Re: [tip:sched/core] sched/isolation: Document the isolcpus= flags

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

On Mon, Oct 30, 2017 at 11:30:59AM -0500, Christopher Lameter wrote:
> Historically cpusets were not used for cpu isolation. They were used to
> restrict applications threads to sets of cpus for performance reasons. And
> we are here dealing with individual processors.

The HPC workloads very much disabled load-balancing across most CPUs. If
you disable "sched_load_balance" the thing creates NULL sched_domains,
the exact thing isolcpus ends up doing.

This is something cpusets have done for a _long_ time, if not from the
very start.

Yes, you can also create smaller sched_domains which is useful for other
cases and you can even mix the lot, by creating a small set of
load-balanced CPUs for the system tasks while giving a bunch of
unbalanced CPUs to your application.

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