Benchmarking Genode TrustZone

[Stefan Kalkowski]

Hi Tiago,

On 06/28/2016 11:55 AM, Tiago Brito wrote:
> Hi, so after comparing the binaries I realized that my NW application is
> using hard float instruction, unlike it's SW counter part.
> 
> I changed my NW application toolchain for one which support soft float in
> order to check if my measurements are consistent. And in some way the
> execution time gap between both for-loops decreased significantly, but
> there's still a 100 ms gap between both execution times.
> 
> Before the NW was measuring 155 ms and the SW was measuring 610 ms. Now the
> NW is measuring 500 ms whilst the SW is measuring the same 610 ms as before.
> 
> My theory is that Genode's scheduling might be delaying the SW execution. I
> say this because I added a print in the resume function of the thread
> scheduler and it prints several times when the SW for-loop is executing.
> 
> What I want to ask is, is my theory plausible? Would the SW scheduler delay
> the execution by 100 ms? It seems a bit too much time...
> What can I do to shorten this time gap between both executions?
> 

By default, if you do not configure any CPU quota and priority, the
kernel will schedule round-robin. As long as the "normal" world is not
stopped during the calculation within your "secure" Genode component, it
will be executed side-by-side. But I wonder why it is not stopped - did
you changed the execution model?

If you want to ensure that your specific calculation routine is always
executed when it is runnable, you have to add a:

  <resource name="CPU" quantum="100"/>

in its start node within the XML configuration of the init component.
This will give 100% of the CPU quota to your component. But be aware
that you can easily starve other components this way, as long as your
component never blocks.

Regards
Stefan

> Thanks in advance, Tiago
> 
> 2016-06-27 12:16 GMT+01:00 Tiago Brito <tb.genode at ...9...>:
> 
>> Hi again, I'm using the linaro's arm-linux-gnueabihf 5.3 toolchain to
>> compile the application running on top of the NW linux, but I want to try
>> and compile it using the same compiler version used for genode since the
>> use of different compilers is probably interfering with my benchmark
>> measurements (it's the only variant).
>>
>> I tried using the GCC present in genode's toolchain but I'm having several
>> No such file or directory errors with stdio.h and string.h includes. My
>> application also uses sockets, so the necessary include files are used and
>> may cause similar errors in the compilation process.
>>
>> Do you have any suggestion on how to solve this and get the same basic
>> for-loop to show similar performance results in both the Normal and Secure
>> World execution contexts?
>>
>> Thanks, Tiago
>>
>> 2016-06-23 17:20 GMT+01:00 Christian Helmuth <
>> christian.helmuth at ...1...>:
>>
>>> Hello Tiago,
>>>
>>> On Thu, Jun 23, 2016 at 04:32:18PM +0100, Tiago Brito wrote:
>>>> I did not check if the binary code is similar, but I did measure just
>>> the
>>>> for-loop in both worlds and the times are those I described previously.
>>>
>>> You really should compare the binary code as example that's slower in
>>> SW uses floating arithmetics unless I'm mistaken. If the code is
>>> similar and the execution time differs much, there may be an issue
>>> with FPU handling in SW.
>>>
>>> Greets
>>> --
>>> Christian Helmuth
>>> Genode Labs
>>>
>>> http://www.genode-labs.com/ · http://genode.org/
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>>
>>
> 
> 
> 
> ------------------------------------------------------------------------------
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-- 
Stefan Kalkowski
Genode Labs

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