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

From: Ingo Molnar
Date: Tue May 12 2015 - 05:11:01 EST

* Chris Metcalf <cmetcalf@xxxxxxxxxx> 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.


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