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

[Peter Zijlstra]

On Fri, Oct 27, 2017 at 05:06:25AM -0700, tip-bot for Frederic Weisbecker wrote:
> +	isolcpus=	[KNL,SMP] Isolate a given set of CPUs from disturbance.
> +			Format: [flag-list,]<cpu-list>
> +
> +			Specify one or more CPUs to isolate from disturbances
> +			specified in the flag list (default: domain):
> +
> +			nohz
> +			  Disable the tick when a single task runs.
> +			domain
> +			  Isolate from the general SMP balancing and scheduling
> +			  algorithms. This option is the preferred way to isolate
> +			  CPUs from tasks. 

I _strongly_ object to this statement, isolcpus is _not_ the preferred
way, cpusets are.

And yes, while cpusets suffers some problems, we _should_ really fix
those and not promote this piece of shit isolcpus crap.

> The alternative -- manually setting the
> +			  CPU mask of all tasks in the system, can cause problems
> +			  and suboptimal load balancer performance. You can move a
> +			  process onto or off an "isolated" CPU via the CPU
> +			  affinity syscalls or cpuset. <cpu number> begins at 0
> +			  and the maximum value is "number of CPUs in system - 1".
> +
> +			The format of <cpu-list> is described above.
> +