Re: [RFC PATCH 0/2] tick/nohz: Add runtime control of non-idle tick suppression

[Waiman Long <longman@redhat.com>]

On 10/15/26 8:43 AM, Peng Wang wrote:
> Workloads and their need for periodic ticks can change after boot.
> This series lets userspace choose at runtime which CPUs in the boot-time
> nohz_full set retain the non-idle scheduler tick and which are permitted
> to stop it, while preserving the existing isolation configuration.
>
> The first patch adds a per-CPU tick dependency; the second exposes a
> sysfs CPU list. Permission defaults to all nohz_full CPUs. Revocation
> uses the existing asynchronous kick. Idle tick suppression is unchanged,
> and policy persists across hotplug.
So you are basically setting up more nohz_full CPUs than the system 
actually needs to use at the moment and so want to disable nohz/tick 
part of nohz_full CPUs that don't need it. Can you elaborate more about 
the problems solve by introducing this new behavior?
>
> Existing cpuset partition modes do not express this independent tick
> policy. Feedback on the proposed interface is welcome.

We are planning to eventually extend cpuset partition mode to change 
nohz_full at runtime. This is still a work in progress.

Regards,
Longman

>
> Thanks,
> Peng
>
> Peng Wang (2):
>    tick/nohz: Add a policy dependency for full dynticks
>    cpu: Add sysfs control of full dynticks policy
>
>   .../ABI/testing/sysfs-devices-system-cpu      | 40 ++++++++++++
>   drivers/base/cpu.c                            | 46 ++++++++++++++
>   include/linux/tick.h                          |  8 ++-
>   include/trace/events/timer.h                  |  3 +-
>   kernel/time/tick-sched.c                      | 62 +++++++++++++++++++
>   5 files changed, 156 insertions(+), 3 deletions(-)
>
>
> base-commit: 0fcb05b72344f40806cbe810de8872f1698bf053