add ability to limit concurrency (#565)

effective concurrency in zenserver can be limited via the `--corelimit=<N>` option on the command line. Any value passed in here will be used instead of the return value from `std::thread::hardware_concurrency()` if it is lower.

* added --corelimit option to zenserver
* made sure thread pools are configured lazily and not during global init
* added log output indicating effective and HW concurrency
* added change log entry
* removed debug logging from ZenEntryPoint::Run()

also removed main thread naming on Linux since it makes the output from `top` and similar tools confusing (it shows `main` instead of `zenserver`)

1 files changed, 21 insertions, 0 deletions

diff --git a/src/zencore/thread.cpp b/src/zencore/thread.cpp
index abf282467..7bd21a229 100644
--- a/src/zencore/thread.cpp
+++ b/src/zencore/thread.cpp
@@ -45,6 +45,27 @@ ZEN_THIRD_PARTY_INCLUDES_END
 
 namespace zen {
 
+static unsigned int LimitConcurrency = 0;
+
+void
+LimitHardwareConcurrency(unsigned int Limit)
+{
+	LimitConcurrency = Limit;
+}
+
+unsigned int
+GetHardwareConcurrency()
+{
+	static unsigned int SysLimit = std::thread::hardware_concurrency();
+
+	if (LimitConcurrency)
+	{
+		return Min(SysLimit, LimitConcurrency);
+	}
+
+	return SysLimit;
+}
+
 #if ZEN_PLATFORM_WINDOWS
 // The information on how to set the thread name comes from
 // a MSDN article: http://msdn2.microsoft.com/en-us/library/xcb2z8hs.aspx