From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Winchell Subject: Re: [PATCH] Deferrable Timer Date: Fri, 18 Jul 2008 11:44:35 -0400 Message-ID: <4880BA63.5050909@virtualiron.com> References: <1104166E0B63A341805FDB977862AAD201BC154A@pdsmsx414.ccr.corp.intel.com> <1104166E0B63A341805FDB977862AAD201BF479B@pdsmsx414.ccr.corp.intel.com><487F53D1.6030104@virtualiron.com> <1104166E0B63A341805FDB977862AAD201BF4DE8@pdsmsx414.ccr.corp.intel.com> <1104166E0B63A341805FDB977862AAD201BF4DEF@pdsmsx414.ccr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1104166E0B63A341805FDB977862AAD201BF4DEF@pdsmsx414.ccr.corp.intel.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "Yu, Ke" Cc: "Tian, Kevin" , xen-devel@lists.xensource.com, Dave Winchell , Keir Fraser , "Wei, Gang" List-Id: xen-devel@lists.xenproject.org Yu, Ke wrote: >Yu, Ke wrote: > > >>Dave, >> >>Glad to see there is deferrable timer application. Please go ahead >>with that. And I will keep you updated if there is finding in my side. >> >>BTW, Could you please elaborate more on the >>"guest-handles-missed-tick" case? Since there is no need to inject >>missed tick to guest, which timer would be used as deferrable timer? >> >> > >Oh, I catch your points now, please ignore my previous question. You >actually means that: since guest can handle the missed tick correcty, it >is acceptable that the hpet/vpt timer is defered, so the hpet/vpt timer >itself can be deferrable timer. > Yes. > so is the >"guest-does-not-handle-missed-ticks" case, since xen can handle that by >inject missed tick respectively. > > For the guest-does-not-handle-missed-ticks case we inject the correct number of interrupts, i.e. N*period, N an integer, but we can delay a bit before doing so. So I think we can use deferrable timers for both policies. >If my understanding is correct, I would say your point is truly good, I >expect this will reduce the timer count much especially when there is >multiple HVMs. > >Best Regards >Ke > > > >>Best Regards >>Ke >> >>Dave Winchell wrote: >> >> >>>Ke, >>> >>>One would think that hpet or vpt support for the >>>guest-handles-missed-ticks policy would be a good application for a >>>deferrable timer. If a deferrable timer were used, then the >>>comparator (cmp) would have to be warped to a non-integer multiple >>>of the period. This is because Linux reads the comparator register >>>to estimate the delay since the interrupt was posted. >>>I don't think warping like this will be a problem. At some point, I >>>can test this. >>> >>>I think we could use the deferrable timer for the >>>guest-does-not-handle-missed-ticks >>>policy as well. >>> >>>Any investigation that you want to do in the platform timer area >>>would be fine. Or I can do it, but that will probably be after I do >>>the vpt.c/hpet.c integration work. >>> >>>thanks, >>>Dave >>> >>> >>> >>>>Best Regards >>>>Ke >>>> >>>>_______________________________________________ >>>>Xen-devel mailing list >>>>Xen-devel@lists.xensource.com >>>>http://lists.xensource.com/xen-devel >>>> >>>> >>_______________________________________________ >>Xen-devel mailing list >>Xen-devel@lists.xensource.com >>http://lists.xensource.com/xen-devel >> >> > > >