Re: [PATCH 0/6] Optimize the cpu hotplug locking -v2

[Linus Torvalds]

On Thu, Oct 10, 2013 at 12:04 PM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> I'm wondering if we can have a for_each_cpu() that only disables
> preemption in the loop.

I think we'd generally want to have it be something the loop asks for.

If the loop is just some kind of "gather statistics" thing, I don't
think it's required. The cost per loop is so low (usually adding up a
couple of words) that the downside drowns the upside.

And we could easily look at MAXSMP (or NR_CPUS) at compile-time, and
not do it for common small values (although it looks like Fedora
defaults to 128 CPU's for their distro kernels, which seems a bit
excessive - too many by far for normal people, too few for the crazy
big ones).

                Linus
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