Re: [RFC PATCH v2 1/2] tick/nohz: Add a policy dependency for full dynticks

[Frederic Weisbecker <frederic@kernel.org>]

Le Fri, Oct 30, 2026 at 12:02:53AM +0800, Peng Wang a écrit :
> > Ok in that case, do you know about the current work in progress
> > to make nohz_full opt-able through cpusets? It implies taking the
> > target CPUs offline shortly but the policy is to be setup before VM
> > is launched, right?
> 
> Not always. Waiman mentioned the cpuset work earlier; it could
> cover selecting the policy before a new VM starts.
> 
> Some customers express a preference for host tick suppression
> through the management interface when changing workloads within
> a running VM. The host operator decides whether to allow
> suppression on the CPUs backing that VM.

I think people should know ahead if they will run latency critical workloads
or common workloads in their VMs. Because those are completely different.

> 
> We want to support revisiting that decision while keeping those
> CPUs online and the VM running, with nohz_full membership
> unchanged. Could such an operation fit into the cpuset work?

If that is really necessary then I guess we can have a file to control that
in cpuset once the nohz_full interface is ready. Though I'm a bit skeptical due
to the overhead of user <-> kernel transitions and housekeeping.

Thanks.

> 
> Thanks,
> Peng
> 
> > 
> > Thanks.
> > 
> > -- 
> > Frederic Weisbecker
> > SUSE Labs

-- 
Frederic Weisbecker
SUSE Labs