From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olivier Hanesse Subject: Re: Xen 4 TSC problems Date: Wed, 23 Feb 2011 20:04:25 +0100 Message-ID: <4D655A39.2040501@gmail.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable 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 Cc: Dan Magenheimer , xen-devel@lists.xensource.com, Xen Users , Jeremy Fitzhardinge , Mark Adams List-Id: xen-devel@lists.xenproject.org I am sorry for the lack of information. Every domUs on the dom0 are affected by this bug at the exact same time. And I had this bug on a dozen servers (all running on the same hw) since=20 October (when I switched from Xen 3.2 to 4.0). Regards Olivier Le 23/02/2011 18:19, Keir Fraser a =E9crit : > On 23/02/2011 16:16, "Dan Magenheimer" wro= te: > >> It=B9s very unlikely this is a problem with TSC. It is most likely a X= en (or >> possibly a PV Linux) problem where a guest (or dom0) either =B3goes ou= t to >> lunch=B2 for a long period, or some other timer gets stuck. The =B3cl= ocksource >> tsc unstable=B2 message is a side effect of this... it=B9s very likely= the TSC >> that IS stable and correct and the other clocksource (pvclock) has los= t/gained >> 50 minutes! >> >> Mark Adams cc=B9ed and his original xen-devel posting below. The fact= that two >> different users (possibly on the same processor/system type?) have sub= mitted >> the message with a delta so similar would lead me to believe there is = some >> timer that is =B3wrapping=B2. And since pvclock is usually the clocks= ource for >> dom0, and pvclock is driven! by Xen=B9s =B3system time=B2, a reasonab= le guess is >> that the timer that is wrapping is in Xen itself. >> >> Mark=B9s delta =3D -2999660303788 ns >> Your delta =3D -2999660334211 ns >> >> Googling, I see the HPET wraparound is ~306 seconds and this delta is = about >> 3000 seconds, so that may be a bad guess. >> >> Keir, any thoughts on this? Do you recall any post-4.0 patches that m= ay have >> fixed this? > I've never seen a 3000s wrap, and I don't know of anything that would h= ave > fixed a bug like this. If this is a Xen time wrap of some kind then it = would > affect all running guests; it's not clear here whether only one, or all= , > guests see the wrap. > > K. > >> Thanks, >> Dan >> >> References: >> http://lists.xensource.com/archives/html/xen-devel/2010-10/msg00210.ht= ml >> https://lkml.org/lkml/2010/10/26/126 >> >> >> From: Olivier Hanesse [mailto:olivier.hanesse@gmail.com] >> Sent: Wednesday, February 23, 2011 3:50 AM >> To: xen-devel@lists.xensource.co! m; Xen Users >> Subject: [Xen-devel] Xen 4 TSC problems >> >> >> Hello >> >> >> >> I've got an issue about time keeping with Xen 4.0 (Debian squeeze rele= ase). >> >> >> >> My problem is here (hopefully I amn't the only one, so there might be = a bug >> somewhere) : http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=3D599161= #50 >> >> After some times, I got this error : Clocksource tsc unstable (delta = =3D >> -2999660334211 ns). It has happened on several servers. >> >> >> >> Looking at the output of "xm debug-key s;" >> >> >> >> (XEN) TSC has constant rate, deep Cstates possible, so not reliable, w= arp=3D2850 >> (count=3D3) >> >> >> >> I am using a "Intel(R) Xeon(R) CPU L5420 @ 2.50GHz", which has the >> "constant_tsc", but not the "nonstop_tsc" one. >> >> On other systems with a newer cpu with "nonstop_tsc", I don't have thi= s issue >> (systems are running the same distros with same config). >> >> >> >> I tried to boot with "max_cstate=3D0", but nothing changed, my TSC isn= 't >> reliable and after some times, I will got the "50min" issue again. >> >> >> >> I don't unders! tand how a system can do a jump of "50min" in the fut= ure. Why >> 50min ? it is not 40min, not 1 hour, it is always 50min. >> >> I don't know how to make my TSC "reliable" (I already disable everythi= ng about >> Powerstate in BIOS Settings). >> >> >> >> Any ideas ? >> >> >> >> Regards >> >> >> >> Olivier >> >