dsimcha Wrote:
> == Quote from Steven Schveighoffer (schvei...@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
My code does do considerable array appending, and I see exactly the same issue
as dsimcha points out above. I would expect it is GC related, but why for
multiple cores only, I cannot fathom.
Thanks for the repro, dsimcha! My code snippet would not have been as
straight-forward.
