From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Dan Magenheimer" Subject: RE: [PATCH] record max stime skew (was RE: [PATCH] strictly increasing hvm guest time) Date: Thu, 3 Jul 2008 10:24:13 -0600 Message-ID: <20080703102413734.00000003744@djm-pc> References: Reply-To: "dan.magenheimer@oracle.com" Mime-Version: 1.0 Content-Type: multipart/mixed; boundary=-------8462841084628410 Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser , "Xen-Devel (E-mail)" Cc: Dave Winchell List-Id: xen-devel@lists.xenproject.org This is a multi-part message in MIME format ---------8462841084628410 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable > > Attached is the patch. Interestingly, on my single-socket > > two-core recent-vintage Intel processor, this patch reports > > a max skew of >13 usec, much higher than the values I'm > > seeing from "xm debug-key t". I wonder if this is due to > > a mistake in my patch (though I don't see it) or if the > > various stime error corrections are not converging as > > expected, resulting in a broader stime skew between > > processors than expected? > = > Perhaps this relatively large skew happens at start of day, before the > periodic calibration has 'locked on'? Indeed you are correct. This updated patch now reports zero skew as expected. IMHO, it would be nice to put this patch into the tree as it will be good for helping to diagnose time skew problems such as the one just reported on the list. 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