diff --git a/base/PerfOptions.php b/base/PerfOptions.php
index bf22796..2b44034 100644
--- a/base/PerfOptions.php
+++ b/base/PerfOptions.php
@@ -108,6 +108,12 @@ final class PerfOptions {
   public ?string $scriptAfterWarmup;
   public ?string $scriptAfterBenchmark;
 
+
+  // Fine tune for some benchmark options.
+  public ?int $benchmarkConcurrency;
+  public ?string $benchmarkTime;
+  public ?int $benchmarkWarmConcurrency;
+
   public bool $notBenchmarking = false;
 
   private array $args;
@@ -142,6 +148,9 @@ public function __construct(Vector<string> $argv) {
       'profBC',
       'setUpTest:',
       'tearDownTest:',
+      'benchmark-time:',
+      'benchmark-concurrency:',
+      'benchmark-warm-concurrency:',
       'i-am-not-benchmarking',
       'hhvm-extra-arguments:',
       'php-extra-arguments:',
@@ -215,6 +224,11 @@ public function __construct(Vector<string> $argv) {
       $this->forceInnodb = true;
     }
 
+    $this->benchmarkTime = hphp_array_idx($o, 'benchmark-time', null);
+    $this->benchmarkConcurrency = hphp_array_idx($o, 'benchmark-concurrency',
+                                    null);
+    $this->benchmarkWarmConcurrency = hphp_array_idx($o,
+                                        'benchmark-warm-concurrency', null);
     $this->notBenchmarking = array_key_exists('i-am-not-benchmarking', $o);
 
     // If any arguments below here are given, then the "standard
@@ -376,6 +390,37 @@ public function validate() {
       );
     }
 
+    if ($this->benchmarkTime != null) {
+      // [1-9]+[HMS]
+      if (!preg_match("/^[1-9][0-9]*[HMS]{1}$/", $this->benchmarkTime)) {
+        fprintf(STDERR, "*** WARNING ***\n Invalid benchmark time format: %s.
+          Examples of valid format are 2M, 30S, 1H. Using default 1M.\n",
+          $this->benchmarkTime);
+        // Already have a static method who return the default value for siege.
+        $this->benchmarkTime = null;
+      }
+    }
+
+    if ($this->benchmarkWarmConcurrency != null) {
+      if (!preg_match("/^[1-9][0-9]*/", $this->benchmarkWarmConcurrency)) {
+       fprintf(STDERR, "*** WARNING ***\n Invalid benchmark concurrency warmup
+         value: %s. Must be a value greater than 0. Using default 200.\n",
+         $this->benchmarkWarmConcurrency);
+       // Already have a static method who return the default value for siege.
+       $this->benchmarkWarmConcurrency = null;
+      }
+    }
+
+    if ($this->benchmarkConcurrency != null) {
+      if (!preg_match("/^[1-9][0-9]*/", $this->benchmarkConcurrency)) {
+       fprintf(STDERR, "*** WARNING ***\n Invalid benchmark concurrency value:
+         %s. Must be a value greater than 0. Using default 200.\n",
+         $this->benchmarkConcurrency);
+        // Already have a static method who return the default value for siege.
+        $this->benchmarkConcurrency = null;
+      }
+    }
+
     SystemChecks::CheckAll($this);
 
     // Validates that one was defined
diff --git a/base/Siege.php b/base/Siege.php
index 0cc1922..33c1939 100644
--- a/base/Siege.php
+++ b/base/Siege.php
@@ -114,10 +114,15 @@ protected function getArguments(): Vector<string> {
         );
         return $arguments;
       case RequestModes::WARMUP_MULTI:
+        if ($this->options->benchmarkWarmConcurrency != null) {
+          $concurrency = $this->options->benchmarkWarmConcurrency;
+        } else {
+          $concurrency = (string) PerfSettings::BenchmarkConcurrency();
+        }
         $arguments->addAll(
           Vector {
             '-c',
-            (string) PerfSettings::BenchmarkConcurrency(),
+            $concurrency,
             '-t',
             '1M',
             '-f',
@@ -128,10 +133,15 @@ protected function getArguments(): Vector<string> {
         );
         return $arguments;
       case RequestModes::BENCHMARK:
+        if ($this->options->benchmarkConcurrency != null) {
+          $concurrency = $this->options->benchmarkConcurrency;
+        } else {
+          $concurrency = (string) PerfSettings::BenchmarkConcurrency();
+        }
         $arguments->addAll(
           Vector {
             '-c',
-            (string) PerfSettings::BenchmarkConcurrency(),
+            $concurrency,
             '-f',
             $urls_file,
             '--benchmark',
@@ -141,7 +151,11 @@ protected function getArguments(): Vector<string> {
 
         if (!$this->options->noTimeLimit) {
           $arguments->add('-t');
-          $arguments->add(PerfSettings::BenchmarkTime());
+          if ($this->options->benchmarkTime == null) {
+            $arguments->add(PerfSettings::BenchmarkTime());
+          } else {
+            $arguments->add($this->options->benchmarkTime);
+          }
         }
         return $arguments;
       default: