On 4/21/26 4:32 AM, Thomas Gleixner wrote:
On Mon, Apr 20 2026 at 23:03, Waiman Long wrote:
To provide nohz_full tick support, there is a set of tick dependency
masks that need to be evaluated on every IRQ and context switch.
s/IRQ/interrupt/
This is a changelog and not a SMS service.
Switching on nohz_full tick support at runtime will be problematic
as some of the tick dependency masks may not be properly set causing
problem down the road.
That's useless blurb with zero content.
Allow nohz_full boot option to be specified without any
parameter to force enable nohz_full tick support without any
CPU in the tick_nohz_full_mask yet. The context_tracking_key and
tick_nohz_full_running flag will be enabled in this case to make
tick_nohz_full_enabled() return true.
I kinda can crystal-ball what you are trying to say here, but that does
not make it qualified as a proper change log.
There is still a small performance overhead by force enable nohz_full
this way. So it should only be used if there is a chance that some
CPUs may become isolated later via the cpuset isolated partition
functionality and better CPU isolation closed to nohz_full is desired.
Why has this key to be enabled on boot if there are no CPUs in the
isolated mask?
If you want to manage this dynamically at runtime then enable the key
once CPUs are isolated. Yes, it's more work, but that avoids the "should
only be used" nonsense and makes this more robust down the road.
OK, I will try to make it fully dynamic. Of course, it will be more work.
Cheers,
Longman
Thanks,
tglx
