[Dovecot] getdents() with 4KB buffer - seems slow (Maildir, large inbox)

[Timo Sirainen]

On Mon, 2010-08-30 at 17:38 +0200, Marinos Yannikos wrote:

> I have a very large inbox (~146K mails) in Maildir format and dovecot
> seems to spend a lot of time rescanning the directory, especially when
> the server is loaded. I'm not sure whether this is triggered by
> Thunderbird or done regularly, but it takes longer when the server is
> loaded, so sometimes it seems that it is scanning continuously. 

You could see if maildir_very_dirty_syncs=yes is helpful.

> Since
> it takes around 2000 getdents64() syscalls to scan my inbox, I'm
> wondering whether the buffer size is a bit small with 4KB and might
> benefit from being configurable:

getdents64() is an internal kernel function and shouldn't be called
directly (Dovecot uses readdir(), which is implemented with
getdents64()). Also I doubt the buffer size is configurable and it
probably wouldn't even help if a larger one was used, 2000 isn't yet
that many syscalls.