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

From: Ingo Molnar
Date: Tue May 12 2015 - 08:34:54 EST

* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> On Tue, May 12, 2015 at 11:10:32AM +0200, Ingo Molnar wrote:
> >
> > 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...
> But why do we need a CONFIG flag for something that has no content?
> That is, I do not see anything much; except the 'I want to stay in
> userspace and kill me otherwise' flag, and I'm not sure that
> warrants a CONFIG flag like this.
> Other than that, its all a combination of NOHZ_FULL and
> cpusets/isolcpus and whatnot.

Yes, that's what I meant: CONFIG_ISOLATION would trigger what is
NO_HZ_FULL today - we could possibly even remove CONFIG_NO_HZ_FULL as
an individual Kconfig option?

CONFIG_ISOLATION=y would express the guarantee from the kernel that
it's possible for user-space to configure itself to run undisturbed -
instead of the current inconsistent set of options and facilities.

A bit like CONFIG_PREEMPT_RT is more than just preemptable spinlocks,
it also tries to offer various facilities and tune the defaults to
turn the kernel hard-rt.

Does that make sense to you?



To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at