slow directory operation on huge dirs

[Wojciech Puchar]

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?