[dpdk-dev] [PATCH] vhost: adaptively batch small guest memory copies

[Tiwei Bie]

Hi Maxime,

On Thu, Sep 07, 2017 at 07:47:57PM +0200, Maxime Coquelin wrote:
> Hi Tiwei,
> 
> On 08/24/2017 04:19 AM, Tiwei Bie wrote:
> > This patch adaptively batches the small guest memory copies.
> > By batching the small copies, the efficiency of executing the
> > memory LOAD instructions can be improved greatly, because the
> > memory LOAD latency can be effectively hidden by the pipeline.
> > We saw great performance boosts for small packets PVP test.
> > 
> > This patch improves the performance for small packets, and has
> > distinguished the packets by size. So although the performance
> > for big packets doesn't change, it makes it relatively easy to
> > do some special optimizations for the big packets too.
> > 
> > Signed-off-by: Tiwei Bie<tiwei.bie at intel.com>
> > Signed-off-by: Zhihong Wang<zhihong.wang at intel.com>
> > Signed-off-by: Zhiyong Yang<zhiyong.yang at intel.com>
> > ---
> > This optimization depends on the CPU internal pipeline design.
> > So further tests (e.g. ARM) from the community is appreciated.
> > 
> >   lib/librte_vhost/vhost.c      |   2 +-
> >   lib/librte_vhost/vhost.h      |  13 +++
> >   lib/librte_vhost/vhost_user.c |  12 +++
> >   lib/librte_vhost/virtio_net.c | 240 ++++++++++++++++++++++++++++++++----------
> >   4 files changed, 209 insertions(+), 58 deletions(-)
> 
> I did some PVP benchmark with your patch.
> First I tried my standard PVP setup, with io forwarding on host and
> macswap on guest in bidirectional mode.
> 
> With this, I notice no improvement (18.8Mpps), but I think it explains
> because guest is the bottleneck here.
> So I change my setup to do csum forwarding on host side, so that host's
> PMD threads are more loaded.
> 
> In this case, I notice a great improvement, I get 18.8Mpps with your
> patch instead of 14.8Mpps without! Great work!
> 
> Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> 

Thank you very much for taking time to review and test this patch! :-)

Best regards,
Tiwei Bie