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

[Jens Axboe]

On 12/5/18 11:03 AM, Mike Snitzer wrote:
> 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.

The incremental should be done first in that case, it'd be silly to
introduce something only to do a cleanup right after.


-- 
Jens Axboe