Re: A question regarding isolated cpus and software interrupts

[David Aldrich via lttng-dev <lttng-dev@lists.lttng.org>]

Hi Mathieu

Thanks for your reply.

> How are the cores isolated on your system (exact kernel command line
> options or commands issued) ? There are various degree of fine-tuning
> to prevent disturbance from the tick (nohz full), scheduling, and
> irqs that can be done explicitly. So depending on your specific
> configuration, you may be missing isolation options that would
> prevent the softirq from running on your isolated cpus.

Our kernel parameters are:

ro skew_tick=1 rcu_nocb_poll rcu_nocbs=4-31 nohz=on nohz_full=4-31
kthread_cpus=0-3 irqaffinity=0-3 isolcpus=managed_irq,domain,4-31
intel_pstate=passive nosoftlockup tsc=nowatchdog intel_iommu=on
iommu=pt default_hugepagesz=1G hugepagesz=1G hugepages=4
vfio_pci.enable_sriov=1 vfio_pci.disable_idle_d3=1

(the affected thread runs on core 4).

Best regards
David