slow directory operation on huge dirs

[Miroslav Lachman]

Wojciech Puchar wrote on 2020/01/23 14:12:
>>>>
>>> nobody have idea what's the problem?
>>
>> Is it "just slow" or is your disk too busy? (iostat)
> 
> no. disk is idle, system CPU load takes half of system (8 cores)!
> 
>>
>> Can it be that pre-cacheing on huge directory makes disk too busy 
>> because there is too much to read?
> this part works fine. The problem begins where it's already cached.
> 
> To get the problem you need BOTH of:
> 
> - large maxvnodes like half million
> - large directory (in order of 100000 files)

I remember very similar problem with slow access of directories with 80 
000+ files. It was always slow like frozen hell. There is some 
recommendation to avoid more than 10 000 of file entries in a directory. 
That is why filesystem caches or sessions in PHP must create more levels 
of subdirectories.
I know you cannot control users of maildirs.
I am not sure if this situation can be improved or not.

Miroslav Lachman