Re: [Xen-ia64-devel] [IPF-ia64] with Cset 10690, creating aVTImakexen0 hang

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

Hi SAKAI.

The Anthony's modification is required.
Without the modification, all physical CPUs end up in the idle loop and
can't get out of it in spite of runnable vcpus existance because
of TIMER_SLOP. This issue isn't related to VT-i domain.

Thanks.

On Wed, Jul 12, 2006 at 10:30:47PM +0800, Xu, Anthony wrote:
> Hi, SAKAI
> Forget wrong analysis in early email,
> 
> In the phase of EFI boot, there are many IO operations, so dom0 is woken up by
> VTIdomain in most time, while hlt_timer is still registered, this may cause 
> more
> timer interrupts injected to dom0 than before.
> 
> Hope following modification help
> #define TIMER_SLOP (50*1000) /* ns */
>       set_timer(&v->arch.hlt_timer, vcpu_get_next_timer_ns(v)+TIMER_SLOP );
>       do_sched_op_compat(SCHEDOP_block, 0);
>       stop_timer(&v->arch.hlt_timer);
> 
> Thanks,
> Anthony
> 
> 
> >-----Original Message-----
> >From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
> >[mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Xu, Anthony
> >Sent: 2006?7?12? 21:13
> >To: Atsushi SAKAI; Alex Williamson; Zhang, Xiantao
> >Cc: Isaku Yamahata; xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >Subject: RE: [Xen-ia64-devel] [IPF-ia64] with Cset 10690,creating 
> >aVTImakexen0
> >hang
> >
> >>From: Atsushi SAKAI
> >>Sent: 2006?7?12? 19:05
> >>My primary motivation is correct display of xenmon.py and xentop in 
> >>BVT/CREDIT.
> >>(N.B. SEDF displayed as same as x86, but BVT/CREDIT are not)
> >>If only domU emulation is applied, it is a half way from my motivation.
> >>Is dom0 dispatch another home work?
> >>
> >
> >I suspect the slowness is not due to dom0 being scheduled out, but due to
> >hlt_timer
> >didn't work as expected.
> >           set_timer(&v->arch.hlt_timer, vcpu_get_next_timer_ns(v));
> >           do_sched_op_compat(SCHEDOP_block, 0);
> >There is a time window between set_timer and dom0 being scheduled out, and 
> >psr.i
> >is 1. So if hlt_timer fires before do_sched_op_compat being called, dom0 will
> >not be woken up by hlt_timer, and there is no timer interrupt for dom0 until
> >domo
> >is woken up ,yes, dom0 can be woken up by other external interrupts, but not
> >by
> >timer interrupt. And since dom0 is involved in VTIdomain bootup, this may 
> >lead
> >to slowness of VTIdomain bootup.
> >
> >Above is my analysis, there isn't any evidence.
> >
> >You can do experiment to check it.
> >Change above code sequence as following, this may reduce the impact of time
> >window.
> >
> >set_timer(&v->arch.hlt_timer,
> >cycle_to_ns(local_cpu_data->itm_delta)+NOW());
> >do_sched_op_compat(SCHEDOP_block, 0);
> >
> >_______________________________________________
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> >Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >http://lists.xensource.com/xen-ia64-devel
> 
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-- 
yamahata

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