Re: [PATCH v2 1/2] cpuidle: governors: menu: Refine stopped tick handling

[Ionut Nechita (Wind River)]

On Mon, 23 Feb 2026 16:38:55 +0100, Rafael J. Wysocki wrote:
> Update the menu governor in accordance with the above and use twice
> the tick period length as the "safe timer range" for allowing the
> original predicted_ns value to be used even if the tick has been
> stopped.

Tested this on 6.12.79-rt17 with isolated CPUs (nohz_full=1-16,
isolcpus=nohz,domain,managed_irq,1-16) on Intel Xeon Gold 6338N.

cyclictest --priority 95 --nsecs --duration 600 --affinity 1-15
           --threads 15 --mainaffinity 0

Before (6.12.79-rt17 without patch):
  Avg: ~1780ns, Max T:3-T:8: 9300-9700ns

After (6.12.79-rt17 + this patch):
  Avg: ~1790ns, Max T:3-T:14: 5200-6100ns

The patch reduces worst-case latency on threads T:3-T:14 from
~9500ns to ~5800ns on isolated CPUs with nohz_full. T:0-T:2 still
show occasional higher spikes (9400-10700ns) but the overall tail
latency improvement is clear.

Tested-by: Ionut Nechita <sunlightlinux@xxxxxxxxx>