1 flush thread below 16G, and 2 above.

2 files changed, 9 insertions, 13 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 ee18eceb719..2de06e2053a 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
@@ -18,7 +18,6 @@ public class NodeResourcesTuning implements ProtonConfig.Producer {
     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 = 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;
@@ -94,13 +93,12 @@ public class NodeResourcesTuning implements ProtonConfig.Producer {
     }
 
     private void tuneFlushConcurrentThreads(ProtonConfig.Flush.Builder builder) {
+        int max_concurrent = 2; // TODO bring slowly up towards 4
         if (usableMemoryGb() < MIN_MEMORY_PER_FLUSH_THREAD_GB) {
-            builder.maxconcurrent(1);
+            max_concurrent = 1;
         }
-        double min_concurrent_mem = usableMemoryGb() / (2*MIN_MEMORY_PER_FLUSH_THREAD_GB);
-        double min_concurrent_cpu = resources.vcpu() * MAX_FLUSH_THREAD_RATIO;
-        builder.maxconcurrent(Math.min(builder.build().maxconcurrent(),
-                (int)Math.ceil(Math.max(min_concurrent_mem, min_concurrent_cpu))));
+        double min_concurrent_mem = usableMemoryGb() / MIN_MEMORY_PER_FLUSH_THREAD_GB;
+        builder.maxconcurrent(Math.min(max_concurrent, (int)Math.ceil(min_concurrent_mem)));
     }
 
     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 9fe38512fc0..d344be3da9a 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
@@ -182,14 +182,12 @@ public class NodeResourcesTuningTest {
     }
     @Test
     public void require_that_concurrent_flush_threads_is_1_with_low_memory() {
-        assertEquals(2, fromMemAndCpu(17, 9).flush().maxconcurrent());
-        assertEquals(2, fromMemAndCpu(17, 64).flush().maxconcurrent()); // still capped by max
-        assertEquals(2, fromMemAndCpu(65, 8).flush().maxconcurrent()); // still capped by max
-        assertEquals(2, fromMemAndCpu(33, 8).flush().maxconcurrent());
-        assertEquals(1, fromMemAndCpu(31, 8).flush().maxconcurrent());
-        assertEquals(1, fromMemAndCpu(15, 8).flush().maxconcurrent());
-        assertEquals(1, fromMemAndCpu(17, 8).flush().maxconcurrent());
+        assertEquals(1, fromMemAndCpu(1, 8).flush().maxconcurrent());
         assertEquals(1, fromMemAndCpu(15, 8).flush().maxconcurrent());
+        assertEquals(1, fromMemAndCpu(16, 8).flush().maxconcurrent());
+        assertEquals(2, fromMemAndCpu(17, 8).flush().maxconcurrent());
+        assertEquals(2, fromMemAndCpu(65, 8).flush().maxconcurrent()); // still capped by max
+        assertEquals(2, fromMemAndCpu(65, 65).flush().maxconcurrent()); // still capped by max
     }
 
     private static void assertDocumentStoreMaxFileSize(long expFileSizeBytes, int wantedMemoryGb) {