Since kernel 3.* Linux has introduced a lot of new metrics which can be useful to have them:
MemTotal: 8004768 kB MemFree: 274832 kB MemAvailable: 6684344 kB Buffers: 356 kB Cached: 674384 kB SwapCached: 0 kB Active: 774988 kB Inactive: 361688 kB Active(anon): 591332 kB Inactive(anon): 324776 kB Active(file): 183656 kB Inactive(file): 36912 kB Unevictable: 0 kB Mlocked: 0 kB SwapTotal: 0 kB SwapFree: 0 kB Dirty: 328 kB Writeback: 0 kB AnonPages: 461504 kB Mapped: 102040 kB Shmem: 454320 kB Slab: 6485736 kB SReclaimable: 6442348 kB SUnreclaim: 43388 kB KernelStack: 6544 kB PageTables: 13156 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 4002384 kB Committed_AS: 2593920 kB VmallocTotal: 34359738367 kB VmallocUsed: 168244 kB VmallocChunk: 34359561240 kB HardwareCorrupted: 0 kB AnonHugePages: 204800 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 71552 kB DirectMap2M: 8316928 kB DirectMap1G: 1048576 kB