Re: [PATCH] blk-mq: allow hardware queue to get more tag while sharing a tag set

[Bart Van Assche]

On 7/11/21 8:18 PM, Yu Kuai wrote:
> If there are multiple active queues while sharing a tag set, it's not
> necessary to limit the available tags as same share for each active queue
> if no one ever failed to get driver tag. And fall back to same share if
> someone do failed to get driver tag.
> 
> This modification will be beneficial if total queue_depth of disks
> on the same host is less than total tags.

This patch adds new atomic operations in the hot path and hence probably
has a negative performance impact. What is the performance impact of
this patch for e.g. null_blk when submitting I/O from all CPU cores?

Thanks,

Bart.