Memory leaks?

[Frédéric Fauberteau <triaxx%NetBSD.org@localhost>]

Hi all,

I realized that I do not really know how memory works. I recently found 
my mail server was very slow and when I looked at the memory usage with 
htop, I noticed that NetBSD was swapping. I though that ~4 GB of memory 
was sufficient for programs that I considered light: Postfix, Dovecot, 
OpenSSH, NGINX (only for proxy). I think the fatest program is Rspamd.

When I boot the VM, the memory usage is correct: 218M. I do not know 
what the SIZE column is. The manual of top says it is the total size of 
the process. I am surprised that an instance of sshd is about 80 MB. I 
see the RES column seems more consistent with what I could expect: 4368 
KB for sshd seems correct. My question is probably naive, but what is 
the difference? What could sshd do with 76 MB of memory?

load averages:  0.23,  0.12,  0.05;               up 0+00:03:39          
                                     09:34:55
61 processes: 59 sleeping, 2 on CPU
CPU states:  0.1% user,  0.0% nice,  0.4% system,  0.1% interrupt, 99.4% 
idle
Memory: 218M Act, 112K Wired, 25M Exec, 111M File, 3661M Free
Swap: 8192M Total, 8192M Free

  PID USERNAME PRI NICE   SIZE   RES STATE      TIME   WCPU    CPU 
COMMAND
  881 rspamd    85    0   162M   15M kqueue/0   0:00  0.00%  0.00% 
rspamd-2.1
  652 rspamd    85    0   161M   11M kqueue/0   0:00  0.00%  0.00% 
rspamd-2.1
  670 rspamd    85    0   161M   10M kqueue/0   0:00  0.00%  0.00% 
rspamd-2.1
  758 root      85    0   160M 7168K kqueue/1   0:00  0.00%  0.00% 
rspamd-2.1
 1037 root      85    0   116M 8908K nanosl/1   0:03  0.00%  0.00% perl
  104 rrdcache  43    0   116M 2840K parked/0   0:00  0.00%  0.00% 
rrdcached
   75 postfix   85    0    80M 7940K kqueue/0   0:00  0.00%  0.00% smtpd
   66 root      85    0    80M 5856K select/1   0:00  0.00%  0.00% sshd
 1198 triaxx    85    0    80M 4368K select/0   0:00  0.00%  0.00% sshd
 1108 triaxx    85    0    80M 4384K select/0   0:00  0.00%  0.00% sshd
  370 root      85    0    80M 5848K select/0   0:00  0.00%  0.00% sshd
 1260 triaxx    85    0    80M 4360K select/1   0:00  0.00%  0.00% sshd
 1021 root      85    0    80M 5852K select/1   0:00  0.00%  0.00% sshd
  130 postfix   85    0    79M 8008K lockf/0    0:00  0.00%  0.00% smtpd
  354 postfix   85    0    79M 8020K lockf/0    0:00  0.00%  0.00% smtpd
   73 postfix   85    0    79M 7972K kqueue/1   0:00  0.00%  0.00% smtpd
 1095 postfix   85    0    79M 7952K lockf/0    0:00  0.00%  0.00% smtpd
 1023 postfix   85    0    79M 6544K kqueue/0   0:00  0.00%  0.00% 
tlsmgr
 1111 root      85    0    75M 4136K kqueue/1   0:00  0.00%  0.00% 
master
  581 postfix   85    0    75M 6188K kqueue/1   0:00  0.00%  0.00% qmgr
  989 postfix   85    0    75M 6212K kqueue/0   0:00  0.00%  0.00% anvil
  853 postfix   85    0    75M 6196K kqueue/1   0:00  0.00%  0.00% 
proxymap

After some days (~7), I get a more problematic memory usage. I see that 
rspamd took a little weight, but it is not alarming. However, I have now 
2647 MB of active memory and 2328 of them are for files. I would be very 
grateful of any advice that could help me to understand what is the 
issue and which program consumes so much memory.

load averages:  0.04,  0.07,  0.07;               up 7+05:18:48          
                                     09:29:51
68 processes: 66 sleeping, 2 on CPU
CPU states:  0.6% user,  0.0% nice,  1.0% system,  0.0% interrupt, 98.4% 
idle
Memory: 2647M Act, 1308K Inact, 132K Wired, 115M Exec, 2328M File, 818M 
Free
Swap: 8192M Total, 8192M Free

  PID USERNAME PRI NICE   SIZE   RES STATE      TIME   WCPU    CPU 
COMMAND
  891 rspamd    85    0   255M  120M kqueue/0   0:21  0.05%  0.05% 
rspamd-1.9.4
  824 rspamd    85    0   163M   13M kqueue/1   0:26  0.00%  0.00% 
rspamd-1.9.4
  719 rspamd    85    0   163M   15M kqueue/0    ???  0.00%  0.00% 
rspamd-1.9.4
  697 root      85    0   161M 7680K kqueue/1   0:01  0.00%  0.00% 
rspamd-1.9.4
  870 rrdcache  43    0   118M 2852K parked/0    ???  0.00%  0.00% 
rrdcached
  169 root      85    0   116M 9172K nanosl/0    ???  0.00%  0.00% perl
 1108 triaxx    85    0    83M 4324K select/0    ???  0.00%  0.00% sshd
   74 root      85    0    82M 5788K select/0   0:00  0.00%  0.00% sshd
  137 triaxx    85    0    81M 4336K select/0    ???  0.00%  0.00% sshd
  418 root      85    0    80M 5796K select/1   0:00  0.00%  0.00% sshd
21804 triaxx    85    0    80M 4388K select/0   0:01  0.00%  0.00% sshd
15853 root      85    0    80M 5892K select/1   0:00  0.00%  0.00% sshd
  773 triaxx    85    0    80M 4396K select/0   2:26  0.00%  0.00% sshd
 1060 root      85    0    80M 5804K select/0   0:00  0.00%  0.00% sshd
24791 postfix   85    0    79M 8408K lockf/0    0:00  0.00%  0.00% smtpd
29154 postfix   85    0    79M 8376K select/0    ???  0.00%  0.00% smtpd
28912 postfix   85    0    79M 8328K kqueue/1    ???  0.00%  0.00% smtpd
21134 postfix   85    0    79M 8312K lockf/0     ???  0.00%  0.00% smtpd
 7654 postfix   85    0    79M 8100K select/0    ???  0.00%  0.00% smtpd
12732 postfix   85    0    79M 8092K kqueue/0    ???  0.00%  0.00% smtpd
27146 postfix   85    0    79M 8328K select/0    ???  0.00%  0.00% smtpd
 1085 postfix   85    0    79M 6584K kqueue/1   0:01  0.00%  0.00% 
tlsmgr