On 2017年05月18日 11:03, Wei Wang wrote:
On 05/17/2017 02:22 PM, Jason Wang wrote:
On 2017年05月17日 14:16, Jason Wang wrote:
On 2017年05月16日 15:12, Wei Wang wrote:
Hi:
Care to post the driver codes too?
OK. It may take some time to clean up the driver code before post
it out. You can first
have a check of the draft at the repo here:
https://github.com/wei-w-wang/vhost-pci-driver
Best,
Wei
Interesting, looks like there's one copy on tx side. We used to have
zerocopy support for tun for VM2VM traffic. Could you please try to
compare it with your vhost-pci-net by:
We can analyze from the whole data path - from VM1's network stack to
send packets -> VM2's
network stack to receive packets. The number of copies are actually
the same for both.
That's why I'm asking you to compare the performance. The only reason
for vhost-pci is performance. You should prove it.
vhost-pci: 1-copy happen in VM1's driver xmit(), which copes packets
from its network stack to VM2's
RX ring buffer. (we call it "zerocopy" because there is no
intermediate copy between VMs)
zerocopy enabled vhost-net: 1-copy happen in tun's recvmsg, which
copies packets from VM1's TX ring
buffer to VM2's RX ring buffer.
Actually, there's a major difference here. You do copy in guest which
consumes time slice of vcpu thread on host. Vhost_net do this in its own
thread. So I feel vhost_net is even faster here, maybe I was wrong.
That being said, we compared to vhost-user, instead of vhost_net,
because vhost-user is the one
that is used in NFV, which we think is a major use case for vhost-pci.
If this is true, why not draft a pmd driver instead of a kernel one? And
do you use virtio-net kernel driver to compare the performance? If yes,
has OVS dpdk optimized for kernel driver (I think not)?
What's more important, if vhost-pci is faster, I think its kernel driver
should be also faster than virtio-net, no?
- make sure zerocopy is enabled for vhost_net
- comment skb_orphan_frags() in tun_net_xmit()
Thanks
You can even enable tx batching for tun by ethtool -C tap0 rx-frames
N. This will greatly improve the performance according to my test.
Thanks, but would this hurt latency?
Best,
Wei
I don't see this in my test.
Thanks
