From: "Michael S. Tsirkin" <mst@redhat.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: dev@dpdk.org, i.maximets@samsung.com, tiwei.bie@intel.com,
zhihong.wang@intel.com, jasowang@redhat.com, stable@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2 4/4] vhost: remove useless prefetch for packed ring descriptor
Date: Wed, 19 Dec 2018 10:49:38 -0500 [thread overview]
Message-ID: <20181219104840-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20181219082113.24455-5-maxime.coquelin@redhat.com>
On Wed, Dec 19, 2018 at 09:21:13AM +0100, Maxime Coquelin wrote:
> This prefetch does not show any performance improvement.
>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Likely because of the RMB.
Try prefetching the *next* descriptor maybe?
> ---
> lib/librte_vhost/virtio_net.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index a9be633de..4d201a3fd 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -1437,8 +1437,6 @@ virtio_dev_tx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
> {
> uint16_t i;
>
> - rte_prefetch0(&vq->desc_packed[vq->last_avail_idx]);
> -
> if (unlikely(dev->dequeue_zero_copy)) {
> struct zcopy_mbuf *zmbuf, *next;
>
> --
> 2.17.2
next prev parent reply other threads:[~2018-12-19 15:49 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-19 8:21 [dpdk-dev] [PATCH v2 0/4] vhost: add missing barriers, move prefetching Maxime Coquelin
2018-12-19 8:21 ` [dpdk-dev] [PATCH v2 1/4] vhost: enforce avail index and desc read ordering Maxime Coquelin
2018-12-19 15:47 ` Michael S. Tsirkin
2018-12-19 15:50 ` Maxime Coquelin
2018-12-19 8:21 ` [dpdk-dev] [PATCH v2 2/4] vhost: enforce desc flags and content " Maxime Coquelin
2018-12-19 8:21 ` [dpdk-dev] [PATCH v2 3/4] vhost: prefetch descriptor after the read barrier Maxime Coquelin
2018-12-19 8:21 ` [dpdk-dev] [PATCH v2 4/4] vhost: remove useless prefetch for packed ring descriptor Maxime Coquelin
2018-12-19 15:49 ` Michael S. Tsirkin [this message]
2018-12-19 15:50 ` [dpdk-dev] [PATCH v2 0/4] vhost: add missing barriers, move prefetching Michael S. Tsirkin
2018-12-19 16:28 ` Ilya Maximets
2018-12-20 4:39 ` Tiwei Bie
2018-12-20 18:19 ` Maxime Coquelin
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