Re: [PATCH 4/5] rteval: hackbench.py: Enable running on a system with low memory

[Punit Agrawal <punitagrawal@gmail.com>]

Hi John,

John Kacur <jkacur@redhat.com> writes:

> On Wed, 1 Sep 2021, Punit Agrawal wrote:
>
>> From: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
>> 
>> The hackbench workload refues to run on RockPro64, a hexacore 64bit
>> Arm board with 4GB memory, complaining about insufficient memory
>> per-core.
>> 
>> On further investigation, it turns out that workload is using an
>> arbitrary limit of 0.75 GB/core but will quite happily run on much
>> lower lower memory systems.
>> 
>> Instead of preventing execution, convert the info message to a warning
>> when the memory is lower than expected but continue execution. This
>> should enable the workload to be used on a wider range of systems.
>> 
>> Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
>> ---
>>  rteval/modules/loads/hackbench.py | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>> 
>> diff --git a/rteval/modules/loads/hackbench.py b/rteval/modules/loads/hackbench.py
>> index 3b692070e9d9..ab028c495d8b 100644
>> --- a/rteval/modules/loads/hackbench.py
>> +++ b/rteval/modules/loads/hackbench.py
>> @@ -55,9 +55,8 @@ class Hackbench(CommandLineLoad):
>>          if ratio >= 0.75:
>>              mult = float(self._cfg.setdefault('jobspercore', 2))
>>          else:
>> -            self._log(Log.INFO, "Low memory system (%f GB/core)! Not running" % ratio)
>> +            self._log(Log.WARN, "Low memory system (%f GB/core)!" % ratio)
>>              mult = 0
>> -            self._donotrun = True
>>  
>>          sysTop = SysTopology()
>>          # get the number of nodes
>> -- 
>> 2.32.0
>> 
>> 
>
> I'm not sure that I can accept this. The number isn't entirely arbitrary, 
> it's based on verifying machines as realtime capable for customers, in 
> which case I'd rather it fails early.

I think there's a misunderstanding. The above check only prevents the
hackbench workload from running - which takes ~2-3MB in the default
configuration on the board I tested. rteval (along with cyclictest,
kcompile and other workloads) executes without any issues.

In terms of memory requirements for real time systems, I am not sure
there is a single number that is valid across all applications or
systems. Any such requirement only manages to alienate certain class of
rteval users. I thought a warning was a good compromise.

I am hoping you will reconsider the need to introduce a user option for
this case.

> Maybe there is some other way to indicate that the user is okay with
> lower memory system, such as passing an --embedded flag or something
> of that nature?

If the above doesn't convince you, I will look to adding an option. How
about calling the option "--low-memory-system" to clearly state what it
enables. "Embedded" is not well-defined and hard to guess what it
relates to.