Windows multi-threading performance issues on multi-core systems only

[dsimcha]

== Quote from Steven Schveighoffer (schveiguy at yahoo.com)'s article
> Maybe I'm wrong, is there a good test case to prove it is worse on
> multiple cores?
> -Steve

This is a synthetic, extreme corner case benchmark, but I think it hammers home
the point that such problems are at least plausible.  Tested on a Core 2 Quad with
-O -inline -release:

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

void main() {
    writeln("Set affinity, then press enter.");
    readln();

    auto pc = new PerformanceCounter;
    pc.start;

    enum nThreads = 4;
    auto threads = new Thread[nThreads];
    foreach(ref thread; threads) {
        thread = new Thread(&doAppending);
        thread.start();
    }

    foreach(thread; threads) {
        thread.join();
    }

    pc.stop;
    writeln(pc.milliseconds);
}

void doAppending() {
    uint[] arr;
    foreach(i; 0..1_000_000) {
        arr ~= i;
    }
}

Timing with affinity for all 4 CPUs:  28390 milliseconds

Timing with affinity for only 1 CPU:  533 milliseconds