Re: [PATCH 1/2] scalable rw_mutex

[Andrew Morton]

On Sat, 12 May 2007 11:06:24 -0700 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:

> We could put a cpumask in percpu_counter, initialise it to
> cpu_possible_map.  Then, those callsites which have hotplug notifiers can
> call into new percpu_counter functions which clear and set bits in that
> cpumask and which drain percpu_counter.counts[cpu] into
> percpu_counter.count.
> 
> And percpu_counter_sum() gets taught to do for_each_cpu_mask(fbc->cpumask).

Perhaps we could have a single cpu hotplug notifier in the percpu_counter
library.  Add register/deregister functions to the percpu_counter API so
that all percpu_counters in the machine can be linked together.

One _could_ just register and deregister the counters in
percpu_counter_init() and percpu_counter_destroy(), but perhaps that
wouldn't suit all callers, dunno.

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