What is the cost of a function call?

Question

Compared to

• Simple memory access
• Disk access
• Memory access on another computer(on the same network)
• Disk access on another computer

Answer 1

relative timings (shouldn't be off by more than a factor of 100 ;-)

• memory-access in cache = 1
• function call/return in cache = 2
• memory-access out of cache = 10 .. 300
• disk access = 1000 .. 1e8 (amortized depends upon the number of bytes transferred)
  • depending mostly upon seek times
  • the transfer itself can be pretty fast
  • involves at least a few thousand ops, since the user/system threshold must be crossed at least twice; an I/O request must be scheduled, the result must be written back; possibly buffers are allocated...
• network calls = 1000 .. 1e9 (amortized depends upon the number of bytes transferred)
  • same argument as with disk i/o
  • the raw transfer speed can be quite high, but some process on the other computer must do the actual work