Merge pull request #24875 from vespa-engine/balder/reduce-number-of-flush-threads

- If less than 16G memory only use single flush thread.

2 files changed, 11 insertions, 3 deletions

diff --git a/config-model/src/main/java/com/yahoo/vespa/model/search/NodeResourcesTuning.java b/config-model/src/main/java/com/yahoo/vespa/model/search/NodeResourcesTuning.java
index bc5de959f3f..0cf361c10dd 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/search/NodeResourcesTuning.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/search/NodeResourcesTuning.java
@@ -17,7 +17,8 @@ public class NodeResourcesTuning implements ProtonConfig.Producer {
     private final static double SUMMARY_FILE_SIZE_AS_FRACTION_OF_MEMORY = 0.02;
     private final static double SUMMARY_CACHE_SIZE_AS_FRACTION_OF_MEMORY = 0.04;
     private final static double MEMORY_GAIN_AS_FRACTION_OF_MEMORY = 0.08;
-    private final static double MIN_MEMORY_PER_FLUSH_THREAD_GB = 12.0;
+    private final static double MIN_MEMORY_PER_FLUSH_THREAD_GB = 16.0;
+    private final static double MAX_FLUSH_THREAD_RATIO = 1.0/8;
     private final static double TLS_SIZE_FRACTION = 0.02;
     final static long MB = 1024 * 1024;
     public final static long GB = MB * 1024;
@@ -96,6 +97,8 @@ public class NodeResourcesTuning implements ProtonConfig.Producer {
         if (usableMemoryGb() < MIN_MEMORY_PER_FLUSH_THREAD_GB) {
             builder.maxconcurrent(1);
         }
+        builder.maxconcurrent(Math.min(builder.build().maxconcurrent(),
+                                       Math.max(1, (int)Math.ceil(resources.vcpu()*MAX_FLUSH_THREAD_RATIO))));
     }
 
     private void tuneFlushStrategyTlsSize(ProtonConfig.Flush.Memory.Builder builder) {
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/search/NodeResourcesTuningTest.java b/config-model/src/test/java/com/yahoo/vespa/model/search/NodeResourcesTuningTest.java
index 861482ab70c..d0fa205237e 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/search/NodeResourcesTuningTest.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/search/NodeResourcesTuningTest.java
@@ -168,10 +168,15 @@ public class NodeResourcesTuningTest {
         assertSharedDisk(true, true);
     }
 
+    private static ProtonConfig fromMemAndCpu(int gb, int vcpu) {
+        return getConfig(new FlavorsConfig.Flavor.Builder().minMainMemoryAvailableGb(gb).minCpuCores(vcpu));
+    }
     @Test
     public void require_that_concurrent_flush_threads_is_1_with_low_memory() {
-        assertEquals(2, configFromMemorySetting(13, 0).flush().maxconcurrent());
-        assertEquals(1, configFromMemorySetting(11, 0).flush().maxconcurrent());
+        assertEquals(2, fromMemAndCpu(17, 9).flush().maxconcurrent());
+        assertEquals(1, fromMemAndCpu(15, 8).flush().maxconcurrent());
+        assertEquals(1, fromMemAndCpu(17, 8).flush().maxconcurrent());
+        assertEquals(1, fromMemAndCpu(15, 8).flush().maxconcurrent());
     }
 
     private static void assertDocumentStoreMaxFileSize(long expFileSizeBytes, int wantedMemoryGb) {