vmstat: fix cache info #389
Description
Our vmstat cache output is still slightly different from GNU.
Example of output of vmstat (uutils, GNU) and `/proc/meminfo`
$ cargo run -q vmstat && vmstat && cat /proc/meminfo
procs -----------memory---------- ---swap-- -----io---- -system-- -------cpu-------
r b swpd free buff cache si so bi bo in cs us sy id wa st gu
1 0 0 14404020 544 9217476 0 0 656 867 2936 9434 3 1 96 0 0 0
procs -----------memory---------- ---swap-- -----io---- -system-- -------cpu-------
r b swpd free buff cache si so bi bo in cs us sy id wa st gu
0 0 0 14404020 544 9373728 0 0 655 867 2936 5 3 1 96 0 0 0
MemTotal: 32582172 kB
MemFree: 14404020 kB
MemAvailable: 21731464 kB
Buffers: 544 kB
Cached: 9217476 kB
SwapCached: 0 kB
Active: 2990452 kB
Inactive: 13004280 kB
Active(anon): 7464 kB
Inactive(anon): 8366504 kB
Active(file): 2982988 kB
Inactive(file): 4637776 kB
Unevictable: 1466640 kB
Mlocked: 32 kB
SwapTotal: 23437308 kB
SwapFree: 23437308 kB
Zswap: 0 kB
Zswapped: 0 kB
Dirty: 1268 kB
Writeback: 0 kB
AnonPages: 7691144 kB
Mapped: 1980076 kB
Shmem: 1597256 kB
KReclaimable: 156252 kB
Slab: 335844 kB
SReclaimable: 156252 kB
SUnreclaim: 179592 kB
KernelStack: 29208 kB
PageTables: 74808 kB
SecPageTables: 0 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 39728392 kB
Committed_AS: 31735304 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 77688 kB
VmallocChunk: 0 kB
Percpu: 12352 kB
HardwareCorrupted: 0 kB
AnonHugePages: 1941504 kB
ShmemHugePages: 1257472 kB
ShmemPmdMapped: 0 kB
FileHugePages: 0 kB
FilePmdMapped: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
Hugetlb: 0 kB
DirectMap4k: 533760 kB
DirectMap2M: 21204992 kB
DirectMap1G: 11534336 kB