diff --git a/libmeminfo/include/meminfo/procmeminfo.h b/libmeminfo/include/meminfo/procmeminfo.h
index 95e5053..1fb4151 100644
--- a/libmeminfo/include/meminfo/procmeminfo.h
+++ b/libmeminfo/include/meminfo/procmeminfo.h
@@ -40,6 +40,11 @@
     const MemUsage& Usage();
     const MemUsage& Wss();
 
+    // Same as Maps() except, only valid for reading working set using CONFIG_IDLE_PAGE_TRACKING
+    // support in kernel. If the kernel support doesn't exist, the function will return an empty
+    // vector.
+    const std::vector<Vma>& MapsWithPageIdle();
+
     // Collect all 'vma' or 'maps' from /proc/<pid>/smaps and store them in 'maps_'. Returns a
     // constant reference to the vma vector after the collection is done.
     //
@@ -83,8 +88,8 @@
     ~ProcMemInfo() = default;
 
   private:
-    bool ReadMaps(bool get_wss);
-    bool ReadVmaStats(int pagemap_fd, Vma& vma, bool get_wss);
+    bool ReadMaps(bool get_wss, bool use_pageidle = false);
+    bool ReadVmaStats(int pagemap_fd, Vma& vma, bool get_wss, bool use_pageidle);
 
     pid_t pid_;
     bool get_wss_;
diff --git a/libmeminfo/procmeminfo.cpp b/libmeminfo/procmeminfo.cpp
index 1df03b2..069b6b3 100644
--- a/libmeminfo/procmeminfo.cpp
+++ b/libmeminfo/procmeminfo.cpp
@@ -121,6 +121,14 @@
     return maps_;
 }
 
+const std::vector<Vma>& ProcMemInfo::MapsWithPageIdle() {
+    if (maps_.empty() && !ReadMaps(get_wss_, true)) {
+        LOG(ERROR) << "Failed to read maps with page idle for Process " << pid_;
+    }
+
+    return maps_;
+}
+
 const std::vector<Vma>& ProcMemInfo::Smaps(const std::string& path) {
     if (!maps_.empty()) {
         return maps_;
@@ -226,7 +234,7 @@
     return true;
 }
 
-bool ProcMemInfo::ReadMaps(bool get_wss) {
+bool ProcMemInfo::ReadMaps(bool get_wss, bool use_pageidle) {
     // Each object reads /proc/<pid>/maps only once. This is done to make sure programs that are
     // running for the lifetime of the system can recycle the objects and don't have to
     // unnecessarily retain and update this object in memory (which can get significantly large).
@@ -256,7 +264,7 @@
     }
 
     for (auto& vma : maps_) {
-        if (!ReadVmaStats(pagemap_fd.get(), vma, get_wss)) {
+        if (!ReadVmaStats(pagemap_fd.get(), vma, get_wss, use_pageidle)) {
             LOG(ERROR) << "Failed to read page map for vma " << vma.name << "[" << vma.start << "-"
                        << vma.end << "]";
             maps_.clear();
@@ -268,7 +276,7 @@
     return true;
 }
 
-bool ProcMemInfo::ReadVmaStats(int pagemap_fd, Vma& vma, bool get_wss) {
+bool ProcMemInfo::ReadVmaStats(int pagemap_fd, Vma& vma, bool get_wss, bool use_pageidle) {
     PageAcct& pinfo = PageAcct::Instance();
     uint64_t pagesz = getpagesize();
     uint64_t num_pages = (vma.end - vma.start) / pagesz;
@@ -281,6 +289,13 @@
         return false;
     }
 
