Fiber.yield() very slow

[simendsjo]

Ref: http://forum.rejectedsoftware.com/groups/rejectedsoftware.vibed/thread/4515/

I don't know any of druntime or vibe internals, so I have no idea how I can find out if this is expected.

I've located the slow code to be libevent2tcp.d -> leastSize -> mctx.core.yieldForEvent() -> Fiber.yield()

[MartinNowak]

Calling Fibers is pretty fast, around 60ns per call on my machine.
It does trash the return stack of the CPU so there are some mispredictions.

import core.thread, std.datetime, std.stdio;

void main()
{
    scope fib = new Fiber({for (;;) Fiber.yield(); });
    auto sw = StopWatch(AutoStart.yes);
    foreach (i; 0 .. 1_000_000)
        fib.call();
    sw.stop();
    writeln(sw.peek.usecs);
}

[s-ludwig]

This seems to be an instance of #338. Can you confirm that it runs fast again on the latest beta?

[s-ludwig]

Closing until confirmed.