CONFIG_ISOLATION=y (was: [PATCH 0/6] support "dataplane" mode for nohz_full)

* Chris Metcalf [off-list ref] wrote:

- ISOLATION (Frederic).  I like this but it conflicts with other uses
  of "isolation" in the kernel: cgroup isolation, lru page isolation,
  iommu isolation, scheduler isolation (at least it's a superset of
  that one), etc.  Also, we're not exactly isolating a task - often
  a "dataplane" app consists of a bunch of interacting threads in
  userspace, so not exactly isolated.  So perhaps it's too confusing.

So I'd vote for Frederic's CONFIG_ISOLATION=y, mostly because this is 
a high level kernel feature, so it won't conflict with isolation 
concepts in lower level subsystems such as IOMMU isolation - and other 
higher level features like scheduler isolation are basically another 
partial implementation we want to merge with all this...

nohz, RCU tricks, watchdog defaults, isolcpus and various other 
measures to keep these CPUs and workloads as isolated as possible
are (or should become) components of this high level concept.

Ideally CONFIG_ISOLATION=y would be a kernel feature that has almost 
zero overhead on normal workloads and on non-isolated CPUs, so that 
Linux distributions can enable it.

Enabling CONFIG_ISOLATION=y should be the only 'kernel config' step 
needed: just like cpusets, the configuration of isolated CPUs should 
be a completely boot option free excercise that can be dynamically 
done and undone by the administrator via an intuitive interface.

Thanks,

	Ingo