+    if (get_wss && use_pageidle) {
+        if (!pinfo.InitPageAcct(true)) {
+            LOG(ERROR) << "Failed to init idle page accounting";
+            return false;
+        }
+    }
+
     std::unique_ptr<uint64_t[]> pg_flags(new uint64_t[num_pages]);
     std::unique_ptr<uint64_t[]> pg_counts(new uint64_t[num_pages]);
     for (uint64_t i = 0; i < num_pages; ++i) {
@@ -323,7 +338,8 @@
         bool is_private = (pg_counts[i] == 1);
         // Working set
         if (get_wss) {
-            bool is_referenced = !!(pg_flags[i] & (1 << KPF_REFERENCED));
+            bool is_referenced = use_pageidle ? (pinfo.IsPageIdle(page_frame) == 1)
+                                              : !!(pg_flags[i] & (1 << KPF_REFERENCED));
             if (!is_referenced) {
                 continue;
             }
diff --git a/libmeminfo/tools/Android.bp b/libmeminfo/tools/Android.bp
index 24054c6..2e89c41 100644
--- a/libmeminfo/tools/Android.bp
+++ b/libmeminfo/tools/Android.bp
@@ -67,3 +67,17 @@
         "libmeminfo",
     ],
 }
+
+cc_binary {
+    name: "wsstop",
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+    srcs: ["wsstop.cpp"],
+    shared_libs: [
+        "libbase",
+        "liblog",
+        "libmeminfo",
+    ],
+}
diff --git a/libmeminfo/tools/wsstop.cpp b/libmeminfo/tools/wsstop.cpp
new file mode 100644
index 0000000..368d04e
--- /dev/null
+++ b/libmeminfo/tools/wsstop.cpp
@@ -0,0 +1,219 @@
+/*
+ * Copyright (C) 2019 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 <getopt.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <meminfo/pageacct.h>
+#include <meminfo/procmeminfo.h>
+
+using ::android::meminfo::ProcMemInfo;
+using ::android::meminfo::Vma;
+
+// Global options
+static int32_t g_delay = 0;
+static int32_t g_total = 2;
+static pid_t g_pid = -1;
+
+[[noreturn]] static void usage(int exit_status) {
+    fprintf(stderr,
+            "%s [-d DELAY_BETWEEN_EACH_SAMPLE] [-n REFRESH_TOTAL] PID\n"
+            "-d\tdelay between each working set sample (default 0)\n"
+            "-n\ttotal number of refreshes before we exit (default 2)\n",
+            getprogname());
+
+    exit(exit_status);
+}
+
+static void print_header() {
+    const char* addr1 = "           start              end ";
+    const char* addr2 = "            addr             addr ";
+
+    printf("%s  virtual                        shared    shared   private   private\n", addr1);
+    printf("%s     size       RSS       PSS     clean     dirty     clean     dirty      swap   "
+           "swapPSS",
+           addr2);
+    printf(" object\n");
+}
+
+static void print_divider() {
+    printf("---------------- ---------------- ");
+    printf("--------- --------- --------- --------- --------- --------- --------- --------- "
+           "--------- ");
+    printf("------------------------------\n");
+}
+
+static void print_vma(const Vma& v) {
+    printf("%16" PRIx64 " %16" PRIx64 " ", v.start, v.end);
+    printf("%8" PRIu64 "K %8" PRIu64 "K %8" PRIu64 "K %8" PRIu64 "K %8" PRIu64 "K %8" PRIu64
+           "K %8" PRIu64 "K %8" PRIu64 "K %8" PRIu64 "K ",
+           v.usage.vss / 1024, v.usage.rss / 1024, v.usage.pss / 1024, v.usage.shared_clean / 1024,
+           v.usage.shared_dirty / 1024, v.usage.private_clean / 1024, v.usage.private_dirty / 1024,
+           v.usage.swap / 1024, v.usage.swap_pss / 1024);
+    printf("%s\n", v.name.c_str());
+}
+
+static bool same_vma(const Vma& cur, const Vma& last) {
+    return (cur.start == last.start && cur.end == last.end && cur.name == last.name &&
+            cur.flags == last.flags && cur.offset == last.offset);
+}
+
+static Vma diff_vma_params(const Vma& cur, const Vma& last) {
+    Vma res;
+    res.usage.shared_clean = cur.usage.shared_clean > last.usage.shared_clean
+                                     ? cur.usage.shared_clean - last.usage.shared_clean
+                                     : 0;
+    res.usage.shared_dirty = cur.usage.shared_dirty > last.usage.shared_dirty
+                                     ? cur.usage.shared_dirty - last.usage.shared_dirty
+                                     : 0;
