Large interruptions for EAL thread running on isol core

[Antonio Di Bacco]

Thank you, didn't know that "System management units" could steal
CPU!!! That is scary

On Thu, Jun 23, 2022 at 8:42 PM Stephen Hemminger
<stephen at networkplumber.org> wrote:
>
> On Thu, 23 Jun 2022 20:03:02 +0200
> Antonio Di Bacco <a.dibacco.ks at gmail.com> wrote:
>
> > I'm running a DPDK thread on an isolated core. I also set some  flags
> > that could help keeping the core at rest on linux like: nosoftlockup
> > nohz_full rcu_nocbs irqaffinity.
> >
> > Unfortunately the thread gets some interruptions that stop the thread
> > for about 20-30 micro seconds. This seems smal but my application
> > suffers a lot.
> >
> > I also tried to use  rte_thread_set_priority that indeed has a strong
> > effect but unfortunately creates problems to Linux (like network not
> > working).
> >
> > Is there any other knob that could help running the DPDK thread with
> > minimum or no interruptions at all?
>
> Look with perf and see what is happening.
> First check for interrupt affinity.
> Don't try real time priority.
>
> The other thing to look for would be any BIOS settings.
> Some system management units can take away CPU silently for polling
> some internal housekeeping.