[Dovecot] Config review (2.0.5)

[Ralf Hildebrandt]

* Timo Sirainen <tss at iki.fi>:

> > My idea is to turn back on logging and then trace the dovecot/log
> > process using 
> > 
> > strace -p PID -c
> 
> -tt is also nice.

I traced around a bit today, in dovecot-lda. 
A pattern I'm seeing quite often is this:

     0.000853 open("/usr/dovecot-2/lib/dovecot/settings", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = 7
     0.000463 fcntl64(7, F_GETFD)       = 0x1 (flags FD_CLOEXEC)
     0.000555 getdents64(7, /* 8 entries */, 32768) = 360
     0.023219 getdents64(7, /* 0 entries */, 32768) = 0
     0.001545 close(7)                  = 0

two consecutive getdents64 calls on the same FD, one fast, one slow.
WTF?

# ll /usr/dovecot-2/lib/dovecot/settings
total 88
-rw-r--r-- 1 root root 24766 Okt 21 21:27 libmanagesieve_login_settings.a
-rwxr-xr-x 1 root root  1107 Okt 21 21:27 libmanagesieve_login_settings.la
-rwxr-xr-x 1 root root 23291 Okt 21 21:27 libmanagesieve_login_settings.so
-rw-r--r-- 1 root root 11630 Okt 21 21:27 libmanagesieve_settings.a
-rwxr-xr-x 1 root root  1065 Okt 21 21:27 libmanagesieve_settings.la
-rwxr-xr-x 1 root root 12858 Okt 21 21:27 libmanagesieve_settings.so

And this is happening once more in the same trace:

     0.002036 open("/usr/dovecot-2/lib/dovecot", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = 8
     0.000468 fcntl64(8, F_GETFD)       = 0x1 (flags FD_CLOEXEC)
     0.003281 getdents64(8, /* 85 entries */, 32768) = 3736
     0.150525 getdents64(8, /* 0 entries */, 32768) = 0
     0.000490 close(8)                  = 0

on fast call, one slow call.

Sorting all traces by execution time:

% cat dovecot-lda.* | sort -n -k1 |less
     0.094459 fstat64(8, {st_mode=S_IFREG|0755, st_size=1870288, ...}) = 0
     0.095051 brk(0x8d73000)            = 0x8d73000
     0.098191 getdents64(8, /* 0 entries */, 32768) = 0
     0.098912 time(NULL)                = 1288084930
     0.103059 getdents64(8, /* 0 entries */, 32768) = 0
     0.110251 getdents64(8, /* 0 entries */, 32768) = 0
     0.115710 getdents64(8, /* 0 entries */, 32768) = 0
     0.117688 time(NULL)                = 1288084937
     0.128360 getdents64(8, /* 0 entries */, 32768) = 0
     0.130091 mprotect(0xb75b4000, 4096, PROT_READ) = 0
     0.131681 rt_sigaction(SIGALRM, {0xb76cb490, [], SA_SIGINFO}, NULL, 8) = 0
     0.133327 getdents64(8, /* 0 entries */, 32768) = 0
     0.134047 stat64("/home/c/o/cousername/Maildir/dovecot-uidlist", {st_mode=S_IFREG|0600, st_size=1130, ...}) = 0
     0.135077 rt_sigaction(SIGPIPE, {SIG_IGN, [], SA_RESTART}, NULL, 8) = 0
     0.150525 getdents64(8, /* 0 entries */, 32768) = 0
     0.153457 open("/home/f/k/fkusername/Maildir/dovecot-uidlist", O_RDWR|O_LARGEFILE) = 11
     0.170190 getdents64(8, /* 0 entries */, 32768) = 0
     0.188536 getdents64(8, /* 0 entries */, 32768) = 0
     0.193665 umask(077)                = 0177
     0.270003 getdents64(8, /* 0 entries */, 32768) = 0
		    
-- 
Ralf Hildebrandt
  Geschäftsbereich IT | Abteilung Netzwerk
  Charité - Universitätsmedizin Berlin
  Campus Benjamin Franklin
  Hindenburgdamm 30 | D-12203 Berlin
  Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
  ralf.hildebrandt at charite.de | http://www.charite.de