libkorutin

Coroutines are a nice concept, but there are barely any C libraries that could be widely used in production at the moment. Libraries that available have random shortcomings here and there.

This is a small proof-of-concept library to try to avoid common shortcomings:

• It should work on all popular platforms.
• It doesn’t change stack locations (unlike pypy stacklet).
• It doesn’t allocate any memory.

The heavy lifting in libkorutin is done by stack switching code from pypy's stacklet, which seems to be the most complete asm routine library on a market.

TODO:

• Extensive built-in self check suite.
• Basic scheduler.
• Channels.
• Ability to run a coroutine from another coroutine.
• Stack switching for emscripten/js.
• More fallback stack switching solution in case if asm fails.
• Investigate using boost context asm backend.

Backends

• PyPy stacklet switch, asm based, provides stack pointer switch. Fastest backend, but depends on ABI.
• Threads. Slow and doesn't scale (~50 coroutines is ok), but should work if other options fail.
• boost context, TODO.
• ucontext, TODO.
• setjmp, TODO.
• emscripten, TODO.

Platform support

OS	ABI	Switch	Threads
Windows	x86	✓	✓
Windows	x64	✓	✓
Linux	x86	?	?
Linux	x64	?	?
Linux	armv7	?	?
Linux	arm64	?	?
FreeBSD	x86	?	?
FreeBSD	x64	?	?
MacOS	x86	✓	✓
MacOS	x64	✓	✓
iOS	sim32	✓	✓
iOS	sim64	✓	✓
iOS	armv7	?	✓
iOS	arm64	✗	✓
Android	x86	?	?
Android	x64	?	?
Android	armv7	?	?
Android	arm64	?	?
Emscripten	asm.js	✗	✗
Emscripten	wasm	✗	✗

Performance

• Value means switches per second.
• (X) means amount of coroutines yielded/scheduled.

OS	CPU	ABI	Switch (1024)	Switch(16384)	Threads (32)	Threads (64)	Threads (128)
Windows 10 x64	i3770	x86	12337349	10625162	176795	94395	45812
Windows 10 x64	i3770	x64	20897959	9875828	205128	87551	47513
MacOS 10.13.2	i4980hq	x86	11292405	8162099	46093	16470	7181
MacOS 10.13.2	i4980hq	x64	22218395	15899470	46947	16641	7334
iOS 11.2.2	A9	arm64	✗	✗	17764	6353	1930