求助，ubuntu16.04 内存识别不完全

$ lsb_release -a
No LSB modules are available.
Distributor ID:Ubuntu
Description:Ubuntu 16.04.1 LTS
Release:16.04
Codename:xenial
$ uname -a
Linux sunbo 4.4.0-57-generic #78-Ubuntu SMP Fri Dec 9 23:50:32 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
系统和内核是这样的……

$ cat /proc/meminfo
MemTotal: 8084700 kB
MemFree: 3655072 kB
MemAvailable: 4971632 kB
Buffers: 249152 kB
Cached: 1440804 kB
SwapCached: 0 kB
Active: 3117692 kB
Inactive: 811524 kB
Active(anon): 2241208 kB
Inactive(anon): 273140 kB
Active(file): 876484 kB
Inactive(file): 538384 kB
Unevictable: 132 kB
Mlocked: 132 kB
SwapTotal: 31998972 kB
SwapFree: 31998972 kB
Dirty: 2212 kB
Writeback: 0 kB
AnonPages: 2239484 kB
Mapped: 717644 kB
Shmem: 275076 kB
Slab: 274212 kB
SReclaimable: 209700 kB
SUnreclaim: 64512 kB
KernelStack: 12480 kB
PageTables: 48764 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 36041320 kB
Committed_AS: 7498304 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 0 kB
VmallocChunk: 0 kB
HardwareCorrupted: 0 kB
AnonHugePages: 1241088 kB
CmaTotal: 0 kB
CmaFree: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 340684 kB
DirectMap2M: 5861376 kB
DirectMap1G: 2097152 kB
看不懂……