From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37592) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VEEJ5-0003Jh-3C for qemu-devel@nongnu.org; Tue, 27 Aug 2013 04:07:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VEEIx-0007rV-Sb for qemu-devel@nongnu.org; Tue, 27 Aug 2013 04:07:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57617) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VEEIx-0007rH-Ks for qemu-devel@nongnu.org; Tue, 27 Aug 2013 04:07:11 -0400 Date: Tue, 27 Aug 2013 09:06:57 +0100 From: "Richard W.M. Jones" Message-ID: <20130827080657.GA19187@redhat.com> References: <1377187852-11192-1-git-send-email-pbonzini@redhat.com> <87mwo9smjf.fsf@codemonkey.ws> <52164FFD.5030101@redhat.com> <521663A9.6040207@redhat.com> <87eh9lqyhp.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87eh9lqyhp.fsf@codemonkey.ws> Subject: Re: [Qemu-devel] pvpanic plans? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: pkrempa@redhat.com, marcel.a@redhat.com, libvir-list@redhat.com, hutao@cn.fujitsu.com, mst@redhat.com, qemu-devel@nongnu.org, armbru@redhat.com, rhod@redhat.com, kraxel@redhat.com, Paolo Bonzini , lcapitulino@redhat.com, Laszlo Ersek , afaerber@suse.de On Thu, Aug 22, 2013 at 03:09:06PM -0500, Anthony Liguori wrote: > Paolo Bonzini writes: > > Also, a virtio watchdog device makes little sense, IMHO. PV makes sense > > if emulation has insufficient performance, excessive CPU usage, or > > excessive complexity. We already have both an ISA and a PCI watchdog, > > and they serve their purpose wonderfully. > > Neither of which actually work with modern versions of Windows FWIW. Correct, although someone could write a driver! > Plus emulated watchdogs do not take into account steal time or > overcommit in general. I've seen multiple cases where a naive watchdog > has a problem in the field when the system is under heavy load. The watchdog devices in qemu run on guest time. However the watchdog *daemon* inside the guest probably does behave badly as you describe. Changing the device model isn't going to help this, but it would definitely make sense to fix the daemon (although I don't know how -- is steal time exposed to guests?) I don't necessarily think a virtio-watchdog is a bad idea. For one thing it'd mean we would have a watchdog device that works on ARM. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top