Messages in this thread | | | Date | Thu, 10 Oct 2013 15:34:34 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH 0/6] Optimize the cpu hotplug locking -v2 |
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On Thu, 10 Oct 2013 12:16:16 -0700 Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Thu, Oct 10, 2013 at 12:04 PM, Steven Rostedt <rostedt@goodmis.org> 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.
Yeah, I was thinking of adding a new macro, not update for_each_cpu() itself, so that only the locations that would require it would use it.
> > 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).
We could always make it a boot time option, and use alternates to change the code as we do with spin_locks() and other code.
-- Steve (the lover of self modifying code)
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