On Tue, Oct 23, 2018 at 12:07:10PM +0200, Maxime Coquelin wrote:
In both split and packed dequeue paths, flush_shadow_used_ring
and vhost_ring_call variants gets called even if not packets
have been dequeued, and so no descriptors updates happened.
It has an impact on CPU pipeline, as memory barriers are used
in these functions.
This patch don't call these functions if no descriptors have
been dequeued. The performance gain with split ring when
dequeue zero-copy is disabled should be null, but should be
noticeable with packed ring or dequeue zero-copy enabled.
I tried this with packed ring pmd patch series v8 and it works fine.
It doesn't hurt performance either, I see improvements in sending
packets from guest to host.
Reviewed-by: Jens Freimann <[email protected]>
Tested-by: Jens Freimann <[email protected]>
regards,
Jens
