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 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

 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