From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH v4 4/5] vhost/vsock: split packets to send using multiple
	buffers
Date: Thu, 18 Jul 2019 04:13:26 -0400
Message-ID: <20190718041234-mutt-send-email-mst__2606.23038500256$1563437639$gmane$org@kernel.org>
References: <20190717113030.163499-1-sgarzare@redhat.com>
	<20190717113030.163499-5-sgarzare@redhat.com>
	<20190717105336-mutt-send-email-mst@kernel.org>
	<CAGxU2F45v40qAOHkm1Hk2E69gCS0UwVgS5NS+tDXXuzdF4EixA@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <virtualization-bounces@lists.linux-foundation.org>
Content-Disposition: inline
In-Reply-To: <CAGxU2F45v40qAOHkm1Hk2E69gCS0UwVgS5NS+tDXXuzdF4EixA@mail.gmail.com>
List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/virtualization>,
	<mailto:virtualization-request@lists.linux-foundation.org?subject=unsubscribe>
List-Archive: <http://lists.linuxfoundation.org/pipermail/virtualization/>
List-Post: <mailto:virtualization@lists.linux-foundation.org>
List-Help: <mailto:virtualization-request@lists.linux-foundation.org?subject=help>
List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/virtualization>,
	<mailto:virtualization-request@lists.linux-foundation.org?subject=subscribe>
Sender: virtualization-bounces@lists.linux-foundation.org
Errors-To: virtualization-bounces@lists.linux-foundation.org
To: Stefano Garzarella <sgarzare@redhat.com>
Cc: kvm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Stefan Hajnoczi <stefanha@redhat.com>, "David S. Miller" <davem@davemloft.net>
List-Id: virtualization@lists.linuxfoundation.org

On Thu, Jul 18, 2019 at 09:50:14AM +0200, Stefano Garzarella wrote:
> On Wed, Jul 17, 2019 at 4:55 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Wed, Jul 17, 2019 at 01:30:29PM +0200, Stefano Garzarella wrote:
> > > If the packets to sent to the guest are bigger than the buffer
> > > available, we can split them, using multiple buffers and fixing
> > > the length in the packet header.
> > > This is safe since virtio-vsock supports only stream sockets.
> > >
> > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> >
> > So how does it work right now? If an app
> > does sendmsg with a 64K buffer and the other
> > side publishes 4K buffers - does it just stall?
> 
> Before this series, the 64K (or bigger) user messages was split in 4K packets
> (fixed in the code) and queued in an internal list for the TX worker.
> 
> After this series, we will queue up to 64K packets and then it will be split in
> the TX worker, depending on the size of the buffers available in the
> vring. (The idea was to allow EWMA or a configuration of the buffers size, but
> for now we postponed it)

Got it. Using workers for xmit is IMHO a bad idea btw.
Why is it done like this?

> Note: virtio-vsock only supports stream socket for now.
> 
> Thanks,
> Stefano