正确计算linux系统内存使用率

[root@dvrdvs bin] # free
              total         used         free       shared      buffers
  Mem:        37820        37316          504            0          704
 Swap:            0            0            0
Total:        37820        37316          504
[root@dvrdvs bin] # cat /proc/meminfo 
MemTotal:          37820 kB
MemFree:             500 kB
Buffers:             704 kB
Cached:            12512 kB
SwapCached:            0 kB
Active:            11516 kB
Inactive:          11176 kB
Active(anon):       9708 kB
Inactive(anon):     8160 kB
Active(file):       1808 kB
Inactive(file):     3016 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:          9500 kB
Mapped:             4452 kB
Shmem:              8392 kB
Slab:               6432 kB
SReclaimable:        600 kB
SUnreclaim:         5832 kB
KernelStack:         592 kB
PageTables:          196 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:       18908 kB
Committed_AS:      88428 kB
VmallocTotal:     966656 kB
VmallocUsed:       20720 kB
VmallocChunk:     918896 kB
[root@dvrdvs bin] #