From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Kz4wR-0007R8-Bu for qemu-devel@nongnu.org; Sun, 09 Nov 2008 02:42:39 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Kz4wP-0007Qw-7Q for qemu-devel@nongnu.org; Sun, 09 Nov 2008 02:42:38 -0500 Received: from [199.232.76.173] (port=45968 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Kz4wP-0007Qt-2T for qemu-devel@nongnu.org; Sun, 09 Nov 2008 02:42:37 -0500 Received: from mx2.redhat.com ([66.187.237.31]:51913) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1Kz4wO-0007KI-H6 for qemu-devel@nongnu.org; Sun, 09 Nov 2008 02:42:36 -0500 Date: Sun, 9 Nov 2008 09:40:37 +0200 From: Gleb Natapov Subject: Re: [Qemu-devel] [RESEND][PATCH 0/3] Fix guest time drift under heavy load. Message-ID: <20081109074037.GA32281@redhat.com> References: <20081029152236.14831.15193.stgit@dhcp-1-237.local> <20081106081206.GD3820@redhat.com> <4912FAE5.9010100@codemonkey.ws> <200811061424.43689.paul@codesourcery.com> <491301C9.40506@codemonkey.ws> <20081106145142.GA29861@redhat.com> <49130F54.4060907@codemonkey.ws> <20081108083620.GB19381@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081108083620.GB19381@redhat.com> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Paul Brook , qemu-devel@nongnu.org On Sat, Nov 08, 2008 at 10:36:20AM +0200, Gleb Natapov wrote: > > I think the best ones are going to be intense host workload (and let's > > see how much is needed before we start drifting badly) and high guest > > frequencies with hosts that lack high resolution timers. I think with a > > high resolution guest and no host overcommit, it should be very > > difficult to produce drift regardless of what the guest is doing. > > > Later I'll try to generate load on a host an see how this affects > guest's time drift. > Just did that. Run qemu process bound to CPU 1 (taskset 1 qemu ...). Run busy loop on the same CPU (taskset 1 bash -c "while true; do x='x'; done") Run disk test utility as before inside a guest. After 40 minutes time drift is almost 1 minute, but the drift was not gradual i.e I observed gradual drift of 1 second per ~6 minutest, but sometimes there were jumps of ~10 seconds. -- Gleb.