https://bugzilla.mozilla.org/show_bug.cgi?id=815681

diff --git a/xpcom/base/AvailableMemoryTracker.cpp b/xpcom/base/AvailableMemoryTracker.cpp
index 69af67d..ef98fec 100644
--- a/xpcom/base/AvailableMemoryTracker.cpp
+++ b/xpcom/base/AvailableMemoryTracker.cpp
@@ -26,9 +26,7 @@
 #   include <windows.h>
 #endif
 
-#if defined(MOZ_MEMORY)
 #   include "jemalloc.h"
-#endif  // MOZ_MEMORY
 
 using namespace mozilla;
 
@@ -498,11 +496,7 @@ nsJemallocFreeDirtyPagesRunnable::Run()
 {
   MOZ_ASSERT(NS_IsMainThread());
 
-#if defined(MOZ_JEMALLOC)
-  mallctl("arenas.purge", nullptr, 0, nullptr, 0);
-#elif defined(MOZ_MEMORY)
   jemalloc_free_dirty_pages();
-#endif
 
   return NS_OK;
 }