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Re: [Xen-devel] Xen optimization

> On Wed, Oct 24, 2018 at 2:24 AM Stefano Stabellini 
> <stefano.stabellini@xxxxxxxxxx> wrote:
> It is good that there are no physical interrupts interrupting the cpu.
> serrors=panic makes the context switch faster. I guess there are not
> enough context switches to make a measurable difference.

Yes, when I did:
grep ctxt /proc/2153/status
I got:
voluntary_ctxt_switches:        5
nonvoluntary_ctxt_switches:     3

> I don't have any other things to suggest right now. You should be able
> to measure an overall 2.5us IRQ latency (if the interrupt rate is not
> too high).

This bare-metal application is the most suspicious, indeed. Still
waiting answer on Xilinx forum.

>  Just to be paranoid, we might also want to check the following, again it
> shouldn't get printed:
> diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
> index 5a4f082..6cf6814 100644
> --- a/xen/arch/arm/vgic.c
> +++ b/xen/arch/arm/vgic.c
> @@ -532,6 +532,8 @@ void vgic_inject_irq(struct domain *d, struct vcpu *v, 
> unsigned int virq,
>      struct pending_irq *iter, *n;
>      unsigned long flags;
> +    if ( d->domain_id != 0 && virq != 68 )
> +        printk("DEBUG virq=%d local=%d\n",virq,v == current);
>      /*
>       * For edge triggered interrupts we always ignore a "falling edge".
>       * For level triggered interrupts we shouldn't, but do anyways.
Checked it again, no prints. I hoped that I will discover some vIRQs
or pIRQs slowing things down but no, no prints.
I might try something else instead of this bare-metal application
because this Xilinx SDK example is very suspicious.

Thank you for your time.


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