Someone who's got data regarding this should file a bug report, it sounds like 
a quick fix for defaults if this holds true.

On Sat, May 20, 2023, at 00:59, Hector Martin wrote:
> On 17/05/2023 03.07, 胡 玮文 wrote:
>> Hi Sake,
>> 
>> We are experiencing the same. I set “osd_mclock_cost_per_byte_usec_hdd” to 
>> 0.1 (default is 2.6) and get about 15 times backfill speed, without 
>> significant affect client IO. This parameter seems calculated wrongly, from 
>> the description 5e-3 should be a reasonable value for HDD (corresponding to 
>> 200MB/s). I noticed this default is originally 5.2, then changed to 2.6 to 
>> increase the recovery speed. So I suspect the original author just convert 
>> the unit wrongly, he may want 5.2e-3 but wrote 5.2 in code.
>> 
>> But all this may be not important in the next version. I see the relevant 
>> code is rewritten, and this parameter is now removed.
>> 
>> high_recovery_ops profile works very poorly for us. It increase the average 
>> latency of client IO from 50ms to about 1s.
>> 
>> Weiwen Hu
>> 
>
> Thank you for this, that parameter indeed seems completely wrong
> (assuming it means what it says on the tin). After changing that my
> Quincy cluster is no recovering at a much more reasonable speed.
>
> - Hector
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