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SubjectRe: [PATCH 04/21] Generic percpu refcounting
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


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