Re: [dpdk-dev] [PATCH v4] vhost: Add indirect descriptors support to the TX path

["Wang, Zhihong" <zhihong.wang@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Wang, Zhihong
> Sent: Friday, October 14, 2016 3:25 PM
> To: Maxime Coquelin <maxime.coquelin@redhat.com>;
> yuanhan.liu@linux.intel.com; Xie, Huawei <huawei.xie@intel.com>;
> dev@dpdk.org
> Cc: vkaplans@redhat.com; mst@redhat.com;
> stephen@networkplumber.org
> Subject: Re: [dpdk-dev] [PATCH v4] vhost: Add indirect descriptors support
> to the TX path
> 
> 
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Maxime Coquelin
> > Sent: Tuesday, September 27, 2016 4:43 PM
> > To: yuanhan.liu@linux.intel.com; Xie, Huawei <huawei.xie@intel.com>;
> > dev@dpdk.org
> > Cc: vkaplans@redhat.com; mst@redhat.com;
> > stephen@networkplumber.org; Maxime Coquelin
> > <maxime.coquelin@redhat.com>
> > Subject: [dpdk-dev] [PATCH v4] vhost: Add indirect descriptors support to
> > the TX path
> >
> > Indirect descriptors are usually supported by virtio-net devices,
> > allowing to dispatch a larger number of requests.
> >
> > When the virtio device sends a packet using indirect descriptors,
> > only one slot is used in the ring, even for large packets.
> >
> > The main effect is to improve the 0% packet loss benchmark.
> > A PVP benchmark using Moongen (64 bytes) on the TE, and testpmd
> > (fwd io for host, macswap for VM) on DUT shows a +50% gain for
> > zero loss.
> >
> > On the downside, micro-benchmark using testpmd txonly in VM and
> > rxonly on host shows a loss between 1 and 4%.i But depending on
> > the needs, feature can be disabled at VM boot time by passing
> > indirect_desc=off argument to vhost-user device in Qemu.
> >
> > Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> 
> 
> Hi Maxime,
> 
> Seems this patch can't with Windows virtio guest in my test.
> Have you done similar tests before?
> 
> The way I test:
> 
>  1. Make sure https://patchwork.codeaurora.org/patch/84339/ is applied
> 
>  2. Start testpmd with iofwd between 2 vhost ports
> 
>  3. Start 2 Windows guests connected to the 2 vhost ports

The mrg_rxbuf feature is on.

> 
>  4. Disable firewall and assign IP to each guest using ipconfig
> 
>  5. Use ping to test connectivity
> 
> When I disable this patch by setting:
> 
>     0ULL << VIRTIO_RING_F_INDIRECT_DESC,
> 
> the connection is fine, but when I restore:
> 
>     1ULL << VIRTIO_RING_F_INDIRECT_DESC,
> 
> the connection is broken.
> 
> 
> Thanks
> Zhihong
>