linux kernel - Entry in /proc/meminfo

Question

I am now study linux. cat /proc/meminfo produces as following. Please tell me the mean of entry "Active(file)/Inactive(file)". I can't find the explanation of these entry. Thanks.

MemTotal:        7736104 kB
MemFree:          166580 kB
Buffers:          604636 kB
Cached:          5965376 kB
SwapCached:            0 kB
Active:          4294464 kB
Inactive:        2319240 kB
Active(anon):      13688 kB
Inactive(anon):    33828 kB
Active(file):    4280776 kB
Inactive(file):  2285412 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:      16777208 kB
SwapFree:       16777208 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:         43772 kB
Mapped:            11056 kB
Shmem:              3792 kB
Slab:             861004 kB
SReclaimable:     818040 kB
SUnreclaim:        42964 kB
KernelStack:        1624 kB
PageTables:         5460 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    20645260 kB
Committed_AS:     124392 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      450644 kB
VmallocChunk:   34359282660 kB
HardwareCorrupted:     0 kB
AnonHugePages:      2048 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:       16384 kB
DirectMap2M:     3880960 kB
DirectMap1G:     4194304 kB

Answer 1

According to the output, result of Active(file) + Inactive(file) + Shmem doesn't equal to that of Cached + Buffer + SwapCached