Re: [PATCH 04/21] Generic percpu refcounting

[Tejun Heo <tj@kernel.org>]

Hello, again, continuing the brain diarrehea,

On Tue, May 14, 2013 at 02:59:45PM -0700, Tejun Heo wrote:
> So, while I do like the simplicity of put() returning %true on the
> final put, I suspect it's more likely to slowing down fast paths due
> to its interface compared to having separate ->release function
> combined with void put().  Any ideas?

Maybe we can structure put in a way that's difficult to get wrong for
the compiler?

	bool put()
	{
		preempt_disable();
		if (likely(not killed yet)) {
			this_cpu_dec();
			preempt_enable();
			return false;
		}
		return put_slowpath();
	}

This doesn't solve the caller not inlining hot path but well I suppose
we can consider that the caller's problem.  The above at least
wouldn't introduce an unnecessary branch on its own.

Thanks.

-- 
tejun