[dpdk-dev] [PATCH v5 0/6] vhost: optimize enqueue

[Maxime Coquelin]

Hi,

On 09/09/2016 05:39 AM, Zhihong Wang wrote:
> This patch set optimizes the vhost enqueue function.
>
> It implements the vhost logic from scratch into a single function designed
> for high performance and good maintainability, and improves CPU efficiency
> significantly by optimizing cache access, which means:
>
>  *  Higher maximum throughput can be achieved for fast frontends like DPDK
>     virtio pmd.
>
>  *  Better scalability can be achieved that each vhost core can support
>     more connections because it takes less cycles to handle each single
>     frontend.
>
> This patch set contains:
>
>  1. A Windows VM compatibility fix for vhost enqueue in 16.07 release.
>
>  2. A baseline patch to rewrite the vhost logic.
>
>  3. A series of optimization patches added upon the baseline.
>
> The main optimization techniques are:
>
>  1. Reorder code to reduce CPU pipeline stall cycles.
>
>  2. Batch update the used ring for better efficiency.
>
>  3. Prefetch descriptor to hide cache latency.
>
>  4. Remove useless volatile attribute to allow compiler optimization.
>
> Code reordering and batch used ring update bring most of the performance
> improvements.
>
> In the existing code there're 2 callbacks for vhost enqueue:
>
>  *  virtio_dev_merge_rx for mrg_rxbuf turned on cases.
>
>  *  virtio_dev_rx for mrg_rxbuf turned off cases.
>
> The performance of the existing code is not optimal, especially when the
> mrg_rxbuf feature turned on. Besides, having 2 callback paths increases
> maintenance efforts.
>
> Also, there's a compatibility issue in the existing code which causes
> Windows VM to hang when the mrg_rxbuf feature turned on.
>
> ---
> Changes in v5:
>
>  1. Rebase to the latest branch.
>
>  2. Rename variables to keep consistent in naming style.
>
>  3. Small changes like return value adjustment and vertical alignment.
>
>  4. Add details in commit log.
Just tried to apply your series without success.
Apparently, it is not based directly on master branch,
as it lacks some SHA-1 information.

Could you rebase it against master please?

Thanks,
Maxime