Re: Zephyr as UOS slows down when SOS is busy

Geoffroy Van Cutsem

Hi Alfonso,


My best guess as to what’s happening is that there is some contention between the Service VM and the Zephyr VM to use the cache, Zephyr would typically stay in cache but now that there is some heavy load in the Service VM, it may get evicted at times. This is where Cache Allocation Technology (CAT) can help further isolate the VMs, especially against so-called “noisy neighbours. Unfortunately, Kaby Lake does not support CAT. Here is more about CAT and how to use it with ACRN:




From: acrn-users@... <acrn-users@...> On Behalf Of Alfonso Sanchez-Beato
Sent: Tuesday, January 21, 2020 1:09 PM
To: acrn-users@...
Subject: Re: [acrn-users] Zephyr as UOS slows down when SOS is busy




On Tue, Jan 21, 2020 at 1:07 PM Alfonso Sanchez-Beato <alfonso.sanchez-beato@...> wrote:



I have been playing with using Zephyr as UOS on top of Ubuntu as SOS, using the Industry scenario and launching the UOS with


I created this small program to prove that Zephyr was not affected by what happened in the SOS: (with config The program simply calculates the number of primes below a number and prints the time spent.


Although the problem runs and I get output from the serial port, I found two problems:


1. gettimeofday is not returning good times, the elapsed time is ~20 times more than the real one. I see the same problem when using k_uptime_get and k_uptime_delta. It looks related to handling of the HW clock, but the pre-defined frequency (100) seems correct.


2. More importantly, I see that the time spent in the calculation varies when I do something CPU intensive on the SOS. For instance, if I run the same calculation on the SOS, I see that Zephyr is expending 5% more time in the calculation, which should not happen and defeats the purpose of this set-up.


ACRN version is:

HV version 1.4-unstable-2020-01-09 09:45:06-bcefd673 DBG (daily tag: acrn-2019w47.1-140000p) build by ubuntu
API version 1.0


Any ideas on what might be going on?


I forgot to mention that I am testing on a NUC7i7DNH.






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