Understanding memory in your VPS
Q: How do I know how much Guaranteed RAM my VPS has?
A: The simple answer is to jut type free -m from a command prompt and you will see something like the output below.
total used free shared buffers cached Mem: 512 189 322 0 0 0
The values shown above are in Megabytes so this VPS has 512M of RAM and is using 189M which leaves 322M free.
If you are a bean counter then you can calculate it by typing ‘cat /proc/user_beancounters’ and taking a look at vmguarpages, oomguarpages, and privvmpages in the ‘barrier’ and ‘limit’ columns. If your vmguarpages shows 131072 in the limit column you can do the formula: vmguarpages * 4 /1024 where pages = 4KB and a Megabyte = 1024 KBs.
131072 * 4 /1024 = 512
If you would like to know what your “burstable” RAM just do the same formula but use the privvmpages number in the barrier column. If the barrier for privvmpages is 163840 (i.e. 163840 * 4 / 1024 = 640)
To save you some math some common values are provided below.
32768 = 128M 65536 = 256M 98304 = 384M 131072 = 512M 163840 = 640M 196608 = 768M 262144 = 1024M (1 GB)
We’ll discuss the oomguarpages setting in a later post.