Re: [PATCH v2 2/4] percpu_stats: Enable 64-bit counts in 32-bit architectures

Tejun Heo
2016-04-11T22:17:06Z

Hello, Waiman.

On Fri, Apr 08, 2016 at 02:45:38PM -0400, Waiman Long wrote:
> The percpu_stats construct allows minimal overhead in maintaining statistics
> counts. The percpu_counter construct, on the other hand, has a higher
> performance overhead and a bit more complex to set up and tear down when

If you're referring to the preemption on/off, as I wrote before, we'll
probably be able to improve that with this_cpu_add_return so that the
only extra overhead is an easily predictable branch which is extremely
cheap. It's better to improve common constructs anyway.

> more than one statistics counts are needed. In fact, my first draft of the

And yeah, it can be cumbersome to set up and tear down multiple
percpu_counters. If there are enough consumers, we can extend
percpu_counter to handle multiple counters, right?

Thanks.

--
tejun