diff --git a/java/server/src/main/java/org/softwareheritage/graph/benchmark/Benchmark.java b/java/server/src/main/java/org/softwareheritage/graph/benchmark/Benchmark.java
--- a/java/server/src/main/java/org/softwareheritage/graph/benchmark/Benchmark.java
+++ b/java/server/src/main/java/org/softwareheritage/graph/benchmark/Benchmark.java
@@ -47,6 +47,8 @@
 
   /** Command line arguments */
   public Args args;
+  /** CSV separator for log file */
+  final String CSV_SEPARATOR = ";";
 
   /**
    * Constructor.
@@ -86,6 +88,22 @@
   }
 
   /**
+   * Creates CSV file for log output.
+   */
+  public void createCSVLogFile() throws IOException {
+    try (Writer csvLog = new BufferedWriter(new FileWriter(args.logFile))) {
+      StringJoiner csvHeader = new StringJoiner(CSV_SEPARATOR);
+      csvHeader.add("use case name")
+          .add("SWH PID")
+          .add("number of edges accessed")
+          .add("traversal timing")
+          .add("pid2node timing")
+          .add("node2pid timing");
+      csvLog.write(csvHeader.toString() + "\n");
+    }
+  }
+
+  /**
    * Times a specific endpoint and outputs individual datapoints along with aggregated statistics.
    *
    * @param useCaseName benchmark use-case name
@@ -102,17 +120,8 @@
     ArrayList<Double> timings = new ArrayList<>();
     ArrayList<Double> timingsNormalized = new ArrayList<>();
 
-    final String CSV_SEPARATOR = ";";
-    try (Writer csvLog = new BufferedWriter(new FileWriter(args.logFile))) {
-      StringJoiner csvHeader = new StringJoiner(CSV_SEPARATOR);
-      csvHeader.add("use case name")
-          .add("SWH PID")
-          .add("number of edges accessed")
-          .add("traversal timing")
-          .add("pid2node timing")
-          .add("node2pid timing");
-      csvLog.write(csvHeader.toString() + "\n");
-
+    final boolean append = true;
+    try (Writer csvLog = new BufferedWriter(new FileWriter(args.logFile, append))) {
       for (long nodeId : nodeIds) {
         SwhPID swhPID = graph.getSwhPID(nodeId);
 
diff --git a/java/server/src/main/java/org/softwareheritage/graph/benchmark/Browsing.java b/java/server/src/main/java/org/softwareheritage/graph/benchmark/Browsing.java
--- a/java/server/src/main/java/org/softwareheritage/graph/benchmark/Browsing.java
+++ b/java/server/src/main/java/org/softwareheritage/graph/benchmark/Browsing.java
@@ -40,6 +40,7 @@
     Endpoint revEndpoint = new Endpoint(graph, "forward", "rev:rev");
 
     System.out.println("Used " + bench.args.nbNodes + " random nodes (results are in seconds):");
+    bench.createCSVLogFile();
     bench.timeEndpoint("ls", graph, dirNodeIds, dirEndpoint::neighbors);
     bench.timeEndpoint("ls -R", graph, dirNodeIds, dirEndpoint::visitPaths);
     bench.timeEndpoint("git log", graph, revNodeIds, revEndpoint::visitNodes);
diff --git a/java/server/src/main/java/org/softwareheritage/graph/benchmark/Provenance.java b/java/server/src/main/java/org/softwareheritage/graph/benchmark/Provenance.java
--- a/java/server/src/main/java/org/softwareheritage/graph/benchmark/Provenance.java
+++ b/java/server/src/main/java/org/softwareheritage/graph/benchmark/Provenance.java
@@ -36,6 +36,7 @@
     Endpoint originProvenanceEndpoint = new Endpoint(graph, "backward", "*");
 
     System.out.println("Used " + bench.args.nbNodes + " random nodes (results are in seconds):");
+    bench.createCSVLogFile();
 
     bench.timeEndpoint(
         "commit provenance (dfs)", graph, nodeIds, commitProvenanceEndpoint::walk, "rev", "dfs");
diff --git a/java/server/src/main/java/org/softwareheritage/graph/benchmark/Vault.java b/java/server/src/main/java/org/softwareheritage/graph/benchmark/Vault.java
--- a/java/server/src/main/java/org/softwareheritage/graph/benchmark/Vault.java
+++ b/java/server/src/main/java/org/softwareheritage/graph/benchmark/Vault.java
@@ -35,6 +35,7 @@
     Endpoint endpoint = new Endpoint(graph, "forward", "*");
 
     System.out.println("Used " + bench.args.nbNodes + " random nodes (results are in seconds):");
+    bench.createCSVLogFile();
     bench.timeEndpoint("git bundle", graph, nodeIds, endpoint::visitNodes);
   }
 }