From: "Michael S. Tsirkin" <mst@redhat.com>
To: Stefano Garzarella <sgarzare@redhat.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Stefan Hajnoczi <stefanha@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
virtualization@lists.linux-foundation.org,
Jason Wang <jasowang@redhat.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH v4 2/5] vsock/virtio: reduce credit update messages
Date: Tue, 3 Sep 2019 00:38:02 -0400 [thread overview]
Message-ID: <20190903003050-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20190717113030.163499-3-sgarzare@redhat.com>
On Wed, Jul 17, 2019 at 01:30:27PM +0200, Stefano Garzarella wrote:
> In order to reduce the number of credit update messages,
> we send them only when the space available seen by the
> transmitter is less than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE.
>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
> include/linux/virtio_vsock.h | 1 +
> net/vmw_vsock/virtio_transport_common.c | 16 +++++++++++++---
> 2 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
> index 7d973903f52e..49fc9d20bc43 100644
> --- a/include/linux/virtio_vsock.h
> +++ b/include/linux/virtio_vsock.h
> @@ -41,6 +41,7 @@ struct virtio_vsock_sock {
>
> /* Protected by rx_lock */
> u32 fwd_cnt;
> + u32 last_fwd_cnt;
> u32 rx_bytes;
> struct list_head rx_queue;
> };
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index 095221f94786..a85559d4d974 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -211,6 +211,7 @@ static void virtio_transport_dec_rx_pkt(struct virtio_vsock_sock *vvs,
> void virtio_transport_inc_tx_pkt(struct virtio_vsock_sock *vvs, struct virtio_vsock_pkt *pkt)
> {
> spin_lock_bh(&vvs->tx_lock);
> + vvs->last_fwd_cnt = vvs->fwd_cnt;
> pkt->hdr.fwd_cnt = cpu_to_le32(vvs->fwd_cnt);
> pkt->hdr.buf_alloc = cpu_to_le32(vvs->buf_alloc);
> spin_unlock_bh(&vvs->tx_lock);
> @@ -261,6 +262,7 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> struct virtio_vsock_sock *vvs = vsk->trans;
> struct virtio_vsock_pkt *pkt;
> size_t bytes, total = 0;
> + u32 free_space;
> int err = -EFAULT;
>
> spin_lock_bh(&vvs->rx_lock);
> @@ -291,11 +293,19 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> virtio_transport_free_pkt(pkt);
> }
> }
> +
> + free_space = vvs->buf_alloc - (vvs->fwd_cnt - vvs->last_fwd_cnt);
> +
> spin_unlock_bh(&vvs->rx_lock);
>
> - /* Send a credit pkt to peer */
> - virtio_transport_send_credit_update(vsk, VIRTIO_VSOCK_TYPE_STREAM,
> - NULL);
> + /* We send a credit update only when the space available seen
> + * by the transmitter is less than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE
This is just repeating what code does though.
Please include the *reason* for the condition.
E.g. here's a better comment:
/* To reduce number of credit update messages,
* don't update credits as long as lots of space is available.
* Note: the limit chosen here is arbitrary. Setting the limit
* too high causes extra messages. Too low causes transmitter
* stalls. As stalls are in theory more expensive than extra
* messages, we set the limit to a high value. TODO: experiment
* with different values.
