Re: [PATCH v2 2/3] mm: page_counter: rearrange struct page_counter fields

[Andrew Morton]

On Wed, 24 Aug 2022 21:41:42 -0700 Shakeel Butt <shakeelb@xxxxxxxxxx> wrote:

> > Did you evaluate the effects of using a per-cpu counter of some form?
> 
> Do you mean per-cpu counter for usage or something else?

percpu_counter, perhaps.  Or some hand-rolled thing if that's more suitable.

> The usage
> needs to be compared against the limits and accumulating per-cpu is
> costly particularly on larger machines,

Well, there are tricks one can play.  For example, only run
__percpu_counter_sum() when `usage' is close to its limit.  

I'd suggest flinging together a prototype which simply uses
percpu_counter_read() all the time.  If the performance testing results
are sufficiently promising, then look into the accuracy issues.