Linux memory usage …

I’m not sure if this is right, so this could be conjecture, wild coincidence, or just total bullshit.

To find out how much memory you really need in a Linux machine, here’s my guess at how to do it. The OS will use about 90-95% of your memory whether or not you need it or not.

So, I figured, the memory that’s not used by applications is cache, so here’s my reasoning ….
when running “vmstat 5 5” I get:

[email protected]:~$ vmstat 5 5
procs ———–memory———- —swap– —–io—- –system– —-cpu—-
r b swpd free buff cache si so bi bo in cs us sy id wa
0 0 104 40868 97536 211036 0 0 6 20 53 130 3 5 93 0
0 0 104 40868 97540 211032 0 0 0 14 103 184 0 0 100 0
0 0 104 40852 97540 211032 0 0 0 7 103 200 0 0 100 0
0 0 104 40804 97552 211088 0 0 0 47 112 250 0 1 99 0
0 0 104 40748 97556 211084 0 0 0 33 109 213 0 1 99 0

I have ~200mb for cache, which means my applications probably use the rest – 1gb – 200mb = 800mb. I could probably get away with just running on 800mb opposed to 1gb, right?

[email protected]:~$ cat /proc/meminfo
MemTotal: 1035672 kB
MemFree: 40420 kB
Buffers: 97504 kB
Cached: 211068 kB
SwapCached: 12 kB
Active: 770052 kB
Inactive: 134936 kB
HighTotal: 131008 kB
HighFree: 216 kB
LowTotal: 904664 kB
LowFree: 40204 kB
SwapTotal: 867500 kB
SwapFree: 867396 kB
Dirty: 188 kB
Writeback: 0 kB
Mapped: 636228 kB
Slab: 77832 kB
CommitLimit: 1385336 kB
Committed_AS: 1804444 kB
PageTables: 4280 kB
VmallocTotal: 118776 kB
VmallocUsed: 2984 kB
VmallocChunk: 115412 kB

top output:
Mem: 1035672k total, 1001156k used, 34516k free, 89952k buffers
Swap: 867500k total, 104k used, 867396k free, 203864k cached

One thing I don’t want to do is swap.

If I’m wrong, please let me know! Thanks.

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