[Drbd-dev] [RFC for-6.2/block V2] block: Change the granularity of io ticks from ms to ns

[Keith Busch]

On Wed, Dec 07, 2022 at 11:17:12PM +0000, Chaitanya Kulkarni wrote:
> On 12/7/22 15:08, Jens Axboe wrote:
> > 
> > My default peak testing runs at 122M IOPS. That's also the peak IOPS of
> > the devices combined, and with iostats disabled. If I enabled iostats,
> > then the performance drops to 112M IOPS. It's no longer device limited,
> > that's a drop of about 8.2%.
> > 
> 
> Wow, clearly not acceptable that's exactly I asked for perf
> numbers :).

For the record, we did say per-io ktime_get() has a measurable
performance harm and should be aggregated.

  https://www.spinics.net/lists/linux-block/msg89937.html