Merge pull request #1973 from magento-performance/MAGETWO-85904-2.1

[Performance] Stabilize PAT tideways metrics [2.1-develop]

Author: vzabaznov

app/code/Magento/Security/Model/AdminSessionsManager.php

@@ -328,7 +328,7 @@ private function getIntervalBetweenConsecutiveProlongs()
         return (float) max(
             1,
             min(
-                log((float)$this->securityConfig->getAdminSessionLifetime()),
+                4 * log((float)$this->securityConfig->getAdminSessionLifetime()),
                 $this->maxIntervalBetweenConsecutiveProlongs
             )
         );

dev/tests/integration/testsuite/Magento/Security/Model/Plugin/AuthSessionTest.php

@@ -132,7 +132,7 @@ public function testProcessProlong()
             \Magento\TestFramework\Bootstrap::ADMIN_PASSWORD
         );
         $sessionId = $this->authSession->getSessionId();
-        $prolongsDiff = log($this->securityConfig->getAdminSessionLifetime()) + 2; // X from comment above
+        $prolongsDiff = 4 * log($this->securityConfig->getAdminSessionLifetime()) + 2; // X from comment above
         $dateInPast = $this->dateTime->formatDate($this->authSession->getUpdatedAt() - $prolongsDiff);
         $this->adminSessionsManager->getCurrentSession()
             ->setData(