to avoid rx wakeups (patch 3).
> Additionary patch 4 is to avoid rx kicks under heavy load during
> busypoll.
>
> Tx performance is greatly improved by this change. I don't see notable
> performance change on rx with this series though.
>
> Performance numbers (tx):
>
> - Bulk transfer from guest to external physical server.
> [Guest]->vhost_net->tap--(XDP_REDIRECT)-->i40e --(wire)--> [Server]
> - Set 10us busypoll.
> - Guest disables checksum and TSO because of host XDP.
> - Measured single flow Mbps by netperf, and kicks by perf kvm stat
> (EPT_MISCONFIG event).
>
> Before After
> Mbps kicks/s Mbps kicks/s
> UDP_STREAM 1472byte 247758 27
> Send 3645.37 6958.10
> Recv 3588.56 6958.10
> 1byte 9865 37
> Send 4.34 5.43
> Recv 4.17 5.26
> TCP_STREAM 8801.03 45794 9592.77 2884

Thanks!
Series:

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> v2:
> - Split patches into 3 parts (renaming variables, tx-kick fix, rx-wakeup
> fix).
> - Avoid rx-kicks too (patch 4).
> - Don't memorize endtime as it is not needed for now.
>
> Toshiaki Makita (4):
> vhost_net: Rename local variables in vhost_net_rx_peek_head_len
> vhost_net: Avoid tx vring kicks during busyloop
> vhost_net: Avoid rx queue wake-ups during busypoll
> vhost_net: Avoid rx vring kicks during busyloop
>
> drivers/vhost/net.c | 95 +++++++++++++++++++++++++++++++++--------------------
> 1 file changed, 60 insertions(+), 35 deletions(-)
>
> --
> 1.8.3.1
>