[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Re: Fix for get_s_time()
Keir, Last nights run had the error in the 12 ppm range. Here is the change we have been talking about. -Dave Dave Winchell wrote: Keir Fraser wrote:On 24/4/08 17:04, "Dave Winchell" <dwinchell@xxxxxxxxxxxxxxx> wrote:yes, this is the issue. What you suggest should be fine and I am trying it now. With the locking version (and a fix to a bug I introduced) I got .0012% erroron an overnight run with hpet layered on get_s_time_mono(), which is themax(prev, cur) layer on get_s_time we discussed.12 parts per million is pretty good. Is that cumulative deviation from 'walltime' over ~12 hours?yes, deviation between the guest's time and an ntp reference.That's true. And, as we have discussed, this error seems to vary quite a bit platform to platform for some reason. I will verify that this still is the case.That could easily be explained by the fact that Xen system time is not sync'ed with ntp.-Dave-- Keir diff -r 483d006cc607 xen/arch/x86/time.c --- a/xen/arch/x86/time.c Fri Apr 25 13:46:27 2008 +0100 +++ b/xen/arch/x86/time.c Fri Apr 25 15:40:31 2008 -0400 @@ -836,9 +836,9 @@ static void local_time_calibration(void /* Disable IRQs to get 'instantaneous' current timestamps. */ local_irq_disable(); + curr_master_stime = read_platform_stime(); + curr_local_stime = get_s_time(); rdtscll(curr_tsc); - curr_local_stime = get_s_time(); - curr_master_stime = read_platform_stime(); local_irq_enable(); #if 0 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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