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SubjectRe: [PATCH RFC 0/4] vsock/virtio: optimizations to increase the throughput
On Thu, Apr 04, 2019 at 12:58:34PM +0200, Stefano Garzarella wrote:
> This series tries to increase the throughput of virtio-vsock with slight
> changes:
> - patch 1/4: reduces the number of credit update messages sent to the
> transmitter
> - patch 2/4: allows the host to split packets on multiple buffers,
> in this way, we can remove the packet size limit to
> VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE
> - patch 3/4: uses VIRTIO_VSOCK_MAX_PKT_BUF_SIZE as the max packet size
> allowed
> - patch 4/4: increases RX buffer size to 64 KiB (affects only host->guest)
>
> RFC:
> - maybe patch 4 can be replaced with multiple queues with different
> buffer sizes or using EWMA to adapt the buffer size to the traffic
>
> - as Jason suggested in a previous thread [1] I'll evaluate to use
> virtio-net as transport, but I need to understand better how to
> interface with it, maybe introducing sk_buff in virtio-vsock.
>
> Any suggestions?
>
> Here some benchmarks step by step. I used iperf3 [2] modified with VSOCK
> support:
>
> host -> guest [Gbps]
> pkt_size before opt. patch 1 patches 2+3 patch 4
> 64 0.060 0.102 0.102 0.096
> 256 0.22 0.40 0.40 0.36
> 512 0.42 0.82 0.85 0.74
> 1K 0.7 1.6 1.6 1.5
> 2K 1.5 3.0 3.1 2.9
> 4K 2.5 5.2 5.3 5.3
> 8K 3.9 8.4 8.6 8.8
> 16K 6.6 11.1 11.3 12.8
> 32K 9.9 15.8 15.8 18.1
> 64K 13.5 17.4 17.7 21.4
> 128K 17.9 19.0 19.0 23.6
> 256K 18.0 19.4 19.8 24.4
> 512K 18.4 19.6 20.1 25.3
>
> guest -> host [Gbps]
> pkt_size before opt. patch 1 patches 2+3
> 64 0.088 0.100 0.101
> 256 0.35 0.36 0.41
> 512 0.70 0.74 0.73
> 1K 1.1 1.3 1.3
> 2K 2.4 2.4 2.6
> 4K 4.3 4.3 4.5
> 8K 7.3 7.4 7.6
> 16K 9.2 9.6 11.1
> 32K 8.3 8.9 18.1
> 64K 8.3 8.9 25.4
> 128K 7.2 8.7 26.7
> 256K 7.7 8.4 24.9
> 512K 7.7 8.5 25.0
>
> Thanks,
> Stefano

I simply love it that you have analysed the individual impact of
each patch! Great job!

For comparison's sake, it could be IMHO benefitial to add a column
with virtio-net+vhost-net performance.

This will both give us an idea about whether the vsock layer introduces
inefficiencies, and whether the virtio-net idea has merit.

One other comment: it makes sense to test with disabling smap
mitigations (boot host and guest with nosmap). No problem with also
testing the default smap path, but I think you will discover that the
performance impact of smap hardening being enabled is often severe for
such benchmarks.


> [1] https://www.spinics.net/lists/netdev/msg531783.html
> [2] https://github.com/stefano-garzarella/iperf/
>
> Stefano Garzarella (4):
> vsock/virtio: reduce credit update messages
> vhost/vsock: split packets to send using multiple buffers
> vsock/virtio: change the maximum packet size allowed
> vsock/virtio: increase RX buffer size to 64 KiB
>
> drivers/vhost/vsock.c | 35 ++++++++++++++++++++-----
> include/linux/virtio_vsock.h | 3 ++-
> net/vmw_vsock/virtio_transport_common.c | 18 +++++++++----
> 3 files changed, 44 insertions(+), 12 deletions(-)
>
> --
> 2.20.1

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