[dpdk-dev] [PATCH v6 6/6] vhost: optimize cache access

[Maxime Coquelin]

On 09/20/2016 04:00 AM, Zhihong Wang wrote:
> This patch reorders the code to delay virtio header write to improve
> cache access efficiency for cases where the mrg_rxbuf feature is turned
> on. CPU pipeline stall cycles can be significantly reduced.
>
> Virtio header write and mbuf data copy are all remote store operations
> which takes a long time to finish. It's a good idea to put them together
> to remove bubbles in between, to let as many remote store instructions
> as possible go into store buffer at the same time to hide latency, and
> to let the H/W prefetcher goes to work as early as possible.
>
> On a Haswell machine, about 100 cycles can be saved per packet by this
> patch alone. Taking 64B packets traffic for example, this means about 60%
> efficiency improvement for the enqueue operation.

Thanks for the detailed information, I appreciate it.

Maxime