Messages in this thread | | | Date | Fri, 25 Apr 2008 23:28:41 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH 1/11] Add generic helpers for arch IPI function calls |
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Jens Axboe wrote: > On Thu, Apr 24 2008, Russell King wrote: > >> On Tue, Apr 22, 2008 at 08:50:17PM +0200, Jens Axboe wrote: >> >>> + data->csd.func(data->csd.info); >>> + >>> + spin_lock(&data->lock); >>> + cpu_clear(cpu, data->cpumask); >>> + WARN_ON(data->refs == 0); >>> + data->refs--; >>> + refs = data->refs; >>> >> Probably a silly question, but what does data->refs do that >> cpus_empty(data->cpumask) wouldn't do? (as indeed ARM presently does.) >> > > I guess it can be marginally slower for NR_CPUS > BITS_PER_LONG, > otherwise there's absolutely no reason to have a seperate ref counter. >
Jes was concerned about scanning bitmasks on a 4096 CPU Altix. I'm not sure its all that important, but a refcount check would definitely be quicker.
J
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