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

John Kacur
2021-09-13T12:52:44Z

On Mon, 13 Sep 2021, Punit Agrawal wrote:

> 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.
>

You're right, the original code only prevents hackbench from running, it
doesn't cause rteval to fail early.

Hmmn, it almost seems like the original code was a development hack that
wasn't removed. Not sure, give me a short time to think about it.

John