Re: [PATCH v16 12/26] block: Rework request allocation in blk_mq_submit_bio()

Damien Le Moal
2024-11-19T07:44:59Z

On 11/19/24 09:28, Bart Van Assche wrote:
> Prepare for allocating a request from a specific hctx by making
> blk_mq_submit_bio() allocate a request later.
>
> The performance impact of this patch on the hot path is small: if a
> request is cached, one percpu_ref_get(&q->q_usage_counter) call and one
> percpu_ref_put(&q->q_usage_counter) call are added to the hot path.
>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>

The patch looks OK, but I cannot weight on if this is really a "small" impact on
performance. Jens may want to run his perf setup with this to verify.

--
Damien Le Moal
Western Digital Research