Le Mon, Mar 30, 2026 at 07:43:21PM +0800, Qiliang Yuan a écrit : 11;rgb:2e2e/3434/3636> Hi Peter, > > On Wed, Mar 25, 2026 at 02:57:07PM +0100, Peter Zijlstra wrote: > > I think I asked this a while ago; why do we have more than one mask? > > What is the actual purpose of being able to separate RCU from Timers? > > That's a fair point. For the vast majority of use cases (like NOHZ_FULL), > these masks are indeed identical and should be updated as a single unit. > > The original motivation for separation was to allow extreme fine-tuning in > HFT environments—for example, offloading RCU callbacks to keep a core > mostly clean but allowing pinned timers for specific localized > telemetry/monitoring. > > However, I acknowledge this adds significant complexity. In V13, I will > unify these into a single "Global Housekeeping Mask" by default to > simplify the configuration space, while keeping the underlying notifier > infrastructure flexible enough for future specialized needs.
More precisely we only need four flags: HK_TYPE_DOMAIN_BOOT (isolcpus=) HK_TYPE_DOMAIN (cgroup v2 isolated partition + isolcpus=) HK_TYPE_KERNEL_NOISE (nohz_full=) HK_TYPE_MANAGED_IRQ (isolcpus=managed_irq) All the aliases of HK_TYPE_KERNEL_NOISE need to be renamed to HK_TYPE_KERNEL_NOISE. Thanks. -- Frederic Weisbecker SUSE Labs
