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Date: Wed, 12 Dec 2018 10:09:51 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: jiangyiwen <jiangyiwen@...wei.com>
Cc: Stefan Hajnoczi <stefanha@...hat.com>,
Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org,
kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 0/5] VSOCK: support mergeable rx buffer in vhost-vsock
On Wed, Dec 12, 2018 at 05:25:50PM +0800, jiangyiwen wrote:
> Now vsock only support send/receive small packet, it can't achieve
> high performance. As previous discussed with Jason Wang, I revisit the
> idea of vhost-net about mergeable rx buffer and implement the mergeable
> rx buffer in vhost-vsock, it can allow big packet to be scattered in
> into different buffers and improve performance obviously.
>
> This series of patches mainly did three things:
> - mergeable buffer implementation
> - increase the max send pkt size
> - add used and signal guest in a batch
>
> And I write a tool to test the vhost-vsock performance, mainly send big
> packet(64K) included guest->Host and Host->Guest. I test performance
> independently and the result as follows:
>
> Before performance:
> Single socket Multiple sockets(Max Bandwidth)
> Guest->Host ~400MB/s ~480MB/s
> Host->Guest ~1450MB/s ~1600MB/s
>
> After performance only use implement mergeable rx buffer:
> Single socket Multiple sockets(Max Bandwidth)
> Guest->Host ~400MB/s ~480MB/s
> Host->Guest ~1280MB/s ~1350MB/s
>
> In this case, max send pkt size is still limited to 4K, so Host->Guest
> performance will worse than before.
It's concerning though, what if application sends small packets?
What is the source of the slowdown? Do you know?
> After performance increase the max send pkt size to 64K:
> Single socket Multiple sockets(Max Bandwidth)
> Guest->Host ~1700MB/s ~2900MB/s
> Host->Guest ~1500MB/s ~2440MB/s
>
> After performance all patches are used:
> Single socket Multiple sockets(Max Bandwidth)
> Guest->Host ~1700MB/s ~2900MB/s
> Host->Guest ~1700MB/s ~2900MB/s
>
> >From the test results, the performance is improved obviously, and guest
> memory will not be wasted.
>
> In addition, in order to support mergeable rx buffer in virtio-vsock,
> we need to add a qemu patch to support parse feature.
>
> ---
> v1 -> v2:
> * Addressed comments from Jason Wang.
> * Add performance test result independently.
> * Use Skb_page_frag_refill() which can use high order page and reduce
> the stress of page allocator.
> * Still use fixed size(PAGE_SIZE) to fill rx buffer, because too small
> size can't fill one full packet, we only 128 vq num now.
> * Use iovec to replace buf in struct virtio_vsock_pkt, keep tx and rx
> consistency.
> * Add virtio_transport ops to get max pkt len, in order to be compatible
> with old version.
> ---
>
> Yiwen Jiang (5):
> VSOCK: support fill mergeable rx buffer in guest
> VSOCK: support fill data to mergeable rx buffer in host
> VSOCK: support receive mergeable rx buffer in guest
> VSOCK: increase send pkt len in mergeable mode to improve performance
> VSOCK: batch sending rx buffer to increase bandwidth
>
> drivers/vhost/vsock.c | 183 ++++++++++++++++++++-----
> include/linux/virtio_vsock.h | 13 +-
> include/uapi/linux/virtio_vsock.h | 5 +
> net/vmw_vsock/virtio_transport.c | 229 +++++++++++++++++++++++++++-----
> net/vmw_vsock/virtio_transport_common.c | 66 ++++++---
> 5 files changed, 411 insertions(+), 85 deletions(-)
>
> --
> 1.8.3.1
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