From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: System time monotonicity Date: Tue, 27 Mar 2007 11:47:40 +0100 Message-ID: References: <20070326200447.GA3730@totally.trollied.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20070326200447.GA3730@totally.trollied.org.uk> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: John Levon Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On 26/3/07 21:04, "John Levon" wrote: >> Small backwards time deltas are possible from the current time code. You'll >> have to filter them out yourself if you can't deal with them. We could add >> extra code in Xen to stop this happening for any individual VCPU > > Some instrumentation indicated that we had cross-VCPU jitter of > significant deltas, ~18us at worst. Though the instrumentation wasn't > completely reliable so that might not be accurate. I should add that time synchronisation is currently broken in xen-unstable, and has been for about two weeks. I just checked in a patch (based on one from Jan Beulich) to fix this (changeset 14573:ba9d3fd4ee4b). -- Keir