diff --git a/include/cutils/multiuser.h b/include/cutils/multiuser.h
index 7e7f815..4f23776 100644
--- a/include/cutils/multiuser.h
+++ b/include/cutils/multiuser.h
@@ -23,19 +23,19 @@
 extern "C" {
 #endif
 
-// NOTE: keep in sync with android.os.UserId
-
-#define MULTIUSER_APP_PER_USER_RANGE 100000
-#define MULTIUSER_FIRST_SHARED_APPLICATION_GID 50000
-#define MULTIUSER_FIRST_APPLICATION_UID 10000
-
 typedef uid_t userid_t;
 typedef uid_t appid_t;
 
 extern userid_t multiuser_get_user_id(uid_t uid);
 extern appid_t multiuser_get_app_id(uid_t uid);
-extern uid_t multiuser_get_uid(userid_t userId, appid_t appId);
-extern appid_t multiuser_get_shared_app_gid(uid_t uid);
+
+extern uid_t multiuser_get_uid(userid_t user_id, appid_t app_id);
+
+extern gid_t multiuser_get_cache_gid(userid_t user_id, appid_t app_id);
+extern gid_t multiuser_get_shared_gid(userid_t user_id, appid_t app_id);
+
+/* TODO: switch callers over to multiuser_get_shared_gid() */
+extern gid_t multiuser_get_shared_app_gid(uid_t uid);
 
 #ifdef __cplusplus
 }
diff --git a/include/private/android_filesystem_config.h b/include/private/android_filesystem_config.h
index 3031562..f7cf9b8 100644
--- a/include/private/android_filesystem_config.h
+++ b/include/private/android_filesystem_config.h
@@ -157,15 +157,21 @@
 #define AID_MISC          9998  /* access to misc storage */
 #define AID_NOBODY        9999
 
-#define AID_APP          10000  /* first app user */
+#define AID_APP              10000 /* TODO: switch users over to AID_APP_START */
+#define AID_APP_START        10000 /* first app user */
+#define AID_APP_END          19999 /* last app user */
 
-#define AID_ISOLATED_START 99000 /* start of uids for fully isolated sandboxed processes */
-#define AID_ISOLATED_END   99999 /* end of uids for fully isolated sandboxed processes */
-
-#define AID_USER        100000  /* offset for uid ranges for each user */
+#define AID_CACHE_GID_START  20000 /* start of gids for apps to mark cached data */
+#define AID_CACHE_GID_END    29999 /* end of gids for apps to mark cached data */
 
 #define AID_SHARED_GID_START 50000 /* start of gids for apps in each user to share */
-#define AID_SHARED_GID_END   59999 /* start of gids for apps in each user to share */
+#define AID_SHARED_GID_END   59999 /* end of gids for apps in each user to share */
+
+#define AID_ISOLATED_START   99000 /* start of uids for fully isolated sandboxed processes */
+#define AID_ISOLATED_END     99999 /* end of uids for fully isolated sandboxed processes */
+
+#define AID_USER            100000 /* TODO: switch users over to AID_USER_OFFSET */
+#define AID_USER_OFFSET     100000 /* offset for uid ranges for each user */
 
 #if !defined(EXCLUDE_FS_CONFIG_STRUCTURES)
 /*
diff --git a/libcutils/multiuser.c b/libcutils/multiuser.c
index 0f4427b..0ef337d 100644
--- a/libcutils/multiuser.c
+++ b/libcutils/multiuser.c
@@ -15,21 +15,36 @@
  */
 
 #include <cutils/multiuser.h>
+#include <private/android_filesystem_config.h>
 
 userid_t multiuser_get_user_id(uid_t uid) {
-    return uid / MULTIUSER_APP_PER_USER_RANGE;
+    return uid / AID_USER_OFFSET;
 }
 
 appid_t multiuser_get_app_id(uid_t uid) {
-    return uid % MULTIUSER_APP_PER_USER_RANGE;
+    return uid % AID_USER_OFFSET;
 }
 
-uid_t multiuser_get_uid(userid_t userId, appid_t appId) {
-    return userId * MULTIUSER_APP_PER_USER_RANGE + (appId % MULTIUSER_APP_PER_USER_RANGE);
+uid_t multiuser_get_uid(userid_t user_id, appid_t app_id) {
+    return (user_id * AID_USER_OFFSET) + (app_id % AID_USER_OFFSET);
 }
 
-appid_t multiuser_get_shared_app_gid(uid_t id) {
-  return MULTIUSER_FIRST_SHARED_APPLICATION_GID + (id % MULTIUSER_APP_PER_USER_RANGE)
-          - MULTIUSER_FIRST_APPLICATION_UID;
+gid_t multiuser_get_cache_gid(userid_t user_id, appid_t app_id) {
+    if (app_id >= AID_APP_START && app_id <= AID_APP_END) {
+        return multiuser_get_uid(user_id, (app_id - AID_APP_START) + AID_CACHE_GID_START);
+    } else {
+        return -1;
+    }
+}
 
