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

[Waiman Long]

On 04/07/2016 04:41 PM, Tejun Heo wrote:
> 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.

In this case, I think I will drop this reset functionality. It is not 
really needed for this patchset.

Thanks for the feedback!

Cheers,
Longman