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`)

4 files changed, 11 insertions, 11 deletions

diff --git a/src/zenstore/blockstore.cpp b/src/zenstore/blockstore.cpp
index 0861baaf8..0fee18420 100644
--- a/src/zenstore/blockstore.cpp
+++ b/src/zenstore/blockstore.cpp
@@ -1688,7 +1688,7 @@ TEST_CASE("blockstore.iterate.chunks")
 												.Size		= DefaultIterateSmallChunkWindowSize * 2};
 	BlockStoreLocation BadBlockIndex		 = {.BlockIndex = 0xfffff, .Offset = 1024, .Size = 1024};
 
-	WorkerThreadPool WorkerPool(Max(std::thread::hardware_concurrency() - 1u, 4u));
+	WorkerThreadPool WorkerPool(Max(GetHardwareConcurrency() - 1u, 4u));
 
 	std::vector<BlockStoreLocation> Locations{FirstChunkLocation,
 											  SecondChunkLocation,
@@ -1807,7 +1807,7 @@ TEST_CASE("blockstore.thread.read.write")
 	std::vector<BlockStoreLocation> ChunkLocations;
 	ChunkLocations.resize(ChunkCount);
 
-	WorkerThreadPool WorkerPool(Max(std::thread::hardware_concurrency() - 1u, 8u));
+	WorkerThreadPool WorkerPool(Max(GetHardwareConcurrency() - 1u, 8u));
 	{
 		std::atomic<size_t> WorkCompleted = 0;
 		Latch				L(1);
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;
 	{
diff --git a/src/zenstore/compactcas.cpp b/src/zenstore/compactcas.cpp
index 5cc4dad54..bf843171e 100644
--- a/src/zenstore/compactcas.cpp
+++ b/src/zenstore/compactcas.cpp
@@ -1722,7 +1722,7 @@ TEST_CASE("compactcas.restart")
 {
 	uint64_t ExpectedSize = 0;
 
-	WorkerThreadPool ThreadPool(Max(std::thread::hardware_concurrency() - 1u, 2u), "put");
+	WorkerThreadPool ThreadPool(Max(GetHardwareConcurrency() - 1u, 2u), "put");
 
 	auto GenerateChunks = [&](CasContainerStrategy& Cas, size_t ChunkCount, uint64_t ChunkSize, std::vector<IoHash>& Hashes) {
 		Latch								   WorkLatch(1);
@@ -1959,7 +1959,7 @@ TEST_CASE("compactcas.restart")
 TEST_CASE("compactcas.iteratechunks")
 {
 	std::atomic<size_t> WorkCompleted = 0;
-	WorkerThreadPool	ThreadPool(Max(std::thread::hardware_concurrency() - 1u, 2u), "put");
+	WorkerThreadPool	ThreadPool(Max(GetHardwareConcurrency() - 1u, 2u), "put");
 
 	const uint64_t kChunkSize  = 1048 + 395;
 	const size_t   kChunkCount = 63840;
@@ -2035,7 +2035,7 @@ TEST_CASE("compactcas.iteratechunks")
 			WorkLatch.Wait();
 		}
 
-		WorkerThreadPool BatchWorkerPool(Max(std::thread::hardware_concurrency() - 1u, 2u), "fetch");
+		WorkerThreadPool BatchWorkerPool(Max(GetHardwareConcurrency() - 1u, 2u), "fetch");
 		{
 			std::vector<std::atomic<bool>> FetchedFlags(Hashes.size());
 			std::atomic<uint64_t>		   FetchedSize = 0;
diff --git a/src/zenstore/workspaces.cpp b/src/zenstore/workspaces.cpp
index 4e7bd79a3..c2391588c 100644
--- a/src/zenstore/workspaces.cpp
+++ b/src/zenstore/workspaces.cpp
@@ -1356,7 +1356,7 @@ TEST_CASE("workspaces.scanfolder")
 {
 	using namespace std::literals;
 
-	WorkerThreadPool WorkerPool(std::thread::hardware_concurrency());
+	WorkerThreadPool WorkerPool(GetHardwareConcurrency());
 
 	ScopedTemporaryDirectory TempDir;
 	std::filesystem::path	 RootPath = TempDir.Path();
@@ -1381,7 +1381,7 @@ TEST_CASE("workspace.share.paths")
 {
 	using namespace std::literals;
 
-	WorkerThreadPool WorkerPool(std::thread::hardware_concurrency());
+	WorkerThreadPool WorkerPool(GetHardwareConcurrency());
 
 	ScopedTemporaryDirectory								TempDir;
 	std::filesystem::path									RootPath = TempDir.Path() / "workspace";
@@ -1409,7 +1409,7 @@ TEST_CASE("workspace.share.basic")
 {
 	using namespace std::literals;
 
-	WorkerThreadPool WorkerPool(std::thread::hardware_concurrency());
+	WorkerThreadPool WorkerPool(GetHardwareConcurrency());
 
 	ScopedTemporaryDirectory								TempDir;
 	std::filesystem::path									RootPath = TempDir.Path() / "workspace";
@@ -1503,7 +1503,7 @@ TEST_CASE("workspace.share.alias")
 {
 	using namespace std::literals;
 
-	WorkerThreadPool WorkerPool(std::thread::hardware_concurrency());
+	WorkerThreadPool WorkerPool(GetHardwareConcurrency());
 
 	ScopedTemporaryDirectory								TempDir;
 	std::filesystem::path									RootPath = TempDir.Path() / "workspace";