Index: /trunk/src/VBox/Devices/Storage/DevAHCI.cpp
===================================================================
--- /trunk/src/VBox/Devices/Storage/DevAHCI.cpp	(revision 30381)
+++ /trunk/src/VBox/Devices/Storage/DevAHCI.cpp	(revision 30382)
@@ -4940,6 +4940,9 @@
 #endif
 
-        if (!cOutstandingTasks)
-            ahciSendSDBFis(pAhciPort, 0, true);
+        /* Always raise an interrupt after task completion; delaying
+         * this (interrupt coalescing) increases latency and has a significant
+         * impact on performance (see #5071)
+         */
+        ahciSendSDBFis(pAhciPort, 0, true);
     }
     else