Re: [PATCH 09/40] autonuma: introduce kthread_bind_node()

From: Glauber Costa
Date: Thu Jul 05 2012 - 14:36:35 EST

On 07/05/2012 05:09 PM, Johannes Weiner wrote:
> In the very first review iteration of AutoNUMA, Peter argued that the
> scheduler people want to use this flag in other places where they rely
> on this thing meaning a single cpu, not a group of them (check out the
> cpumask test in debug_smp_processor_id() in lib/smp_processor_id.c).
> He also argued that preventing root from rebinding the numa daemons is
> not critical to this feature at all. And I have to agree.

Despite not being a scheduler expert, I'll have to side with that as
well. The thing I have in mind is: We have people whose usecase depend
on completely isolating cpus, with nothing but a specialized task
running on it. For those people, even the hard binding between cpu0 and
the timer interrupt is a big problem.

If you force a per-node binding of a kthread, you are basically saying
that those people are unable to isolate a node. Or else, that they have
to choose between that, and AutoNUMA. Both are suboptimal choices, to
say the least.

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