RAM 사용량이 증가하지 않습니까? (무료 + 중고 <합계)

최근에 /proc/meminfo 및 /proc/<pid>에서 읽는 모니터링 스크립트에서 이상한 판독값이 표시되고 수백 MB가 누락된 것 같습니다. htop은 동일한 차이점을 보여줍니다.

CPU: 36.9% sys:  7.6% low:  0.0%                        Tasks: 123; 1 running
Mem:1750M used:1568M buffers:20M cache:87M              Load average: 0.90 1.33 1.33 
Swp:1787M used:184M                                     Uptime: 1 day, 00:28:22
  PID USER      PRI  NI  VIRT   RES   SHR S CPU% MEM%   TIME+  Command
 3455 rena       20   0 1221M  312M 20464 S 14.0 17.8  1h20:26 /usr/lib/firefox/firefox
 1428 root       20   0  327M  100M  6236 S  7.0  5.7  1h28:52 /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nol
14012 rena       20   0  630M 26400  5264 S  0.0  1.5  0:14.20 /usr/bin/python /usr/bin/sonata --toggle
 2562 rena       20   0  914M 21100 10904 S  0.0  1.2  3:59.50 xfce4-terminal --role "Terminal" --hide-menubar -
 2492 rena       20   0  379M 20528  3312 S  0.0  1.1  0:03.53 pcmanfm --desktop --profile lubuntu

사용된 메모리는 1568M이지만 처음 5개 프로세스는 그 근처에서는 사용하지 않습니다: 312+100+26+21+20+20(버퍼) + 87(캐시) = 586M. 그럼 982M은 어딘가에서 사라졌나요?

운영 체제는 Lubuntu 12.04 AMD64입니다.

콘텐츠 /proc/meminfo:

MemTotal:        1792540 kB
MemFree:           67824 kB
Buffers:           17084 kB
Cached:           109624 kB
SwapCached:        69600 kB
Active:           436880 kB
Inactive:         245756 kB
Active(anon):     402348 kB
Inactive(anon):   169616 kB
Active(file):      34532 kB
Inactive(file):    76140 kB
Unevictable:       13456 kB
Mlocked:           13456 kB
SwapTotal:       1830908 kB
SwapFree:        1632380 kB
Dirty:                40 kB
Writeback:             0 kB
AnonPages:        515492 kB
Mapped:            46852 kB
Shmem:              3308 kB
Slab:             875752 kB
SReclaimable:      19108 kB
SUnreclaim:       856644 kB
KernelStack:        2688 kB
PageTables:        19468 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     2727176 kB
Committed_AS:    1741500 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      285612 kB
VmallocChunk:   34359436336 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:     1551232 kB
DirectMap2M:      282624 kB

보드 헤드(크기별):

 Active / Total Objects (% used)    : 1859056 / 1873931 (99.2%)
 Active / Total Slabs (% used)      : 115960 / 115960 (100.0%)
 Active / Total Caches (% used)     : 76 / 108 (70.4%)
 Active / Total Size (% used)       : 906258.20K / 909988.65K (99.6%)
 Minimum / Average / Maximum Object : 0.01K / 0.49K / 8.00K

  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME                   
1640475 1640475 100%    0.53K 109365       15    874920K idr_layer_cache
  4941   4628  93%    0.86K    549        9      4392K ext4_inode_cache
 19068  13243  69%    0.19K    908       21      3632K dentry
  6034   5325  88%    0.55K    431       14      3448K inode_cache
 20272  20272 100%    0.14K    724       28      2896K sysfs_dir_cache