[dpdk-dev] [dpdk-stable] [PATCH v2] vhost: avoid memory barriers when no descriptors dequeued
Jens Freimann
jfreimann at redhat.com
Tue Oct 23 14:39:03 CEST 2018
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 <jfreimann at redhat.com>
Tested-by: Jens Freimann <jfreimann at redhat.com>
regards,
Jens
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