From: Stefano Garzarella <sgarzare@redhat.com>
To: "Michael S. Tsirkin" <mst@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 09:31:20 +0200 [thread overview]
Message-ID: <20190903073120.kefllalytkvidcvh@steredhat> (raw)
In-Reply-To: <20190903003050-mutt-send-email-mst@kernel.org>
On Tue, Sep 03, 2019 at 12:38:02AM -0400, Michael S. Tsirkin wrote:
> 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.
> */
>
Yes, it is better, sorry for that. I'll try to avoid unnecessary comments,
explaining the reason for certain changes.
Since this patch is already queued in net-next, should I send another
patch to fix the comment?
Thanks,
Stefano
next prev parent reply other threads:[~2019-09-03 7:31 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
2019-09-03 7:31 ` Stefano Garzarella [this message]
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
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