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References: <20220817135718.2553-1-qtxuning1999@sjtu.edu.cn> <20220817135718.2553-4-qtxuning1999@sjtu.edu.cn>
In-Reply-To: <20220817135718.2553-4-qtxuning1999@sjtu.edu.cn>
From:   Eugenio Perez Martin <eperezma@redhat.com>
Date:   Thu, 18 Aug 2022 08:19:29 +0200
Message-ID: <CAJaqyWeCYHvKShyQu0JEfLi=N+TLXdHQtt-VJR-4eVyU0MzT+w@mail.gmail.com>
Subject: Re: [RFC v2 3/7] vsock: batch buffers in tx
To:     Guo Zhi <qtxuning1999@sjtu.edu.cn>
Cc:     Jason Wang <jasowang@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        Michael Tsirkin <mst@redhat.com>,
        netdev <netdev@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        kvm list <kvm@vger.kernel.org>,
        virtualization <virtualization@lists.linux-foundation.org>
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On Wed, Aug 17, 2022 at 3:58 PM Guo Zhi <qtxuning1999@sjtu.edu.cn> wrote:
>
> Vsock uses buffers in order, and for tx driver doesn't have to
> know the length of the buffer. So we can do a batch for vsock if
> in order negotiated, only write one used ring for a batch of buffers
>
> Signed-off-by: Guo Zhi <qtxuning1999@sjtu.edu.cn>
> ---
>  drivers/vhost/vsock.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 368330417bde..b0108009c39a 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -500,6 +500,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
>         int head, pkts = 0, total_len = 0;
>         unsigned int out, in;
>         bool added = false;
> +       int last_head = -1;
>
>         mutex_lock(&vq->mutex);
>
> @@ -551,10 +552,16 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
>                 else
>                         virtio_transport_free_pkt(pkt);
>
> -               vhost_add_used(vq, head, 0);
> +               if (!vhost_has_feature(vq, VIRTIO_F_IN_ORDER))
> +                       vhost_add_used(vq, head, 0);
> +               else
> +                       last_head = head;
>                 added = true;
>         } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
>
> +       /* If in order feature negotiaged, we can do a batch to increase performance */
> +       if (vhost_has_feature(vq, VIRTIO_F_IN_ORDER) && last_head != -1)
> +               vhost_add_used(vq, last_head, 0);

Expanding my previous mail on patch 1, you can also use this in vsock
tx queue code. This way, no modifications to vhost.c functions are
needed.

Thanks!

>  no_more_replies:
>         if (added)
>                 vhost_signal(&vsock->dev, vq);
> --
> 2.17.1
>