Re: [PATCH 2/3] percpu_stats: Simple per-cpu statistics count helper functions

[Tejun Heo <tj@kernel.org>]

Hello, Waiman.

On Thu, Apr 07, 2016 at 04:37:06PM -0400, Waiman Long wrote:
> I would say that because I am lazy, I don't want compute the deltas every
> time I want to see the effect of running a certain type of workload on the
> statistics counts. I have use case that I need to track 10 or so statistics
> counts and monitor their changes after running a job. It is much more
> convenient to do a reset and see what you get than doing manual subtractions
> to find out.

I don't know.  Write a simple script?  Even if you wanna keep it in
kernel, you can just have a base counter which offsets the summed up
value on read.

> I had taken a look at percpu-refcount.[ch]. I think the synchronization code
> is a bit overkill for this purpose as no one really need a very precise
> statistics counts nor precise atomic reset. I would prefer providing an
> optional atomic reset feature with slower statistics count update path for
> the time being. If we come across a use case where we need atomic reset with
> negligible slowdown, we could then refactor the code to use something
> similar to  what the percpu-refcount code is doing.

Please either drop reset or make it actually work; otherwise, I don't
think this should go in.

Thanks.

-- 
tejun