diff --git a/src/DrupalCI/Build/Environment/Environment.php b/src/DrupalCI/Build/Environment/Environment.php
index d2e6cfc847c9a0c799a2c442eaba72db2f645a91..386bfd4b37566f6dd7edd3ecf539c71e89b8c5ef 100644
--- a/src/DrupalCI/Build/Environment/Environment.php
+++ b/src/DrupalCI/Build/Environment/Environment.php
@@ -390,4 +390,15 @@ class Environment implements Injectable, EnvironmentInterface {
     return $this->chromeContainer['name'];
   }
 
+  /**
+   * @inheritDoc
+   */
+  public function getHostProcessorCount() {
+    $cpuinfo = file_get_contents('/proc/cpuinfo');
+    preg_match_all('/^processor/m', $cpuinfo, $matches);
+    $numCpus = count($matches[0]);
+    return $numCpus;
+  }
+
+
 }
diff --git a/src/DrupalCI/Build/Environment/EnvironmentInterface.php b/src/DrupalCI/Build/Environment/EnvironmentInterface.php
index 0b3ec96b352818a99e682bc99881b0c6102d0235..9582c83e7bce8a8e3058430b461fff1f65b11a60 100644
--- a/src/DrupalCI/Build/Environment/EnvironmentInterface.php
+++ b/src/DrupalCI/Build/Environment/EnvironmentInterface.php
@@ -62,4 +62,10 @@ interface EnvironmentInterface {
    */
   public function getContainerComposerCacheDir();
 
+  /**
+   * @return int
+   *   The number of processors available in the host environment
+   */
+  public function getHostProcessorCount();
+
 }
diff --git a/src/DrupalCI/Plugin/BuildTask/BuildStep/CodebaseValidate/PhpLint.php b/src/DrupalCI/Plugin/BuildTask/BuildStep/CodebaseValidate/PhpLint.php
index d489ab82d9b217ac7dd5a8c3e10dea21bcae3351..db8ba4e10c3602363a2f90a3cd1b01165341eb7a 100644
--- a/src/DrupalCI/Plugin/BuildTask/BuildStep/CodebaseValidate/PhpLint.php
+++ b/src/DrupalCI/Plugin/BuildTask/BuildStep/CodebaseValidate/PhpLint.php
@@ -60,9 +60,14 @@ class PhpLint extends BuildTaskBase implements BuildStepInterface, BuildTaskInte
     // Make sure
     if (0 < filesize($lintable_files)) {
       $this->saveHostArtifact($lintable_files,'lintable_files.txt');
+
+      if (empty($this->configuration['concurrency'])) {
+        $this->configuration['concurrency'] = $this->environment->getHostProcessorCount();
+      }
+      $concurrency = $this->configuration['concurrency'];
+
       // This should be come Codebase->getLocalDir() or similar
       // Use xargs to concurrently run linting on file.
-      $concurrency = $this->configuration['concurrency'];
       $cmd = "cd " . $this->environment->getExecContainerSourceDir() . " && xargs -P $concurrency -a " . $this->environment->getContainerWorkDir() . '/' . $this->pluginDir . "/lintable_files.txt -I {} php -l '{}'";
       // TODO Throw a BuildException if there are syntax errors.
       $result = $this->environment->executeCommands($cmd);
@@ -79,7 +84,6 @@ class PhpLint extends BuildTaskBase implements BuildStepInterface, BuildTaskInte
    */
   public function getDefaultConfiguration() {
     return [
-      'concurrency' => '4',
     ];
   }
 
diff --git a/src/DrupalCI/Plugin/BuildTask/BuildStep/Testing/Simpletest.php b/src/DrupalCI/Plugin/BuildTask/BuildStep/Testing/Simpletest.php
index e35e4f4fff76a1982d3d50e42102c6d1c3483858..8a8ea0510e232ba378fc129f675304395a07957f 100644
--- a/src/DrupalCI/Plugin/BuildTask/BuildStep/Testing/Simpletest.php
+++ b/src/DrupalCI/Plugin/BuildTask/BuildStep/Testing/Simpletest.php
@@ -217,7 +217,6 @@ class Simpletest extends BuildTaskBase implements BuildStepInterface, BuildTaskI
   public function getDefaultConfiguration() {
     return [
       'testgroups' => '--all',
-      'concurrency' => 4,
       'types' => 'Simpletest,PHPUnit-Unit,PHPUnit-Kernel,PHPUnit-Functional',
       'color' => TRUE,
       'die-on-fail' => FALSE,
@@ -394,6 +393,10 @@ class Simpletest extends BuildTaskBase implements BuildStepInterface, BuildTaskI
     if (empty($config['url'])) {
       $config['url'] = 'http://' . $this->environment->getExecContainer()['name'] . '/subdirectory';
     }
+    if (empty($config['concurrency'])) {
+      $config['concurrency'] = $this->environment->getHostProcessorCount();
+    }
+
     foreach ($config as $key => $value) {
       // Temporary backwards compatibility fix for https://www.drupal.org/node/2906212
       // This will allow us to use older build.yml files. Remove after Feb 2018 or so.