performance issue with UID SEARCH
aki.tuomi at open-xchange.com
Wed Feb 27 14:12:40 EET 2019
Without FTS, dovecot needs to open *each* and *every* email when doing
text searches, which is understandably rather slow process.
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:
> 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
> iotop the worst offenders seem to be in this state (NOTE: I swapped
> 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
> 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
> utilization for long periods and in some cases io service times are
> taking many seconds... which causes thunderbird to timeout when
> things like appending messages to user "Sent" mailboxes.
> Any ideas?
> Ben Burke
> Are you using FTS? If not, you should. See
> Aki Tuomi
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