Memory usage monitoring

Hello Zen_Y , 
yes all Memory allocated, but don't care about Other memory utilization, in most cases it's expected behavior by design , have a look in this article https://my.f5.com/manage/s/article/K21932733 

but always monitor and keen on TMM memory, you must have always Free TMM memory, if TMM fully utilized , your BIGIP/VE can't process traffic any more , I believe that this could never happen as there is an Eviction policy applied by default to keep the TMM memory , but in case you find TMM increasing this indication of ( high traffic/ client connections , DoS Attacks or memory leakage ) , so you have to care about it.

Calculate the Total memory used ( TMM + Other memory ) will not be beneficial, because like I said the other memory isn't that important thing to monitor. 
Other memory is used for some internal tasks such as Linux host processing or Kernel , have a look in this article: https://my.f5.com/manage/s/article/K16419 

But again, if you asking that 
Total memory = ( TMM memory + Other memory ) that's right, but I see it has no vital meaning. 

For Example from my VE in lab : 

Kind Regards