From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH RFC] virtio_balloon: refill by config handler
Date: Tue, 5 Jan 2016 17:31:36 +0200
Message-ID: <20160105164041-mutt-send-email-mst__9717.91055421836$1452007918$gmane$org@redhat.com>
References: <1451643122-21561-1-git-send-email-mst@redhat.com>
	<20160105143733.GE3178@pathway.suse.cz>
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: <20160105143733.GE3178@pathway.suse.cz>
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: Petr Mladek <pmladek@suse.com>
Cc: Tejun Heo <tj@kernel.org>, Jiri Kosina <jkosina@suse.cz>, Jeff Epler <jepler@unpythonic.net>, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org
List-Id: virtualization@lists.linuxfoundation.org

On Tue, Jan 05, 2016 at 03:37:33PM +0100, Petr Mladek wrote:
> On Fri 2016-01-01 12:13:48, Michael S. Tsirkin wrote:
> > Peter Mladek reported that balloon might never refill completely after
> > restore.  This is because fill_balloon is only called once there.
> > Calling fill_balloon repeatedly seems too aggressive,
> > especially in light of the fact that it sleeps on failure: let's
> > wake the config change handler and fill it asynchronously.
> > 
> > Reported-by: Petr Mladek <pmladek@suse.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> > 
> > I was unable to test this - for some reason my test VM
> > doesn't resume (with or without the patch).
> > Petr, does this work for you?
> 
> Ah, I have just realized that the problem happens only after the
> conversion to the workqueue. It works without this patch with the
> current code. The balloon kthread is waken when released from
> __refrigerator().

In fact, maybe we should drop fill_balloon and
update_balloon_size here?
Resume will finish faster ...

> I am sorry for the noise. I wanted to split the conversion to
> workqueues into two patches to make it better readable. We need to
> queue the balloon resizing work here. I wrongly assumed that the
> original kthread must have the same problem.
> 
> Best Regards,
> Petr
> 
> >  drivers/virtio/virtio_balloon.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> > index 7efc329..ee29473 100644
> > --- a/drivers/virtio/virtio_balloon.c
> > +++ b/drivers/virtio/virtio_balloon.c
> > @@ -589,7 +589,7 @@ static int virtballoon_restore(struct virtio_device *vdev)
> >  
> >  	virtio_device_ready(vdev);
> >  
> > -	fill_balloon(vb, towards_target(vb));
> > +	wake_up(&vb->config_change);
> >  	update_balloon_size(vb);
> >  	return 0;
> >  }
> > -- 
> > MST