Re: [PATCH v2 0/3] blk-mq: Optimise blk_mq_queue_tag_busy_iter() for shared tags

[John Garry]

On 06/12/2021 19:07, Jens Axboe wrote:
> On 12/6/21 5:49 AM, John Garry wrote:
> > In [0] Kashyap reports high CPU usage for blk_mq_queue_tag_busy_iter()
> > and callees for shared tags.
> >
> > Indeed blk_mq_queue_tag_busy_iter() would be less optimum for moving to
> > shared tags, but it was not optimum previously.
> >
> > This series optimises by having only a single iter (per regular and resv
> > tags) for the shared tags, instead of an iter per HW queue.
> >
> > [0]https://lore.kernel.org/linux-block/e4e92abbe9d52bcba6b8cc6c91c442cc@xxxxxxxxxxxxxx/

Hi Jens,

> The patch(es) are missing Fixes tags.

The first two patches aren't fixes, but are general dev. As for the 
last, it prob should go as a fix for 5.16, but I was not sure how you 
would feel about that - it's not a trivial change, we're late in the 
cycle, and Kashyap was happy for 5.17 .

Let me know if the last could be accepted as a fix and I'll re-send 
separately with a fixes tag.

Thanks,
John