[dm-devel] [PATCH v2 4/6] block: switch to per-cpu in-flight counters

[Mike Snitzer]

On Wed, Dec 05 2018 at 12:54pm -0500,
Jens Axboe <axboe at kernel.dk> wrote:

> On 12/5/18 10:49 AM, Mike Snitzer wrote:
> > On Wed, Dec 05 2018 at 12:30pm -0500,
> > Jens Axboe <axboe at kernel.dk> wrote:
> > 
> >> There's also no need to pass in the cpu, if we're not running with
> >> preempt disabled already we have a problem. 
> > 
> > Why should this be any different than the part_stat_* interfaces?
> > __part_stat_add(), part_stat_read(), etc also use
> > per_cpu_ptr((part)->dkstats, (cpu) accessors.
> 
> Maybe audit which ones actually need it? To answer the specific question,
> it's silly to pass in the cpu, if we're pinned already. That's true
> both programatically, but also for someone reading the code.

I understand you'd like to avoid excess interface baggage.  But seems to
me we'd be better off being consistent, when extending the percpu
portion of block core stats, and then do an incremental to clean it all
up.

But I'm open to doing it however you'd like if you feel strongly about
how this should be done.

Mike