diff --git a/.github/workflows/run-checks-all.yml b/.github/workflows/run-checks-all.yml
index 53e4a51f668e..fabb8b71f799 100644
--- a/.github/workflows/run-checks-all.yml
+++ b/.github/workflows/run-checks-all.yml
@@ -58,7 +58,7 @@ jobs:
           echo "lucene.tool.ast-grep=ast-grep" >> build-options.local.properties
 
       - name: Run gradle check (without tests)
-        run: ./gradlew check -x test "-Ptask.times=true" --max-workers 2
+        run: ./gradlew check -x test "-Ptask.times=true"
 
 
   # This runs all tests without any other validation checks.
@@ -87,8 +87,20 @@ jobs:
       - name: Configure tools
         uses: ./.github/actions/prepare-for-build
 
+      - name: Speedup MacOS runner
+        if: ${{ runner.os == 'macOS' }}
+        run: |
+          mkdir /tmp/tmpfs
+          sudo mount_tmpfs -o noowners -s 1g /tmp/tmpfs
+          sudo sysctl debug.lowpri_throttle_enabled=0
+          echo "tests.workDir=/tmp/tmpfs/lucene" >> build-options.local.properties
+
       - name: Run gradle tests
-        run: ./gradlew test "-Ptask.times=true" "-Pvalidation.errorprone=false" --max-workers 2
+        run: ./gradlew test "-Ptask.times=true" "-Pvalidation.errorprone=false"
+        env:
+          # Set to the defaults to override the "CI"-based logic that would enable C2
+          # we can't afford C2 on github runners.
+          TEST_JVM_ARGS: "-XX:TieredStopAtLevel=1 -XX:+UseParallelGC -XX:ActiveProcessorCount=1"
 
       - name: List automatically-initialized gradle.properties
         run: cat gradle.properties
diff --git a/build-tools/build-infra/src/main/java/org/apache/lucene/gradle/GradlePropertiesGenerator.java b/build-tools/build-infra/src/main/java/org/apache/lucene/gradle/GradlePropertiesGenerator.java
index 5436afe70f80..b80471371887 100644
--- a/build-tools/build-infra/src/main/java/org/apache/lucene/gradle/GradlePropertiesGenerator.java
+++ b/build-tools/build-infra/src/main/java/org/apache/lucene/gradle/GradlePropertiesGenerator.java
@@ -54,10 +54,10 @@ public void run(Path source, Path destination) throws IOException {
     }
 
     // Approximate a common-sense default for running gradle/tests with parallel
-    // workers: half the count of available cpus but not more than 12.
+    // workers: the count of available cpus but not more than 12.
     var cpus = Runtime.getRuntime().availableProcessors();
-    var maxWorkers = (int) Math.max(1d, Math.min(cpus * 0.5d, 12));
-    var testsJvms = (int) Math.max(1d, Math.min(cpus * 0.5d, 12));
+    var maxWorkers = Math.min(cpus, 12);
+    var testsJvms = Math.min(cpus, 12);
 
     var replacements = Map.of("@MAX_WORKERS@", maxWorkers, "@TEST_JVMS@", testsJvms);
 
diff --git a/build-tools/build-infra/src/main/java/org/apache/lucene/gradle/plugins/java/TestsAndRandomizationPlugin.java b/build-tools/build-infra/src/main/java/org/apache/lucene/gradle/plugins/java/TestsAndRandomizationPlugin.java
index a48ae6c61435..86d240067f4f 100644
--- a/build-tools/build-infra/src/main/java/org/apache/lucene/gradle/plugins/java/TestsAndRandomizationPlugin.java
+++ b/build-tools/build-infra/src/main/java/org/apache/lucene/gradle/plugins/java/TestsAndRandomizationPlugin.java
@@ -186,9 +186,7 @@ public void apply(Project project) {
                 .getProviders()
                 .provider(
                     () -> {
-                      return ((int)
-                          Math.max(
-                              1, Math.min(Runtime.getRuntime().availableProcessors() / 2.0, 4.0)));
+                      return Math.min(12, Runtime.getRuntime().availableProcessors());
                     }));
 
     // GITHUB#13986: Allow easier configuration of the Panama Vectorization provider with newer Java
diff --git a/gradle/template.gradle.properties b/gradle/template.gradle.properties
index 59ae7422b0a0..1e808746e1b5 100644
--- a/gradle/template.gradle.properties
+++ b/gradle/template.gradle.properties
@@ -16,7 +16,7 @@
 ###############
 #
 # Gradle build can run tasks in parallel but by default it consumes all CPU cores which
-# is too optimistic a default for Lucene tests. You can disable the parallelism
+# may be too optimistic a default for Lucene tests. You can disable the parallelism
 # entirely or assign it a 'low' priority with these properties:
 #
 # org.gradle.parallel=[true, false]
@@ -24,7 +24,7 @@
 #
 # The default level of parallelism is computed based on the number of cores on
 # your machine (on the first run of gradle build). By default these are fairly conservative
-# settings (half the number of cores for workers, for example):
+# settings (the number of cores for workers up to a limit of 12, for example):
 #
 # org.gradle.workers.max=[X]
 # tests.jvms=[N <= X]