diff --git a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsAdapterBase.java b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsAdapterBase.java
new file mode 100644
index 0000000..ddc7b2d
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsAdapterBase.java
@@ -0,0 +1,30 @@
+// Copyright (c) 2024, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+package com.android.tools.r8.benchmarks;
+
+import com.google.gson.JsonObject;
+import java.util.Collection;
+import java.util.function.IntToLongFunction;
+
+public abstract class BenchmarkResultsAdapterBase {
+
+  void addPropertyIfValueDifferentFromRepresentative(
+      JsonObject resultObject,
+      String propertyName,
+      int iteration,
+      Collection<?> results,
+      IntToLongFunction getter) {
+    if (results.isEmpty()) {
+      return;
+    }
+    long result = getter.applyAsLong(iteration);
+    if (iteration != 0) {
+      long representativeResult = getter.applyAsLong(0);
+      if (result == representativeResult) {
+        return;
+      }
+    }
+    resultObject.addProperty(propertyName, result);
+  }
+}
diff --git a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsCollection.java b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsCollection.java
index 7d006fc..9ca4f81 100644
--- a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsCollection.java
+++ b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsCollection.java
@@ -86,11 +86,13 @@
   }
 
   @Override
-  public void writeResults(Path path) throws IOException {
+  public void writeResults(Path path, BenchmarkResults warmupResults) throws IOException {
     for (Entry<String, BenchmarkResultsSingle> entry : results.entrySet()) {
       String name = entry.getKey();
       BenchmarkResultsSingle result = entry.getValue();
-      result.writeResults(path.resolve(name));
+      BenchmarkResults warmupSubResults =
+          warmupResults != null ? warmupResults.getSubResults(name) : null;
+      result.writeResults(path.resolve(name), warmupSubResults);
     }
   }
 }
diff --git a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsSingle.java b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsSingle.java
index e029bcd..22fbf4a 100644
--- a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsSingle.java
+++ b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsSingle.java
@@ -10,6 +10,7 @@
 import com.android.tools.r8.dex.DexSection;
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
+import com.google.gson.JsonObject;
 import it.unimi.dsi.fastutil.ints.Int2ReferenceMap;
 import it.unimi.dsi.fastutil.longs.LongArrayList;
 import it.unimi.dsi.fastutil.longs.LongList;
@@ -268,14 +269,20 @@
   }
 
   @Override
-  public void writeResults(Path path) throws IOException {
+  public void writeResults(Path path, BenchmarkResults warmupResults) throws IOException {
     try (PrintStream out = new PrintStream(Files.newOutputStream(path))) {
       Gson gson =
           new GsonBuilder()
               .registerTypeAdapter(
                   BenchmarkResultsSingle.class, new BenchmarkResultsSingleAdapter())
+              .registerTypeAdapter(
+                  BenchmarkResultsWarmup.class, new BenchmarkResultsWarmupAdapter())
               .create();
-      out.print(gson.toJson(this));
+      JsonObject json = (JsonObject) gson.toJsonTree(this);
+      if (warmupResults != null) {
+        json.add("warmup", gson.toJsonTree(warmupResults));
+      }
+      out.print(json);
     }
   }
 }
diff --git a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsSingleAdapter.java b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsSingleAdapter.java
index 90a257c..7e62cfc 100644
--- a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsSingleAdapter.java
+++ b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsSingleAdapter.java
@@ -11,10 +11,9 @@
 import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import java.lang.reflect.Type;
-import java.util.Collection;
-import java.util.function.IntToLongFunction;
 
-public class BenchmarkResultsSingleAdapter implements JsonSerializer<BenchmarkResultsSingle> {
+public class BenchmarkResultsSingleAdapter extends BenchmarkResultsAdapterBase
+    implements JsonSerializer<BenchmarkResultsSingle> {
 
   @Override
   public JsonElement serialize(
@@ -43,7 +42,7 @@
       for (int section : DexSection.getConstants()) {
         String sectionName = DexSection.typeName(section);
         String sectionNameUnderscore =
-            CaseFormat.UPPER_CAMEL.to(CaseFormat.UPPER_UNDERSCORE, sectionName);
+            CaseFormat.UPPER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, sectionName);
         addPropertyIfValueDifferentFromRepresentative(
             resultObject,
             "dex_" + sectionNameUnderscore + "_size",
@@ -71,23 +70,4 @@
     benchmarkObject.add("results", resultsArray);
     return benchmarkObject;
   }
-
-  private void addPropertyIfValueDifferentFromRepresentative(
-      JsonObject resultObject,
-      String propertyName,
-      int iteration,
-      Collection<?> results,
-      IntToLongFunction getter) {
-    if (results.isEmpty()) {
-      return;
-    }
-    long result = getter.applyAsLong(iteration);
-    if (iteration != 0) {
-      long representativeResult = getter.applyAsLong(0);
-      if (result == representativeResult) {
-        return;
-      }
-    }
-    resultObject.addProperty(propertyName, result);
-  }
 }
diff --git a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsWarmup.java b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsWarmup.java
index 16084c1..12e4b9a 100644
--- a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsWarmup.java
+++ b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsWarmup.java
@@ -12,6 +12,9 @@
 import it.unimi.dsi.fastutil.longs.LongArrayList;
 import it.unimi.dsi.fastutil.longs.LongList;
 import java.nio.file.Path;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
 
 public class BenchmarkResultsWarmup implements BenchmarkResults {
 
@@ -20,10 +23,19 @@
   private long codeSizeResult = -1;
   private long resourceSizeResult = -1;
 
