Inexplicável alto uso de memória (aparentemente não causado por programas, buffers, cache ou cache slab)

1

Eu tenho um servidor que reivindica 1.7 de seus 2 GB de RAM, mas o uso de memória combinada dos processos em execução não chega nem perto desse valor:

$ free -m
             total       used       free     shared    buffers     cached
Mem:          1993       1898         94          0          0        199
-/+ buffers/cache:       1699        294
Swap:         2046         40       2006

$ grep VmRSS /proc/*/status | awk '{s+=$2} END {print s}'  
29080

Até agora, as explicações que encontrei culpam o alto uso de RAM em caches e buffers ou o cache slab do kernel , mas nenhum desses parece ser o motivo neste caso (veja também /proc/meminfo abaixo).

O que mais poderia estar causando esse uso excessivo de RAM (o que geralmente faz com que o sistema inicie a troca, mesmo com vm.swappiness = 1)?
O que posso fazer para encontrar e talvez mitigar o motivo?

Informação potencialmente relevante:
O sistema é um servidor dedicado alugado com um CPU Intel Atom N2800 e 2 GB de RAM, como visto acima. Ele está executando o Debian Wheezy (7.6) com o kernel 3.13 do wheezy-backports.
Seu atual /proc/meminfo :

MemTotal:        2041464 kB
MemFree:           95224 kB
Buffers:              20 kB
Cached:           204240 kB
SwapCached:        13000 kB
Active:           100280 kB
Inactive:         132036 kB
Active(anon):      15496 kB
Inactive(anon):    12580 kB
Active(file):      84784 kB
Inactive(file):   119456 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:       2096124 kB
SwapFree:        2054960 kB
Dirty:                64 kB
Writeback:             0 kB
AnonPages:         17208 kB
Mapped:             6888 kB
Shmem:                20 kB
Slab:              31180 kB
SReclaimable:      14628 kB
SUnreclaim:        16552 kB
KernelStack:        1848 kB
PageTables:         4556 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     3116856 kB
Committed_AS:     122748 kB
VmallocTotal:   34359738367 kB
VmallocUsed:       81792 kB
VmallocChunk:   34359611556 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      136108 kB
DirectMap2M:     1943552 kB

ps -eo pid,user,args,pmem --sort pmem , como Braiam solicitou:

