[dpdk-dev] [PATCH v7 0/7] vhost: optimize mergeable Rx path

[Yuanhan Liu]

Applied to dpdk-next-virtio.

And thanks for testing and reviewing.

	--yliu

On Fri, Oct 14, 2016 at 05:34:31PM +0800, Yuanhan Liu wrote:
> This is a new set of patches to optimize the mergeable Rx code path.
> No refactoring (rewrite) was made this time. It just applies some
> findings from Zhihong (kudos to him!) that could improve the mergeable
> Rx path on the old code.
> 
> The two major factors that could improve the performance greatly are:
> 
> - copy virtio header together with packet data. This could remove
>   the buubbles between the two copy to optimize the cache access.
> 
>   This is implemented in patch 2 "vhost: optimize cache access"
> 
> - shadow used ring update and update them at once
> 
>   The basic idea is to update used ring in a local buffer and flush
>   them to the virtio used ring at once in the end. Again, this is
>   for optimizing the cache access.
> 
>   This is implemented in patch 5 "vhost: shadow used ring update"
> 
> The two optimizations could yield 40+% performance in micro testing
> and 20+% in PVP case testing with 64B packet size.
> 
> Besides that, there are some tiny optimizations, such as prefetch
> avail ring (patch 6) and retrieve avail head once (patch 7).
> 
> Note: the shadow used ring tech could also be applied to the non-mrg
> Rx path (and even the dequeu) path. I didn't do that for two reasons:
> 
> - we already update used ring in batch in both path: it's not shadowed
>   first though.
> 
> - it's a bit too late too make many changes at this stage: RC1 is out. 
> 
> Please help testing.
> 
> Thanks.
> 
> 	--yliu
> 
> Cc: Jianbo Liu <jianbo.liu at linaro.org>
> ---
> Yuanhan Liu (4):
>   vhost: simplify mergeable Rx vring reservation
>   vhost: use last avail idx for avail ring reservation
>   vhost: prefetch avail ring
>   vhost: retrieve avail head once
> 
> Zhihong Wang (3):
>   vhost: remove useless volatile
>   vhost: optimize cache access
>   vhost: shadow used ring update
> 
>  lib/librte_vhost/vhost.c      |  13 ++-
>  lib/librte_vhost/vhost.h      |   5 +-
>  lib/librte_vhost/vhost_user.c |  23 +++--
>  lib/librte_vhost/virtio_net.c | 193 +++++++++++++++++++++++++-----------------
>  4 files changed, 149 insertions(+), 85 deletions(-)
> 
> -- 
> 1.9.0