Limit number of attribute threads to reduce thread ping pong

2 files changed, 2 insertions, 1 deletions

diff --git a/searchcore/src/tests/proton/documentdb/threading_service_config/threading_service_config_test.cpp b/searchcore/src/tests/proton/documentdb/threading_service_config/threading_service_config_test.cpp
index 340619f09bd..20ec28929a1 100644
--- a/searchcore/src/tests/proton/documentdb/threading_service_config/threading_service_config_test.cpp
+++ b/searchcore/src/tests/proton/documentdb/threading_service_config/threading_service_config_test.cpp
@@ -42,6 +42,7 @@ TEST_F("require that indexing threads are set based on cpu cores and feeding con
     TEST_DO(f.assertIndexingThreads(3, 18));
     TEST_DO(f.assertIndexingThreads(4, 19));
     TEST_DO(f.assertIndexingThreads(4, 24));
+    TEST_DO(f.assertIndexingThreads(4, 64));
 }
 
 TEST_F("require that indexing threads is always >= 1", Fixture(0))
diff --git a/searchcore/src/vespa/searchcore/proton/server/threading_service_config.cpp b/searchcore/src/vespa/searchcore/proton/server/threading_service_config.cpp
index 8f1c3560e9b..07fb8fa102d 100644
--- a/searchcore/src/vespa/searchcore/proton/server/threading_service_config.cpp
+++ b/searchcore/src/vespa/searchcore/proton/server/threading_service_config.cpp
@@ -22,7 +22,7 @@ namespace {
 uint32_t
 calculateIndexingThreads(uint32_t cfgIndexingThreads, double concurrency, const HwInfo::Cpu &cpuInfo)
 {
-    double scaledCores = cpuInfo.cores() * concurrency;
+    double scaledCores = std::min(12.0, cpuInfo.cores() * concurrency);
     uint32_t indexingThreads = std::max((uint32_t)std::ceil(scaledCores / 3), cfgIndexingThreads);
     return std::max(indexingThreads, 1u);
 }