If there is less than 12G memory, use only single flush thread.

2 files changed, 14 insertions, 0 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 9b9a525ab29..bc5de959f3f 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
@@ -17,6 +17,7 @@ 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 TLS_SIZE_FRACTION = 0.02;
     final static long MB = 1024 * 1024;
     public final static long GB = MB * 1024;
@@ -45,6 +46,7 @@ public class NodeResourcesTuning implements ProtonConfig.Producer {
         tuneDocumentStoreMaxFileSize(builder.summary.log);
         tuneFlushStrategyMemoryLimits(builder.flush.memory);
         tuneFlushStrategyTlsSize(builder.flush.memory);
+        tuneFlushConcurrentThreads(builder.flush);
         tuneSummaryReadIo(builder.summary.read);
         tuneSummaryCache(builder.summary.cache);
         tuneSearchReadIo(builder.search.mmap);
@@ -90,6 +92,12 @@ public class NodeResourcesTuning implements ProtonConfig.Producer {
         builder.each.maxmemory(memoryLimitBytes);
     }
 
+    private void tuneFlushConcurrentThreads(ProtonConfig.Flush.Builder builder) {
+        if (usableMemoryGb() < MIN_MEMORY_PER_FLUSH_THREAD_GB) {
+            builder.maxconcurrent(1);
+        }
+    }
+
     private void tuneFlushStrategyTlsSize(ProtonConfig.Flush.Memory.Builder builder) {
         long tlsSizeBytes = (long) ((resources.diskGb() * TLS_SIZE_FRACTION) * GB);
         tlsSizeBytes = max(2*GB, min(tlsSizeBytes, 100 * GB));
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 fece6ca47e3..861482ab70c 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
@@ -168,6 +168,12 @@ public class NodeResourcesTuningTest {
         assertSharedDisk(true, true);
     }
 
+    @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());
+    }
+
     private static void assertDocumentStoreMaxFileSize(long expFileSizeBytes, int wantedMemoryGb) {
         assertEquals(expFileSizeBytes, configFromMemorySetting(wantedMemoryGb + reservedMemoryGb, 0).summary().log().maxfilesize());
     }