On Fri, Mar 17, 2023 at 03:33:13PM -0300, Marcelo Tosatti wrote: > On Fri, Mar 17, 2023 at 02:44:47PM +0100, Michal Hocko wrote: > > From: Frederic Weisbecker <frederic@xxxxxxxxxx> > > > > Provide this new API to check if a CPU has been isolated either through > > isolcpus= or nohz_full= kernel parameter. > > > > It aims at avoiding kernel load deemed to be safely spared on CPUs > > running sensitive workload that can't bear any disturbance, such as > > pcp cache draining. > > Hi Michal, > > This makes no sense to me. > > HK_TYPE_DOMAIN is set when isolcpus=domain is configured. > HK_TYPE_TICK is set when nohz_full= is configured. > > The use-cases i am aware of use either: > > isolcpus=managed_irq,... nohz_full= > OR > isolcpus=domain,managed_irq,... nohz_full= > > So what is the point of this function again? > > Perhaps it made sense along with, but now does not make sense > anymore: > > Subject: [PATCH 1/2] sched/isolation: Merge individual nohz_full features into a common housekeeping flag > > The individual isolation features turned on by nohz_full were initially > split in order for each of them to be tunable through cpusets. However > plans have changed in favour of an interface (be it cpusets or sysctl) > grouping all these features to be turned on/off altogether. Then should > the need ever arise, the interface can still be expanded to handle the > individual isolation features. > > But Michal can just use housekeeping_test_cpu(cpu, HK_TYPE_TICK) and > the convertion of nohz_full features into a common housekeeping flag > can convert that to something else later? Actually introducing cpu_is_isolated() seems fine, but it can call housekeeping_test_cpu(cpu, HK_TYPE_TICK) AFAICS.
