Re: [ARM] Native application design and discussion (I hope)

[Julien Grall <julien.grall@arm.com>]

On 27/04/17 18:26, Volodymyr Babchuk wrote:
> Hi Julien,

Hi Volodymyr,

> I'm back with profiler results.
>
>>> Oh, yes. Sorry I forgot this thread. Continuing on that, you said that "Now
>>> profiler shows that hypervisor spends time in spinlocks and p2m code."
>>>
>>> Could you expand here? How the EL0 app will spend time in p2m code?
>> I don't quite remember. It was somewhere around p2m save/restore
>> context functions.
>> I'll try to restore that setup and will provide more details.
> So, there are top 5 functions:
>
> p2m_restore_state - 10.6%

This is with your el0_app branch? Or did you make some changes?

For instance, the p2m_restore_state has been reworked for Xen 4.9 and 
some of the isb() could be dropped.

> spin_lock - 8.4%
> spin_unlock_irqrestore - 6%

I am a bit confused on what you are profiling. Are you only profiling 
context save/restore? Or do you also profile the rest of the hypervisor?

E.g, how many time spin_*lock are called... That would help to know if 
the problem is because of the number of locks taken or potential 
optimization that we didn't implement.

> ctxt_switch_to_partial - 5.7%
> gicv2_hcr_status - 4.6%

Cheers,

>
> per-source-file statistics:
>
> spinlock.c - 22%
> entry.S - 15%
> arm/domain.c - 11.6%
>

-- 
Julien Grall

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