`vmstat`: fix cache info

[Bluemangoo]

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

[Franklin-Qi]

I will work on it.

[Franklin-Qi]

@Krysztal112233 In my Ubuntu 25.10 environment, the free buff cache information is slightly different from GNU. Our alignment standard is based on procps from GNU or /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 1091117 747773 6065796  0    0   272   209 2650 2957  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
 1  0      0 1117304 765720 6929420    0    0   271   209 2650    3  3  1 96  0  0  0
MemTotal:       15602488 kB
MemFree:         1117304 kB
MemAvailable:    7721012 kB
Buffers:          765720 kB
Cached:          6211376 kB
SwapCached:            0 kB
Active:          8716544 kB
Inactive:        3808436 kB
Active(anon):    6090288 kB
Inactive(anon):   209064 kB
Active(file):    2626256 kB
Inactive(file):  3599372 kB
Unevictable:      522144 kB
Mlocked:             200 kB
SwapTotal:       4194300 kB
SwapFree:        4194300 kB
Zswap:                 0 kB
Zswapped:              0 kB
Dirty:              1700 kB
Writeback:             0 kB
AnonPages:       6070028 kB
Mapped:          1644992 kB
Shmem:            751860 kB
KReclaimable:     718044 kB
Slab:            1094512 kB
SReclaimable:     718044 kB
SUnreclaim:       376468 kB
KernelStack:       23920 kB
PageTables:        91620 kB
SecPageTables:      2992 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    11995544 kB
Committed_AS:   30822500 kB
VmallocTotal:   34359738367 kB
VmallocUsed:       69068 kB
VmallocChunk:          0 kB
Percpu:             9568 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        0 kB
FileHugePages:    112640 kB
FilePmdMapped:     22528 kB
CmaTotal:              0 kB
CmaFree:               0 kB
Unaccepted:            0 kB
Balloon:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:               0 kB
DirectMap4k:      236296 kB
DirectMap2M:     6854656 kB
DirectMap1G:     9437184 kB

[Bluemangoo]

I wonder where GNU get its data. Anyway, do it if we can align with GNU.

[Bluemangoo]

Uh, I found the issue. 1091117 * 1.024 = 1,117,303.8 ≈ 1117304. I think we can check whether GNU changes its default unit (KB or KiB)