On 2018年01月29日 22:11, Jens Freimann wrote:
This is a basic implementation of packed virtqueues as specified in the
Virtio 1.1 draft. A compiled version of the current draft is available
at https://github.com/oasis-tcs/virtio-docs.git (or as .pdf at
https://github.com/oasis-tcs/virtio-docs/blob/master/virtio-v1.1-packed-wd07.pdf
It does not implement yet indirect descriptors and checksum offloading.
VIRTIO_F_IN_ORER is not implemented, as well as support for mergeable buffers
with packed queues. Patches for this will follow soon.
A packed virtqueue is different from a split virtqueue in that it
consists of only a single descriptor ring that replaces available and
used ring, index and descriptor buffer.
Each descriptor is readable and writable and has a flags field. These flags
will mark if a descriptor is available or used. To detect new available
descriptors
even after the ring has wrapped, device and driver each have a
single-bit wrap counter that is flipped from 0 to 1 and vice versa every time
the last descriptor in the ring is used/made available.
The idea behind this is to 1. improve performance by avoiding cache misses
and 2. be easier for devices to implement.
Regarding performance: with these patches I get 21.13 Mpps on my system
as compared to 18.8 Mpps with the virtio 1.0 code. Packet size was 64
bytes, 0.05% acceptable loss. Test setup is described as in
http://dpdk.org/doc/guides/howto/pvp_reference_benchmark.html
Packet generator:
MoonGen
Intel(R) Xeon(R) CPU E5-2665 0 @ 2.40GHz
Intel X710 NIC
RHEL 7.4
Device under test:
Intel(R) Xeon(R) CPU E5-2667 v4 @ 3.20GHz
Intel X710 NIC
RHEL 7.4
VM on DuT: RHEL7.4
I plan to do more performance test with bigger frame sizes.
This patch series is based on a prototype implemented by Yuanhan Liu and
Tiwei Bie.
Hi Jens:
May I ask how do you test the patch? I believe you need some basic
packed ring support in both qemu and vhost-user protocol.
Thanks
