core performance

[Stephen Hemminger]

On Mon, 30 Sep 2024 08:57:26 -0700
Stephen Hemminger <stephen at networkplumber.org> wrote:

> > After placing counters all over the code, we realize that some threads are uniformly slow, in other words there is no application level issue that is throttling one thread over the other. We come to the conculsion that either the Cores on which they are running are not at the same frequency which seems doubtful or the threads are not getting a chance to execute on the cores uniformly.
> > 
> > It seems that isolcpus has been deprecated in recent versions of linux.
> > 
> > What is the recommended approach to prevent the kernel from utilizing some CPU threads, for anything other than the threads that are launched on them.  
> 
> On modern Linux systems, CPU isolation can be achieved with cgroups.

Did you checkout the links in the section in the docs on core isolation.
   https://doc.dpdk.org/guides/linux_gsg/enable_func.html

   https://www.suse.com/c/cpu-isolation-practical-example-part-5/
   https://www.rcannings.com/systemd-core-isolation/

There is also a much more complex and detailed script which is part of
the open source project DanOs here:

   https://github.com/danos/vyatta-cpu-shield/blob/master/usr/bin/cpu_shield

If you really want isolated CPU's you have to some more complex stuff to make
sure interrupts etc don't run on that CPU. Also never use CPU 0