+  private final Map<String, BenchmarkResultsWarmup> results = new HashMap<>();
+
   public BenchmarkResultsWarmup(String name) {
     this.name = name;
   }
 
+  public BenchmarkResultsWarmup(String name, Map<String, Set<BenchmarkMetric>> benchmarks) {
+    this.name = name;
+    benchmarks.forEach(
+        (benchmarkName, metrics) ->
+            results.put(benchmarkName, new BenchmarkResultsWarmup(benchmarkName)));
+  }
+
   @Override
   public void addRuntimeResult(long result) {
     runtimeResults.add(result);
@@ -84,10 +96,13 @@
     addRuntimeResult(averageRuntimeResult);
   }
 
+  public LongList getRuntimeResults() {
+    return runtimeResults;
+  }
+
   @Override
   public BenchmarkResults getSubResults(String name) {
-    // When running warmups all results are amended to the single warmup result.
-    return this;
+    return results.get(name);
   }
 
   @Override
@@ -95,6 +110,10 @@
     return false;
   }
 
+  public int size() {
+    return runtimeResults.size();
+  }
+
   @Override
   public void printResults(ResultMode mode, boolean failOnCodeSizeDifferences) {
     if (runtimeResults.isEmpty()) {
@@ -108,7 +127,7 @@
   }
 
   @Override
-  public void writeResults(Path path) {
+  public void writeResults(Path path, BenchmarkResults warmupResults) {
     throw new Unimplemented();
   }
 }
diff --git a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsWarmupAdapter.java b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsWarmupAdapter.java
new file mode 100644
index 0000000..19cffef
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkResultsWarmupAdapter.java
@@ -0,0 +1,32 @@
+// Copyright (c) 2024, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+package com.android.tools.r8.benchmarks;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+import java.lang.reflect.Type;
+
+public class BenchmarkResultsWarmupAdapter extends BenchmarkResultsAdapterBase
+    implements JsonSerializer<BenchmarkResultsWarmup> {
+
+  @Override
+  public JsonElement serialize(
+      BenchmarkResultsWarmup result, Type type, JsonSerializationContext jsonSerializationContext) {
+    JsonArray resultsArray = new JsonArray();
+    for (int iteration = 0; iteration < result.size(); iteration++) {
+      JsonObject resultObject = new JsonObject();
+      addPropertyIfValueDifferentFromRepresentative(
+          resultObject,
+          "runtime",
+          iteration,
+          result.getRuntimeResults(),
+          i -> result.getRuntimeResults().getLong(i));
+      resultsArray.add(resultObject);
+    }
+    return resultsArray;
+  }
+}
diff --git a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkRunner.java b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkRunner.java
index 3f1db19..85ae724 100644
--- a/src/test/java/com/android/tools/r8/benchmarks/BenchmarkRunner.java
+++ b/src/test/java/com/android/tools/r8/benchmarks/BenchmarkRunner.java
@@ -53,8 +53,12 @@
   public void run(BenchmarkRunnerFunction fn) throws Exception {
     long warmupTotalTime = 0;
     BenchmarkConfig config = environment.getConfig();
-    BenchmarkResults warmupResults = new BenchmarkResultsWarmup(config.getName());
+    BenchmarkResultsWarmup warmupResults = null;
     if (warmups > 0) {
+      warmupResults =
+          config.isSingleBenchmark()
+              ? new BenchmarkResultsWarmup(config.getName())
+              : new BenchmarkResultsWarmup(config.getName(), config.getSubBenchmarks());
       long start = System.nanoTime();
       for (int i = 0; i < warmups; i++) {
         fn.run(warmupResults);
@@ -84,7 +88,7 @@
     printMetaInfo("benchmark", getBenchmarkIterations(), benchmarkTotalTime);
     results.printResults(resultMode, environment.failOnCodeSizeDifferences());
     if (environment.hasOutputPath()) {
-      results.writeResults(environment.getOutputPath());
+      results.writeResults(environment.getOutputPath(), warmupResults);
     }
     System.out.println();
   }
diff --git a/src/test/testbase/java/com/android/tools/r8/benchmarks/BenchmarkResults.java b/src/test/testbase/java/com/android/tools/r8/benchmarks/BenchmarkResults.java
index 42fb589..92cfd22 100644
--- a/src/test/testbase/java/com/android/tools/r8/benchmarks/BenchmarkResults.java
+++ b/src/test/testbase/java/com/android/tools/r8/benchmarks/BenchmarkResults.java
@@ -40,7 +40,7 @@
 
   void printResults(ResultMode resultMode, boolean failOnCodeSizeDifferences);
 
-  void writeResults(Path path) throws IOException;
+  void writeResults(Path path, BenchmarkResults warmupResults) throws IOException;
 
   static String prettyTime(long nanoTime) {
     return "" + (nanoTime / 1000000) + " ms";