performance issue with UID SEARCH

[Aki Tuomi]

Without FTS, dovecot needs to open *each* and *every* email when doing
text searches, which is understandably rather slow process.

Aki

On 27.2.2019 10.43, Marc Roos wrote:
>  
>
> I am not sure if this any help. From what I understand of maildir it has 
> lots of separate files, thus uid/gid lookups. Try running something like 
> nscd, that will cache these lookups?
>
>
>
>
> -----Original Message-----
> From: Aki Tuomi via dovecot [mailto:dovecot at dovecot.org] 
> Sent: 27 February 2019 06:24
> To: Ben Burke; Dovecot Mailing List
> Subject: Re: performance issue with UID SEARCH
>
>
> 	On 27 February 2019 03:27 Ben Burke via dovecot < 
> dovecot at dovecot.org> wrote: 
>
>
> 	Hi, 
>
> 	I'm running dovecot 2.2.x and I'm having an issue where I see many 
> 	dovecot processes use all the available IO on a server. According 
> to 
> 	iotop the worst offenders seem to be in this state (NOTE: I swapped 
> in 
> 	phony username & IP info): 
>
> 	dovecot/imap [someusername 123.456.789.012 UID SEARCH] 
>
> 	The server in question is running with Maildirs on top of an XFS 
> 	filesystem. Is there anything I can do to optimize "UID SEARCH" or 
> find 
> 	out why it's being a problem? I've read 
> 	https://wiki2.dovecot.org/PerformanceTuning and the linked pages. 
>
> 	By "being a problem" I mean iostat -xmt 1 /dev/diskdevice shows 
> 100% 
> 	utilization for long periods and in some cases io service times are 
>
> 	taking many seconds... which causes thunderbird to timeout when 
> doing 
> 	things like appending messages to user "Sent" mailboxes. 
>
> 	Any ideas? 
>
> 	Thanks, 
> 	Ben Burke 
>
>
> Are you using FTS? If not, you should. See 
> https://wiki.dovecot.org/Plugins/FTS
> ---
> Aki Tuomi
>
>