Re: [PATCH 0/6] vhost: add Tx zero copy support

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Mon, Aug 29, 2016 at 08:32:55AM +0000, Xu, Qian Q wrote:
> I just ran a PVP test, nic receive packets then forwards to vhost PMD, and virtio user interface. I didn't see any performance gains in this scenario. All packet size from 64B to 1518B 
> performance haven't got benefit from this patchset, and in fact, the performance dropped a lot before 1280B, and similar at 1518B. 

40G nic?

> The TX/RX desc setting is " txd=64, rxd=128"

Try it with "txd=128", you should be able to set that value since the
vhost Tx indirect patch is merged.

	--yliu

> for TX-zero-copy enabled case. For TX-zero-copy disabled case, I just ran default testpmd(txd=512, rxd=128) without the patch. 
> Could you help check if NIC2VM case? 
> 
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Yuanhan Liu
> Sent: Tuesday, August 23, 2016 4:11 PM
> To: dev@dpdk.org
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>; Yuanhan Liu <yuanhan.liu@linux.intel.com>
> Subject: [dpdk-dev] [PATCH 0/6] vhost: add Tx zero copy support
> 
> This patch set enables vhost Tx zero copy. The majority work goes to patch 4: vhost: add Tx zero copy.
> 
> The basic idea of Tx zero copy is, instead of copying data from the desc buf, here we let the mbuf reference the desc buf addr directly.
> 
> The major issue behind that is how and when to update the used ring.
> You could check the commit log of patch 4 for more details.
> 
> Patch 5 introduces a new flag, RTE_VHOST_USER_TX_ZERO_COPY, to enable Tx zero copy, which is disabled by default.
> 
> Few more TODOs are left, including handling a desc buf that is across two physical pages, updating release note, etc. Those will be fixed in later version. For now, here is a simple one that hopefully it shows the idea clearly.
> 
> I did some quick tests, the performance gain is quite impressive.
> 
> For a simple dequeue workload (running rxonly in vhost-pmd and runnin txonly in guest testpmd), it yields 40+% performance boost for packet size 1400B.
> 
> For VM2VM iperf test case, it's even better: about 70% boost.
> 
> ---
> Yuanhan Liu (6):
>   vhost: simplify memory regions handling
>   vhost: get guest/host physical address mappings
>   vhost: introduce last avail idx for Tx
>   vhost: add Tx zero copy
>   vhost: add a flag to enable Tx zero copy
>   examples/vhost: add an option to enable Tx zero copy
> 
>  doc/guides/prog_guide/vhost_lib.rst |   7 +-
>  examples/vhost/main.c               |  19 ++-
>  lib/librte_vhost/rte_virtio_net.h   |   1 +
>  lib/librte_vhost/socket.c           |   5 +
>  lib/librte_vhost/vhost.c            |  12 ++
>  lib/librte_vhost/vhost.h            | 103 +++++++++----
>  lib/librte_vhost/vhost_user.c       | 297 +++++++++++++++++++++++-------------
>  lib/librte_vhost/virtio_net.c       | 188 +++++++++++++++++++----
>  8 files changed, 472 insertions(+), 160 deletions(-)
> 
> --
> 1.9.0