From: Tiwei Bie <tiwei.bie@intel.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: dev@dpdk.org, jfreimann@redhat.com, zhihong.wang@intel.com,
stable@dpdk.org
Subject: Re: [PATCH v2] vhost: avoid memory barriers when no descriptors dequeued
Date: Wed, 24 Oct 2018 16:50:24 +0800 [thread overview]
Message-ID: <20181024085024.GA4708@debian> (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.
>
> Fixes: ae999ce49dcb ("vhost: add Tx support for packed ring")
> Fixes: 915cf9404225 ("vhost: use shadow used ring in dequeue path")
> Cc: stable@dpdk.org
>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>
> Changes in v2:
> - Fix shadow_used_idx reset in error path (Tiwei)
>
> lib/librte_vhost/virtio_net.c | 24 ++++++++++++++++--------
> 1 file changed, 16 insertions(+), 8 deletions(-)
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>
next prev parent reply other threads:[~2018-10-24 8:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-23 10:07 [PATCH v2] vhost: avoid memory barriers when no descriptors dequeued Maxime Coquelin
2018-10-23 12:39 ` [dpdk-stable] " Jens Freimann
2018-10-24 8:50 ` Tiwei Bie [this message]
2018-10-24 10:51 ` Maxime Coquelin
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