*/
> + */
> + if (free_space < VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
> + virtio_transport_send_credit_update(vsk,
> + VIRTIO_VSOCK_TYPE_STREAM,
> + NULL);
> + }
>
> return total;
>
> --
> 2.20.1
next prev parent reply other threads:[~2019-09-03 4:38 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 11:30 [PATCH v4 0/5] vsock/virtio: optimizations to increase the throughput Stefano Garzarella
2019-07-17 11:30 ` [PATCH v4 1/5] vsock/virtio: limit the memory used per-socket Stefano Garzarella
2019-07-29 14:04 ` Michael S. Tsirkin
2019-07-29 15:36 ` Stefano Garzarella
2019-07-29 15:49 ` Michael S. Tsirkin
2019-07-29 16:19 ` Stefano Garzarella
2019-07-29 16:50 ` Stefano Garzarella
2019-07-29 19:10 ` Michael S. Tsirkin
2019-07-30 9:35 ` Stefano Garzarella
2019-07-30 20:42 ` Michael S. Tsirkin
2019-08-01 10:47 ` Stefano Garzarella
2019-08-01 13:21 ` Michael S. Tsirkin
2019-08-01 13:36 ` Stefano Garzarella
2019-09-01 8:26 ` Michael S. Tsirkin
2019-09-01 10:17 ` Michael S. Tsirkin
2019-09-02 9:57 ` Stefano Garzarella
2019-09-02 15:23 ` Michael S. Tsirkin
2019-09-03 4:39 ` Michael S. Tsirkin
2019-09-03 7:45 ` Stefano Garzarella
2019-09-03 7:52 ` Michael S. Tsirkin
2019-09-03 8:00 ` Stefano Garzarella
2019-07-29 16:01 ` Michael S. Tsirkin
2019-07-29 16:41 ` Stefano Garzarella
2019-07-29 19:33 ` Michael S. Tsirkin
2019-08-30 9:40 ` Stefano Garzarella
2019-09-01 6:56 ` Michael S. Tsirkin
2019-09-02 8:39 ` Stefan Hajnoczi
2019-09-02 8:55 ` Stefano Garzarella
2019-10-11 13:40 ` Stefano Garzarella
2019-10-11 14:11 ` Michael S. Tsirkin
2019-10-11 14:23 ` Stefano Garzarella
2019-10-14 8:17 ` Stefan Hajnoczi
2019-10-14 8:21 ` Jason Wang
2019-10-14 8:38 ` Stefano Garzarella
2019-07-17 11:30 ` [PATCH v4 2/5] vsock/virtio: reduce credit update messages Stefano Garzarella
2019-07-22 8:36 ` Stefan Hajnoczi
2019-09-03 4:38 ` Michael S. Tsirkin [this message]
2019-09-03 7:31 ` Stefano Garzarella
2019-09-03 7:38 ` Michael S. Tsirkin
2019-07-17 11:30 ` [PATCH v4 3/5] vsock/virtio: fix locking in virtio_transport_inc_tx_pkt() Stefano Garzarella
2019-07-17 14:51 ` Michael S. Tsirkin
2019-07-18 7:43 ` Stefano Garzarella
2019-07-22 8:53 ` Stefan Hajnoczi
2019-07-17 11:30 ` [PATCH v4 4/5] vhost/vsock: split packets to send using multiple buffers Stefano Garzarella
2019-07-17 14:54 ` Michael S. Tsirkin
2019-07-18 7:50 ` Stefano Garzarella
2019-07-18 8:13 ` Michael S. Tsirkin
2019-07-18 9:37 ` Stefano Garzarella
2019-07-18 11:35 ` Michael S. Tsirkin
2019-07-19 8:08 ` Stefano Garzarella
2019-07-19 8:21 ` Jason Wang
2019-07-19 8:39 ` Stefano Garzarella
2019-07-19 8:51 ` Jason Wang
2019-07-19 9:20 ` Stefano Garzarella
2019-07-22 9:06 ` Stefan Hajnoczi
2019-07-17 11:30 ` [PATCH v4 5/5] vsock/virtio: change the maximum packet size allowed Stefano Garzarella
2019-07-17 14:59 ` Michael S. Tsirkin
2019-07-18 7:52 ` Stefano Garzarella
2019-07-18 12:33 ` Michael S. Tsirkin
2019-07-19 8:29 ` Stefano Garzarella
2019-07-22 9:07 ` Stefan Hajnoczi
2019-07-22 9:08 ` [PATCH v4 0/5] vsock/virtio: optimizations to increase the throughput Stefan Hajnoczi
2019-07-22 9:14 ` Stefano Garzarella
2019-07-29 13:12 ` Stefan Hajnoczi
2019-07-29 13:59 ` Michael S. Tsirkin
2019-07-30 9:40 ` Stefano Garzarella
2019-07-30 10:03 ` Jason Wang
2019-07-30 15:38 ` Stefano Garzarella
2019-09-03 8:02 ` request for stable (was Re: [PATCH v4 0/5] vsock/virtio: optimizations to increase the throughput) Michael S. Tsirkin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190903003050-mutt-send-email-mst@kernel.org \
--to=mst@redhat.com \
--cc=davem@davemloft.net \
--cc=jasowang@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=sgarzare@redhat.com \
--cc=stefanha@redhat.com \
--cc=virtualization@lists.linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).