Add clarifying comments

2 files changed, 7 insertions, 3 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 20ec28929a1..37ac5f0d65c 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
@@ -1,12 +1,13 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-#include <vespa/log/log.h>
-LOG_SETUP("threading_service_config_test");
 
 #include <vespa/searchcore/config/config-proton.h>
 #include <vespa/searchcore/proton/common/hw_info.h>
 #include <vespa/searchcore/proton/server/threading_service_config.h>
 #include <vespa/vespalib/testkit/testapp.h>
 
+#include <vespa/log/log.h>
+LOG_SETUP("threading_service_config_test");
+
 using namespace proton;
 using ProtonConfig = vespa::config::search::core::ProtonConfig;
 using ProtonConfigBuilder = vespa::config::search::core::ProtonConfigBuilder;
@@ -42,7 +43,7 @@ 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_DO(f.assertIndexingThreads(4, 64)); // Ensure it is capped at 4
 }
 
 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 07fb8fa102d..55aa1a20ef6 100644
--- a/searchcore/src/vespa/searchcore/proton/server/threading_service_config.cpp
+++ b/searchcore/src/vespa/searchcore/proton/server/threading_service_config.cpp
@@ -22,6 +22,9 @@ namespace {
 uint32_t
 calculateIndexingThreads(uint32_t cfgIndexingThreads, double concurrency, const HwInfo::Cpu &cpuInfo)
 {
+    // We are capping at 12 threads to reduce cost of waking up threads
+    // to achieve a better throughput.
+    // TODO: Fix this in a simpler/better way.
     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);