From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [PATCH 18/31] virtio: console: Buffer data that comes from the host Date: Thu, 14 Jan 2010 09:45:12 +1030 Message-ID: <201001140945.12345.rusty@rustcorp.com.au> References: <1261492481-19817-1-git-send-email-amit.shah@redhat.com> <201001132143.32464.rusty@rustcorp.com.au> <20100113112452.GA24002@amit-x200.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100113112452.GA24002@amit-x200.redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Amit Shah Cc: virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On Wed, 13 Jan 2010 09:54:52 pm Amit Shah wrote: > On (Wed) Jan 13 2010 [21:43:32], Rusty Russell wrote: > > On Wed, 13 Jan 2010 04:41:48 pm Amit Shah wrote: > > > On (Mon) Jan 04 2010 [15:17:17], Amit Shah wrote: > > > > On (Mon) Jan 04 2010 [19:45:30], Rusty Russell wrote: > > > > > On Wed, 23 Dec 2009 01:04:28 am Amit Shah wrote: > > > > > > The console could be flooded with data from the host; handle this > > > > > > situation by buffering the data. > > > > > > > > > > Is this still true? If we only add_buf when we're ready, surely the host > > > > > can't flood us with one virtqueue per port? > > > > > > > > I guess I meant something completely different. This message is > > > > definitely misleading and I'll re-word it. > > > > > > > > You're right; we don't need the 'guest throttling' feature that was > > > > needed earlier. > > > > > > BTW I meant this series doesn't have the guest throttling feature. > > > > > > Rusty, did you just have this comment for the series? If yes, I'll just > > > re-send this patch with a fixed description. > > > > I don't see why we ever allocate more than one incoming buffer though? > > To prevent against a fast host app sending data to a slow guest > consumer. > > Also, we use the in_vq for the buffering, so the number of buffers is > limited by the queue size that's declared by the host. But if the guest only ever registers one input buffer at a time, we get the same effect. And it means we use less memory. And our code is simpler. Similar with output. Cheers, Rusty.