+    res.usage.private_clean = cur.usage.private_clean > last.usage.private_clean
+                                      ? cur.usage.private_clean - last.usage.private_clean
+                                      : 0;
+    res.usage.private_dirty = cur.usage.private_dirty > last.usage.private_dirty
+                                      ? cur.usage.private_dirty - last.usage.private_dirty
+                                      : 0;
+
+    res.usage.rss = cur.usage.rss > last.usage.rss ? cur.usage.rss - last.usage.rss : 0;
+    res.usage.pss = cur.usage.pss > last.usage.pss ? cur.usage.pss - last.usage.pss : 0;
+    res.usage.uss = cur.usage.uss > last.usage.uss ? cur.usage.uss - last.usage.uss : 0;
+    res.usage.swap = cur.usage.swap > last.usage.swap ? cur.usage.swap - last.usage.swap : 0;
+    res.usage.swap_pss =
+            cur.usage.swap_pss > last.usage.swap_pss ? cur.usage.swap_pss - last.usage.swap_pss : 0;
+
+    // set vma properties to the same as the current one.
+    res.start = cur.start;
+    res.end = cur.end;
+    res.offset = cur.offset;
+    res.flags = cur.flags;
+    res.name = cur.name;
+    return res;
+}
+
+static void diff_workingset(std::vector<Vma>& wss, std::vector<Vma>& old, std::vector<Vma>* res) {
+    res->clear();
+    auto vma_sorter = [](const Vma& a, const Vma& b) { return a.start < b.start; };
+    std::sort(wss.begin(), wss.end(), vma_sorter);
+    std::sort(old.begin(), old.end(), vma_sorter);
+    if (old.empty()) {
+        *res = wss;
+        return;
+    }
+
+    for (auto& i : wss) {
+        bool found_same_vma = false;
+        // TODO: This is highly inefficient, fix it if it takes
+        // too long. Worst case will be system_server
+        for (auto& j : old) {
+            if (same_vma(i, j)) {
+                res->emplace_back(diff_vma_params(i, j));
+                found_same_vma = true;
+                break;
+            }
+        }
+
+        if (!found_same_vma) {
+            res->emplace_back(i);
+        }
+    }
+
+    std::sort(res->begin(), res->end(), vma_sorter);
+    return;
+}
+
+static int workingset() {
+    std::vector<Vma> last_wss = {};
+    std::vector<Vma> diff_wss = {};
+    uint32_t nr_refresh = 0;
+
+    while (true) {
+        std::unique_ptr<ProcMemInfo> proc_mem = std::make_unique<ProcMemInfo>(g_pid, true);
+        std::vector<Vma> wss = proc_mem->MapsWithPageIdle();
+
+        diff_workingset(wss, last_wss, &diff_wss);
+        diff_wss.erase(std::remove_if(diff_wss.begin(), diff_wss.end(),
+                                      [](const auto& v) { return v.usage.rss == 0; }),
+                       diff_wss.end());
+        if ((nr_refresh % 5) == 0) {
+            print_header();
+            print_divider();
+        }
+
+        for (const auto& v : diff_wss) {
+            print_vma(v);
+        }
+
+        nr_refresh++;
+        if (nr_refresh == g_total) {
+            break;
+        }
+
+        last_wss = wss;
+        sleep(g_delay);
+        print_divider();
+    }
+
+    return 0;
+}
+
+int main(int argc, char* argv[]) {
+    struct option longopts[] = {
+            {"help", no_argument, nullptr, 'h'},
+            {0, 0, nullptr, 0},
+    };
+
+    int opt;
+    while ((opt = getopt_long(argc, argv, "d:n:h", longopts, nullptr)) != -1) {
+        switch (opt) {
+            case 'd':
+                g_delay = atoi(optarg);
+                break;
+            case 'n':
+                g_total = atoi(optarg);
+                break;
+            case 'h':
+                usage(EXIT_SUCCESS);
+            default:
+                usage(EXIT_FAILURE);
+        }
+    }
+
+    if ((argc - 1) < optind) {
+        fprintf(stderr, "Invalid arguments: Must provide <pid> at the end\n");
+        usage(EXIT_FAILURE);
+    }
+
+    g_pid = atoi(argv[optind]);
+    if (g_pid <= 0) {
+        fprintf(stderr, "Invalid process id %s\n", argv[optind]);
+        usage(EXIT_FAILURE);
+    }
+
+    if (!::android::meminfo::PageAcct::KernelHasPageIdle()) {
+        fprintf(stderr, "Missing support for Idle page tracking in the kernel\n");
+        return 0;
+    }
+
+    return workingset();
+}