From f14b9214381d316998b7e6342d24543ff444e4ab Mon Sep 17 00:00:00 2001
From: Leandro Lucarella <llucax@gmail.com>
Date: Wed, 16 Jun 2010 21:07:31 -0300
Subject: [PATCH 1/1] Add multicore contention micro benchmark

---
 micro/multicore.d | 71 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 micro/multicore.d

diff --git a/micro/multicore.d b/micro/multicore.d
new file mode 100644
index 0000000..184fbb9
--- /dev/null
+++ b/micro/multicore.d
@@ -0,0 +1,71 @@
+// Written by David Schima:
+// http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=103563
+//
+// Modified by Leandro Lucarella:
+// * Removed initial "pause"
+// * Removed performance counter
+// * Adapted to D1/Tango
+//
+// Compiled with: -O -inline -release
+//
+// Timing with affinity for all 4 CPUs:  28390 milliseconds
+// Timing with affinity for only 1 CPU:  533 milliseconds
+//
+// More about contention killing multi-core:
+//
+// 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(&doStuff);
+//        thread.start();
+//    }
+//
+//    foreach(thread; threads) {
+//        thread.join();
+//    }
+//
+//    pc.stop;
+//    writeln(pc.milliseconds);
+// }
+//
+// void doStuff() {
+//     foreach(i; 0..1_000_000) {
+//        synchronized {}
+//     }
+// }
+//
+// Timing with affinity for all CPUs:  20772 ms.
+// Timing with affinity for 1 CPU:  156 ms.
+//
+// Post on using spin locks in the GC to avoid contention:
+// http://www.digitalmars.com/d/archives/digitalmars/D/More_on_GC_Spinlocks_80485.html
+
+import tango.core.Thread;
+
+void main() {
+	enum { nThreads = 4 };
+	auto threads = new Thread[nThreads];
+	foreach(ref thread; threads) {
+		thread = new Thread(&doAppending);
+		thread.start();
+	}
+
+	foreach(thread; threads)
+		thread.join();
+}
+
+void doAppending() {
+	uint[] arr;
+	for (size_t i = 0; i < 1_000_000; i++)
+		arr ~= i;
+}
+
-- 
2.43.0