A question regarding isolated cpus and software interrupts
David Aldrich
david.aldrich.ntml at gmail.com
Fri May 30 11:00:23 EDT 2025
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
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