You can see exactly how much memory you have available by looking at /proc/user_beancounters
Your burst memory is called 'privvmpages' and is measured in 4k blocks, 'barrier' is the max you can use right now.
The oomguarpages is your guaranteed memory, in 4k blocks. The barrier is the max you can allocate when the system is all out of extra burst memory (should never happen, we under utilize our hardware to keep it speedy).
The system will only report guaranteed memory for safety, its not recommended you use burst for services. The free command will show you how much 'safe' guaranteed memory you have left.
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