From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Levon Subject: Re: [PATCH] TSC scaling for live migration between platforms with different TSC frequecies Date: Thu, 18 Jun 2009 12:45:35 -0400 Message-ID: <20090618164535.GA30082@movementarian.org> References: <4FA716B1526C7C4DB0375C6DADBC4EA3417372D32E@LONPMAILBOX01.citrite.net> <8ef68a49-a145-4de2-898c-ab5e27937028@default> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <8ef68a49-a145-4de2-898c-ab5e27937028@default> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Dan Magenheimer Cc: Ian Pratt , xen-devel@lists.xensource.com, Keir Fraser , "Zhang, Xiantao" List-Id: xen-devel@lists.xenproject.org On Thu, Jun 18, 2009 at 08:58:49AM -0700, Dan Magenheimer wrote: > Other apps (and/or the OS kernel) may use TSC to > approximate the passage of time, and for these apps > (and gettimeofday in the Linux kernel), this TSC scaling > patch is a must. Unfortunately, both kinds of apps could > be running simultaneously on the same guest. And > in either case, RDTSC frequency may be quite high. Certainly Solaris relies on the TSC for time-keeping, and uses it very heavily. To the extent that I doubt it's even feasible to migrate to a machine where scaling needs to be done, and such a migration should be refused, since it would essentially kill the guest. > question is: If it is important to ALWAYS emulate RDTSC, > can the Xen code be written to handle RDTSC emulation > much faster? If it could be made fast enough, the I'd be amazed if this were possible. regards john