Merge "Switch to purge all unused memory to kernel." am: 2325b1da98 am: 861aa1f9d5

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2461533

Change-Id: I5ce9c3c59259dac9b5734d7570cb9fa359ec1d1e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

core/jni/com_android_internal_os_Zygote.cpp

@@ -2296,7 +2296,9 @@ pid_t zygote::ForkCommon(JNIEnv* env, bool is_system_server,
     // region shared with the child process we reduce the number of pages that
     // transition to the private-dirty state when malloc adjusts the meta-data
     // on each of the pages it is managing after the fork.
-    mallopt(M_PURGE, 0);
+    if (mallopt(M_PURGE_ALL, 0) != 1) {
+      mallopt(M_PURGE, 0);
+    }
   }
 
   pid_t pid = fork();