Re: [PATCH 0/4] blk-mq: support to use hw tag for scheduling

Jens Axboe
2017-04-28T20:29:18Z

On 04/28/2017 09:15 AM, Ming Lei wrote:
> Hi,
>
> This patchset introduces flag of BLK_MQ_F_SCHED_USE_HW_TAG and
> allows to use hardware tag directly for IO scheduling if the queue's
> depth is big enough. In this way, we can avoid to allocate extra tags
> and request pool for IO schedule, and the schedule tag allocation/release
> can be saved in I/O submit path.

Ming, I like this approach, it's pretty clean. It'd be nice to have a
bit of performance data to back up that it's useful to add this code,
though. Have you run anything on eg kyber on nvme that shows a
reduction in overhead when getting rid of separate scheduler tags?

--
Jens Axboe