+gid_t multiuser_get_shared_gid(userid_t user_id, appid_t app_id) {
+    if (app_id >= AID_APP_START && app_id <= AID_APP_END) {
+        return multiuser_get_uid(user_id, (app_id - AID_APP_START) + AID_SHARED_GID_START);
+    } else {
+        return -1;
+    }
+}
+
+gid_t multiuser_get_shared_app_gid(uid_t uid) {
+    return multiuser_get_shared_gid(multiuser_get_user_id(uid), multiuser_get_app_id(uid));
 }
diff --git a/libcutils/tests/Android.bp b/libcutils/tests/Android.bp
index abe3c21..0b0dc09 100644
--- a/libcutils/tests/Android.bp
+++ b/libcutils/tests/Android.bp
@@ -26,7 +26,8 @@
                 "trace-dev_test.cpp",
                 "test_str_parms.cpp",
                 "android_get_control_socket_test.cpp",
-                "android_get_control_file_test.cpp"
+                "android_get_control_file_test.cpp",
+                "multiuser_test.cpp"
             ],
         },
 
diff --git a/libcutils/tests/multiuser_test.cpp b/libcutils/tests/multiuser_test.cpp
new file mode 100644
index 0000000..2307ea8
--- /dev/null
+++ b/libcutils/tests/multiuser_test.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <cutils/multiuser.h>
+#include <gtest/gtest.h>
+
+TEST(MultiuserTest, TestMerge) {
+    EXPECT_EQ(0, multiuser_get_uid(0, 0));
+    EXPECT_EQ(1000, multiuser_get_uid(0, 1000));
+    EXPECT_EQ(10000, multiuser_get_uid(0, 10000));
+    EXPECT_EQ(50000, multiuser_get_uid(0, 50000));
+    EXPECT_EQ(1000000, multiuser_get_uid(10, 0));
+    EXPECT_EQ(1001000, multiuser_get_uid(10, 1000));
+    EXPECT_EQ(1010000, multiuser_get_uid(10, 10000));
+    EXPECT_EQ(1050000, multiuser_get_uid(10, 50000));
+}
+
+TEST(MultiuserTest, TestSplitUser) {
+    EXPECT_EQ(0, multiuser_get_user_id(0));
+    EXPECT_EQ(0, multiuser_get_user_id(1000));
+    EXPECT_EQ(0, multiuser_get_user_id(10000));
+    EXPECT_EQ(0, multiuser_get_user_id(50000));
+    EXPECT_EQ(10, multiuser_get_user_id(1000000));
+    EXPECT_EQ(10, multiuser_get_user_id(1001000));
+    EXPECT_EQ(10, multiuser_get_user_id(1010000));
+    EXPECT_EQ(10, multiuser_get_user_id(1050000));
+}
+
+TEST(MultiuserTest, TestSplitApp) {
+    EXPECT_EQ(0, multiuser_get_app_id(0));
+    EXPECT_EQ(1000, multiuser_get_app_id(1000));
+    EXPECT_EQ(10000, multiuser_get_app_id(10000));
+    EXPECT_EQ(50000, multiuser_get_app_id(50000));
+    EXPECT_EQ(0, multiuser_get_app_id(1000000));
+    EXPECT_EQ(1000, multiuser_get_app_id(1001000));
+    EXPECT_EQ(10000, multiuser_get_app_id(1010000));
+    EXPECT_EQ(50000, multiuser_get_app_id(1050000));
+}
+
+TEST(MultiuserTest, TestCache) {
+    EXPECT_EQ(-1, multiuser_get_cache_gid(0, 0));
+    EXPECT_EQ(-1, multiuser_get_cache_gid(0, 1000));
+    EXPECT_EQ(20000, multiuser_get_cache_gid(0, 10000));
+    EXPECT_EQ(-1, multiuser_get_cache_gid(0, 50000));
+    EXPECT_EQ(1020000, multiuser_get_cache_gid(10, 10000));
+}
+
+TEST(MultiuserTest, TestShared) {
+    EXPECT_EQ(-1, multiuser_get_shared_gid(0, 0));
+    EXPECT_EQ(-1, multiuser_get_shared_gid(0, 1000));
+    EXPECT_EQ(50000, multiuser_get_shared_gid(0, 10000));
+    EXPECT_EQ(-1, multiuser_get_shared_gid(0, 50000));
+    EXPECT_EQ(1050000, multiuser_get_shared_gid(10, 10000));
+}
diff --git a/logd/LogStatistics.cpp b/logd/LogStatistics.cpp
index bab87ba..3c8bd75 100644
--- a/logd/LogStatistics.cpp
+++ b/logd/LogStatistics.cpp
@@ -182,7 +182,7 @@
     }
 
     // Parse /data/system/packages.list
-    uid_t userId = uid % AID_USER;
+    uid_t userId = uid % AID_USER_OFFSET;
     const char *name = android::uidToName(userId);
     if (!name && (userId > (AID_SHARED_GID_START - AID_APP))) {
         name = android::uidToName(userId - (AID_SHARED_GID_START - AID_APP));
diff --git a/run-as/run-as.cpp b/run-as/run-as.cpp
index aec51f4..e7b8cc2 100644
--- a/run-as/run-as.cpp
+++ b/run-as/run-as.cpp
@@ -165,12 +165,12 @@
   if (setegid(old_egid) == -1) error(1, errno, "couldn't restore egid");
 
   // Verify that user id is not too big.
-  if ((UID_MAX - info.uid) / AID_USER < (uid_t)userId) {
+  if ((UID_MAX - info.uid) / AID_USER_OFFSET < (uid_t)userId) {
     error(1, 0, "user id too big: %d", userId);
   }
 
   // Calculate user app ID.
-  uid_t userAppId = (AID_USER * userId) + info.uid;
+  uid_t userAppId = (AID_USER_OFFSET * userId) + info.uid;
 
   // Reject system packages.
   if (userAppId < AID_APP) {