MemAvailable higher than expected

$ free -h total used free shared buff/cache available Mem: 7.7Gi 4.5Gi 692Mi 305Mi 2.5Gi 2.6Gi Swap: 2.0Gi 25Mi 2.0Gi How can MemAvailable be this high on my system? When I read [the kernel code](https://github.com/torvalds/linux/commit/34e431b0ae39) , I thought we could approximate MemAvailable with a formula like MemFree + (Buffers + Cached - Shmem)/2 + SReclaimable/2. So I would have guessed MemAvailable would be more like 1.8G. I don't think the 0.8G difference is due to the Reclaimable Slabs part, because I only have 100M of them: $ grep SReclaimable /proc/meminfo SReclaimable: 106492 kB --- $ uname -r 4.20.3-200.fc29.x86_64 $ cat /proc/meminfo MemTotal: 8042592 kB MemFree: 708864 kB MemAvailable: 2740432 kB Buffers: 225472 kB Cached: 2289436 kB SwapCached: 1768 kB Active: 4367844 kB Inactive: 2538636 kB Active(anon): 3443868 kB Inactive(anon): 1265012 kB Active(file): 923976 kB Inactive(file): 1273624 kB Unevictable: 11528 kB Mlocked: 11528 kB SwapTotal: 2097148 kB SwapFree: 2071412 kB Dirty: 80 kB Writeback: 44 kB AnonPages: 4402684 kB Mapped: 554452 kB Shmem: 313044 kB KReclaimable: 106492 kB Slab: 249164 kB SReclaimable: 106492 kB SUnreclaim: 142672 kB KernelStack: 17888 kB PageTables: 37020 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 6118444 kB Committed_AS: 12077056 kB VmallocTotal: 34359738367 kB VmallocUsed: 0 kB VmallocChunk: 0 kB Percpu: 2688 kB HardwareCorrupted: 0 kB AnonHugePages: 2160640 kB ShmemHugePages: 0 kB ShmemPmdMapped: 0 kB CmaTotal: 0 kB CmaFree: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Hugetlb: 0 kB DirectMap4k: 297524 kB DirectMap2M: 7968768 kB DirectMap1G: 1048576 kB