In Tarantool, are fibers used when the Lua code author wants Tarantool to schedule the execution? Are co-routines (in the Tarantool/LuaJIT process) used when the Lua code author wants to be in control of the execution?
2 Answers
Fiber stack is larger than one of a coroutine. It's mmapp'ed to 64KB, and is at least one OS page (4KB usually). Fiber context switching incurs extra overhead, since it hides/restores registers in addition to hiding/restoring the coroutine. Fiber context switches break JIT in LuaJIT, since LuaJIT is not able to hide/restore traced execution. Unlike coroutines, fibers work well with all non-blocking IO which is built into the application server: whenver a fiber yields implicitly on a IO call, another fiber kicks in. But not another coroutine, of course, you'll have to take care of this yourself if you're using them.
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