Re: [PATCH v2] blk-wbt: fix performance regression in wbt scale_up/scale_down

[Jens Axboe]

On 10/5/19 12:59 PM, Harshad Shirwadkar wrote:
> scale_up wakes up waiters after scaling up. But after scaling max, it
> should not wake up more waiters as waiters will not have anything to
> do. This patch fixes this by making scale_up (and also scale_down)
> return when threshold is reached.
> 
> This bug causes increased fdatasync latency when fdatasync and dd
> conv=sync are performed in parallel on 4.19 compared to 4.14. This
> bug was introduced during refactoring of blk-wbt code.

Nice catch, thanks, applied.

-- 
Jens Axboe