xenomai: tune kernel config for low latency

[leograba]

In the Xenomai docs and also on Intel ECI docs, there are comments on kernel config that help with low latency, which improves the real-time reliability and performance.

From https://v4.xenomai.org/dovetail/rulesofthumb/:

• CONFIG_DEBUG_IRQ_PIPELINE and CONFIG_DEBUG_DOVETAIL are helpful to keep the development process sane.
• CONFIG_RAW_PRINTK is useful and recommended for debugging Xenomai out-of-band issues.

From https://v4.xenomai.org/core/user-api/scheduling/:

• CONFIG_EVL_SCHED_QUOTA and CONFIG_EVL_SCHED_TP enabled to give users more scheduler options for the Xenomai out-of-band scheduler.

From https://eci.intel.com/docs/3.1/appendix.html#eci-kernel-configuration-optimizations:

• CONFIG_NO_HZ and CPU_FREQ_STAT disabled to reduce task scheduling clock overhead.
• CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE enabled as default to prevent the CPU governor from throttling the CPU frequency for power-saving.
• CONFIG_SUSPEND and CONFIG_PM disabled to prevent power management features to introduce spikes to latency.
• CONFIG_VIRT_CPU_ACCOUNTING and CONFIG_VIRT_CPU_ACCOUNTING_GEN for more accurate task and CPU time accounting.
• CONFIG_RCU_NOCB_CPU for CPU temporal isolation.

Each config in this commit was enabled individually and tested for 5 minutes under stress, using the Scary Grinder workload as defined on the doc https://v4.xenomai.org/core/benchmarks/#stress-workloads

A final stress test was run for 3 hours. This is the same idea as the "EVL stress" test defined on https://v4.xenomai.org/ports/, except it was not run for 24h.

[microhobby]