Re: [PATCH v4 00/11] Dynamic Housekeeping Management (DHM) via CPUSets

[Frederic Weisbecker <frederic@kernel.org>]

Le Fri, Jul 10, 2026 at 11:28:11AM +0800, Jing Wu a écrit :
> This series introduces Dynamic Housekeeping Management (DHM) to the Linux
> kernel, enabling runtime reconfiguration of kernel-noise housekeeping
> (nohz_full tick suppression, RCU NOCB offloading, and managed IRQ
> migration) through the existing cgroup v2 cpuset isolated partition
> mechanism — no new kernel ABI required.
> 
> When a cpuset partition is set to isolated mode, DHM cycles each CPU in
> that partition offline, reconfigures the housekeeping masks (removing the
> CPU from HK_TYPE_KERNEL_NOISE and related types), and brings it back
> online.  The subsystems (tick/nohz, RCU NOCB, genirq) pick up the new
> masks through their existing CPU hotplug callbacks.  Destroying the
> partition reverses the cycle: each CPU is taken offline, restored to all
> housekeeping masks, and brought back online.
> 
> Housekeeping cpumask pointers are RCU-protected to allow lock-free readers
> during updates.  A global dhm_cycling_cpus mask suppresses transient
> cpuset partition invalidation while CPUs are being cycled.
> 
> This work is related to Waiman Long's [PATCH-next 00/23] series
> (20260421030351.281436-1-longman@redhat.com), which also targets runtime
> cpuset housekeeping control.  DHM's distinguishing feature is zero-boot-
> parameter activation: nohz_full+nocb isolation can be achieved at runtime
> without any boot-time nohz_full= or rcu_nocbs= parameters.
> 
> Signed-off-by: Jing Wu <realwujing@gmail.com>
> Signed-off-by: Qiliang Yuan <yuanql9@chinatelecom.cn>

Sorry for the delay, I'm finally on it.

One thing I would like to have is to make HK_TYPE_KERNEL_NOISE to always
be a superset of HK_TYPE_DOMAIN. Ie: Cpuset's nohz_full should imply
isolated domain partition. Or to put it another way: a nohz_full CPU should
always run on isolated domains. If I could do it again, I would enforce
the boot nohz_full= to always be a subset of isolcpus=domain. But we
didn't know the possible usecase of it at the time.

Thanks.

-- 
Frederic Weisbecker
SUSE Labs