[CentOS] mariadb server memory usage

[marcos valentine]

Disk cache is not recommended for databases servers.

 it'll  slow down the performance. More ram equals more performance.

This link help me understand memory usage on linux.

https://www.linuxatemyram.com/

Basically you need yo worry about

free memory is close to 0
used memory is close to total
available memory (or "free + buffers/cache") has enough room (let's say,
20%+ of total)
swap used does not change
Warning signs of a genuine low memory situation that you may want to look
into:

available memory (or "free + buffers/cache") is close to zero
swap used increases or fluctuates
dmesg | grep oom-killer shows the OutOfMemory-killer at work


You can monitory swap with "vmsat 1"

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2017-11-04 12:05 GMT-02:00 hw <hw at gc-24.de>:

>
> Hi,
>
> is this ok for a database server, or do I need to turn the memory allowance
> down?  The machine has 48GB and mariadb is allowed about 40. The
> machine is a dedicated database server.
>
> Mysql seems to go up to what top says is virtually allocated under some
> circumstances; I don´t know what mariadb does.  I don´t want anything
> get killed because memory runs out.  Swap should prevent that anyway,
> but perhaps I went a bit higher than I should?
>
> Usual advice is to use 80%, and there are probably reasons for that.
> Perhaps it´s better to allow for more disk cache?
>
>
> KiB Mem : 49449424 total,   291772 free, 45891836 used,  3265816 buff/cache
> KiB Swap: 16777212 total, 16742928 free,    34284 used.  2985816 avail Mem
>
>   PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
>  4138 mysql     20   0 48.908g 0.042t  14064 S   0.0 91.8 111:23.17 mysqld
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