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, 2 insertions, 2 deletions

diff --git a/src/zenstore/cache/structuredcachestore.cpp b/src/zenstore/cache/structuredcachestore.cpp
index da6acbde4..07e72ebb5 100644
--- a/src/zenstore/cache/structuredcachestore.cpp
+++ b/src/zenstore/cache/structuredcachestore.cpp
@@ -1582,7 +1582,7 @@ TEST_CASE("cachestore.threadedinsert")	// * doctest::skip(true))
 
 		CreateDirectories(TempDir.Path());
 
-		WorkerThreadPool  ThreadPool(Max(std::thread::hardware_concurrency(), 8u));
+		WorkerThreadPool  ThreadPool(Max(GetHardwareConcurrency(), 8u));
 		GcManager		  Gc;
 		auto			  JobQueue = MakeJobQueue(1, "testqueue");
 		ZenCacheNamespace Zcs(Gc, *JobQueue, TempDir.Path(), {});
@@ -2257,7 +2257,7 @@ TEST_CASE("cachestore.newgc.basics")
 	std::vector<IoHash> CacheRecords;
 	std::vector<IoHash> UnstructuredCacheValues;
 
-	WorkerThreadPool WorkerPool(Max(std::thread::hardware_concurrency() - 1u, 2u));
+	WorkerThreadPool WorkerPool(Max(GetHardwareConcurrency() - 1u, 2u));
 
 	const auto TearDrinkerBucket = "teardrinker"sv;
 	{