> It clearly isn't. There is definitely work involved for the CPU also when > doing mmap. It is just that you move it from context switching and small I/O > buffer copying to memory management.
*All* memory access a process does is subject to the rules of the memory management unit of the CPU, so that cost is not specific to mmap():ed files (once a given page is in core that is). (But again, I'm not arguing the point in Cassandra's case; just generally.) -- / Peter Schuller (@scode on twitter)
