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Re: [Xen-devel] xen/arm: Domain not fully destroyed when using credit2





On 24/01/17 14:16, Dario Faggioli wrote:
On Tue, 2017-01-24 at 13:49 +0000, Julien Grall wrote:
On 24/01/17 13:40, Dario Faggioli wrote:
Ah, wow... And how --forgive my naiveness-- do you measure / check
that?

I added a print in the interrupt path (gic_interrupt for ARM) to
dump
the interrupt number. This needs to be restrict to CPU2 and above to
avoid been flooded:

if ( smp_processor_id() > 1 )
   printk("%s: CPU%u IRQ%u\n", __FUNCTION__, smp_processor_id(),
irq);

Ok.

I also added a print in the idle loop before and after the idling
instruction (wfi for ARM, pm_idle for x86 I think). You can see the
CPU
to go in idle mode but never coming back.

I see. Yes, this is very different on x86.

There, we have tracing (BTW, did that made it to ARM eventually?) and
there's TRC_PM_IDLE_ENTRY/EXIT which do pretty much the same of your
printk-s.

There is patch on the ML for xentrace support (see [1]) but nothing has been upstreamed yet. Waiting for a new version from the contributor.


And if I look at it, I do see even totally idle (from the scheduler
point of view) pCPUs, I indeed see them going back and forth from and
to C3.

My knowledge on x86 is limited. When does a CPU decides to leave the idle mode?

In the case of ARM, the wfi instruction will put the CPU in idle mode until an interrupt is received.

Cheers,

[1] https://lists.xenproject.org/archives/html/xen-devel/2016-04/msg00464.html

--
Julien Grall

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