From: Jens Freimann <jfreimann@redhat.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: dev@dpdk.org, tiwei.bie@intel.com, zhihong.wang@intel.com,
stable@dpdk.org
Subject: Re: [dpdk-dev] [dpdk-stable] [PATCH v2] vhost: avoid memory barriers when no descriptors dequeued
Date: Tue, 23 Oct 2018 14:39:03 +0200 [thread overview]
Message-ID: <20181023123903.dagzx72lrs2guwhv@jenstp.localdomain> (raw)
In-Reply-To: <20181023100710.14739-1-maxime.coquelin@redhat.com>
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@redhat.com>
Tested-by: Jens Freimann <jfreimann@redhat.com>
regards,
Jens
next prev parent reply other threads:[~2018-10-23 12:39 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-23 10:07 [dpdk-dev] " Maxime Coquelin
2018-10-23 12:39 ` Jens Freimann [this message]
2018-10-24 8:50 ` Tiwei Bie
2018-10-24 10:51 ` Maxime Coquelin
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