On Sunday, 6 March 2016 at 13:21:41 UTC, Shachar Shemesh wrote:
You have an iret whether you switched or not. Going into the kernel and coming back has that, whether we switched or not. In particular, since you need a system call in order to call "read", "write" and "accept", these are there regardless.
Yes, rule-of-thumb seems to be that regular syscall can be expected to have 200-1000 cycles overhead, on a virtualized setup 2000+ cycles.
But some low level interfaces allow you to submit multiple i/o-ops in a single system call.
