Are volatile variable 'reads' as fast as normal reads?

Question

I know that writing to a volatile variable flushes it from the memory of all the cpus, however I want to know if reads to a volatile variable are as fast as nor

Answer 1

Volatile reads cannot be as quick, especially on multi-core CPUs (but also only single-core). The executing core has to fetch from the actual memory address to make sure it gets the current value - the variable indeed cannot be cached.

As opposed to one other answer here, volatile variables are not used just for device drivers! They are sometimes essential for writing high performance multi-threaded code!