  PID USER     COMMAND                     %MEM
    2 root     [kthreadd]                   0.0
    3 root     [ksoftirqd/0]                0.0
    5 root     [kworker/0:0H]               0.0
    7 root     [rcu_sched]                  0.0
    8 root     [rcu_bh]                     0.0
    9 root     [migration/0]                0.0
   10 root     [watchdog/0]                 0.0
   11 root     [watchdog/1]                 0.0
   12 root     [migration/1]                0.0
   13 root     [ksoftirqd/1]                0.0
   15 root     [kworker/1:0H]               0.0
   16 root     [watchdog/2]                 0.0
   17 root     [migration/2]                0.0
   18 root     [ksoftirqd/2]                0.0
   20 root     [kworker/2:0H]               0.0
   21 root     [watchdog/3]                 0.0
   22 root     [migration/3]                0.0
   23 root     [ksoftirqd/3]                0.0
   25 root     [kworker/3:0H]               0.0
   26 root     [khelper]                    0.0
   27 root     [kdevtmpfs]                  0.0
   28 root     [netns]                      0.0
   29 root     [writeback]                  0.0
   30 root     [kintegrityd]                0.0
   31 root     [bioset]                     0.0
   32 root     [kblockd]                    0.0
   35 root     [khungtaskd]                 0.0
   36 root     [kswapd0]                    0.0
   37 root     [ksmd]                       0.0
   38 root     [khugepaged]                 0.0
   39 root     [fsnotify_mark]              0.0
   40 root     [crypto]                     0.0
   45 root     [kthrotld]                   0.0
   46 root     [deferwq]                    0.0
  151 root     [khubd]                      0.0
  156 root     [ata_sff]                    0.0
  168 root     [scsi_eh_0]                  0.0
  170 root     [scsi_eh_1]                  0.0
  171 root     [scsi_eh_2]                  0.0
  172 root     [scsi_eh_3]                  0.0
  191 root     [kworker/3:1H]               0.0
  192 root     [kworker/1:1H]               0.0
  193 root     [kworker/0:1H]               0.0
  197 root     [kworker/2:1H]               0.0
  212 root     [bioset]                     0.0
  218 root     [btrfs-genwork-1]            0.0
  219 root     [btrfs-submit-1]             0.0
  220 root     [btrfs-delalloc-]            0.0
  221 root     [btrfs-fixup-1]              0.0
  224 root     [btrfs-rmw-1]                0.0
  225 root     [btrfs-endio-rai]            0.0
  226 root     [btrfs-endio-met]            0.0
  228 root     [btrfs-freespace]            0.0
  230 root     [btrfs-cache-1]              0.0
  231 root     [btrfs-readahead]            0.0
  233 root     [btrfs-qgroup-re]            0.0
  234 root     [btrfs-cleaner]              0.0
  235 root     [btrfs-transacti]            0.0
  415 root     [kworker/2:2]                0.0
  533 root     [kpsmoused]                  0.0
  619 root     [kworker/3:0]                0.0
 1383 root     [btrfs-genwork-1]            0.0
 1384 root     [btrfs-submit-1]             0.0
 1385 root     [btrfs-delalloc-]            0.0
 1386 root     [btrfs-fixup-1]              0.0
 1389 root     [btrfs-rmw-1]                0.0
 1390 root     [btrfs-endio-rai]            0.0
 1391 root     [btrfs-endio-met]            0.0
 1393 root     [btrfs-freespace]            0.0
 1395 root     [btrfs-cache-1]              0.0
 1396 root     [btrfs-readahead]            0.0
 1398 root     [btrfs-qgroup-re]            0.0
 1399 root     [btrfs-cleaner]              0.0
 1400 root     [btrfs-transacti]            0.0
 1687 root     /usr/sbin/sshd               0.0
 2087 root     [kworker/1:0]                0.0
 2218 root     [kworker/u8:0]               0.0
 2470 root     tmux                         0.0
 2473 root     -bash                        0.0
 4643 root     tmux a                       0.0
 6072 root     [kworker/u8:1]               0.0
 7126 root     [btrfs-worker-2]             0.0
14524 root     [btrfs-delayed-m]            0.0
16555 root     [kworker/0:2]                0.0
20514 root     [btrfs-flush_del]            0.0
22924 root     [btrfs-endio-2]              0.0
23031 root     [btrfs-worker-3]             0.0
26010 root     [btrfs-endio-3]              0.0
26227 root     [btrfs-endio-met]            0.0
26383 root     [btrfs-delayed-m]            0.0
26823 root     [btrfs-endio-wri]            0.0
27063 root     [btrfs-endio-met]            0.0
28637 root     [kworker/0:0]                0.0
30011 root     [kworker/2:0]                0.0
30832 root     [btrfs-flush_del]            0.0
31387 root     [kworker/1:2]                0.0
31475 root     [kworker/3:2]                0.0
31803 root     [btrfs-endio-wri]            0.0
32361 root     [kworker/1:1]                0.0
  499 root     lxc-start -d -n io           0.0
 1682 sshd     /usr/bin/dbus-daemon --syst  0.0
 2181 mail     /usr/sbin/nullmailer-send -  0.0
13533 root     -bash                        0.0
19059 root     lxc-start -n callisto -d     0.0
20446 root     /usr/sbin/sshd               0.0
20693 root     /usr/sbin/acpid              0.0
 1708 root     /sbin/getty 38400 console    0.0
 1709 root     /sbin/getty 38400 tty1 linu  0.0
 1710 root     /sbin/getty 38400 tty2 linu  0.0
 1711 root     /sbin/getty 38400 tty3 linu  0.0
 1712 root     /sbin/getty 38400 tty4 linu  0.0
 1832 root     -bash                        0.0
 2276 root     /sbin/getty 38400 tty1       0.0
 2277 root     /sbin/getty 38400 tty2       0.0
 2278 root     /sbin/getty 38400 tty3       0.0
 2279 root     /sbin/getty 38400 tty4       0.0
 2280 root     /sbin/getty 38400 tty5       0.0
 2281 root     /sbin/getty 38400 tty6       0.0
13990 root     -bash                        0.0
20478 root     /sbin/getty 38400 console    0.0
20479 root     /sbin/getty 38400 tty1 linu  0.0
20480 root     /sbin/getty 38400 tty2 linu  0.0
20481 root     /sbin/getty 38400 tty3 linu  0.0
20482 root     /sbin/getty 38400 tty4 linu  0.0
24167 root     -bash                        0.0
31031 root     -bash                        0.0
19067 root     init [3]                     0.0
 2132 root     -bash                        0.0
 4549 root     -bash                        0.0
    1 root     init [2]                     0.0
 2508 root     tmux a                       0.0
  503 root     init [3]                     0.0
 4652 root     -bash                        0.0
 7923 root     -bash                        0.0
 2130 root     sshd: root@pts/5             0.0
 1824 root     ssh io                       0.0
 2140 root     /usr/sbin/cron               0.0
  504 root     udevd --daemon               0.0
  505 root     udevd --daemon               0.0
 1826 root     sshd: root@pts/0             0.0
 4544 root     sshd: root@pts/0             0.0
  381 root     udevd --daemon               0.0
16820 root     /usr/sbin/vnstatd -d         0.0
14381 root     /usr/sbin/sshd               0.0
 2224 101      /usr/bin/dbus-daemon --syst  0.0
 8182 ntp      /usr/sbin/ntpd -p /var/run/  0.0
 2497 nst      bash                         0.0
 6459 root     -bash                        0.0
 2382 root     /usr/sbin/console-kit-daemo  0.0
 2472 root     tmux                         0.0
 3074 root     ps -eo pid,user,args,pmem -  0.0
17115 root     /usr/sbin/rsyslogd -c5       0.0
 6149 root     htop                         0.0
 3075 root     view -                       0.1
  911 root     munin-node                   0.1
 2231 snmp     /usr/sbin/snmpd -Lsd -Lf /d  0.1
13988 root     tmux                         0.1
26168 root     -bash                        0.1
27332 root     -bash                        0.1
  628 root     -bash                        0.1
    
por n.st 06.08.2014 / 20:23

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