Slow reading of large dovecot-uidlist files

Bostjan Skufca bostjan at
Sat Apr 9 18:04:14 UTC 2016

Hi there,

(context: I was optimizing Roundcube mailbox list server response, and in
that 300-400ms response time, around 170ms is spent on single fgets() call
which is waiting IMAP repsonse to "SELECT MyMailbox" command)

I straced dovecot and of the whole request/response process, around 30ms is
spent for everything else, and overwhelming majority of time (150-170ms) is
spent for reading dovecot-uidlist file for given mailbox.

I skimmed over src/lib-storage/index/maildir/maildir-uidlist.c
and src/src/lib/istream.c, but I am out of ideas on how to optimize
mentioned file reading elegantly to make it faster.

Is there any way to cache parsed content of uidlist file(s) or some other
obvious quicktrick I am missing to speed this process up?

Does anyone have any other ideas, how to speed this up?


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