[Dovecot] maildirsize quota counting locking account?

Hi,

I've just straced a dovecot imap process and found one thread sitting there doing hundreds and hundreds of maildirsize updates as follows:

open("/home/virtual/mydomain.com/home/admin/Maildir/maildirsize", O_RDWR|O_APPEND) = 7 read(7, "10485760000S\n1562717408 107547\n-"..., 5120) = 2446 read(7, "", 2674) = 0 write(1, "* 1810 FETCH (UID 1815 RFC822.SI"..., 2031) = 2031 setsockopt(1, SOL_TCP, TCP_CORK, [0], 4) = 0 epoll_wait(4, {{EPOLLIN, {u32=101056896, u64=2370923004288}}}, 5, 2584) = 1 read(0, "2838 UID fetch 1816 (UID RFC822."..., 2974) = 51 setsockopt(1, SOL_TCP, TCP_CORK, [1], 4) = 0 close(7) = 0 open("/home/virtual/mydomain.com/home/admin/Maildir/maildirsize", O_RDWR|O_APPEND) = 7 read(7, "10485760000S\n1562717408 107547\n-"..., 5120) = 2446 read(7, "", 2674) = 0 open("/home/virtual/mydomain.com/home/admin/Maildir/.Folders.ALERTS.Payments/cur/1195331425.M52296P11937V0000000000000807I000000001015A5EB_0.tg3,S=2079:2,Sa", O_RDONLY) = 10 fstat(10, {st_mode=S_IFREG|0600, st_size=2079, ...}) = 0 pread(10, "Return-Path:

During this time (at least 5-10 minutes) , I could not check the account via my email client Thunderbird. Clicking on an email would just sit there as if it is loading but nothing would happen - the read pane just remains blank.

Is Dovecot going through every email (of many 10,000's) and counting up the sizes? Could this be made more efficient so it doesn't lock the account?

This could I guess be a Thunderbird issue - it is a disappointingly imperfect client.

Dan