slow directory operation on huge dirs

[Miroslav Lachman]

Wojciech Puchar wrote on 2020/01/23 12:45:
> 
> 
> On Sun, 19 Jan 2020, Wojciech Puchar wrote:
> 
>> i have UFS_DIRHASH enabled and enough large dirhash_maxmem
>> yet when there is heavy I/O on large directory (like dovecot indexing 
>> so it reads every file) it randomly works fast or slow. Most often slow.
>> Whole system slows down, and system cpu usage gets above 50% on quad 
>> core Xeon.
>>
>> lowering maxvnodes from 500000 to 100000 "fixes" the problem.
>>
>> what is going on here?
>>
>> 11.3-STABLE from maybe 2 weeks ago.
>>
> nobody have idea what's the problem?

Is it "just slow" or is your disk too busy? (iostat)

Can it be that pre-cacheing on huge directory makes disk too busy 
because there is too much to read?

Miroslav Lachman