diff --git a/cmds/atrace/atrace.cpp b/cmds/atrace/atrace.cpp
index 07a6adb..1b90579 100644
--- a/cmds/atrace/atrace.cpp
+++ b/cmds/atrace/atrace.cpp
@@ -152,6 +152,8 @@
     { "freq",       "CPU Frequency",    0, {
         { REQ,      "events/power/cpu_frequency/enable" },
         { OPT,      "events/power/clock_set_rate/enable" },
+        { OPT,      "events/power/clock_disable/enable" },
+        { OPT,      "events/power/clock_enable/enable" },
         { OPT,      "events/power/cpu_frequency_limits/enable" },
     } },
     { "membus",     "Memory Bus Utilization", 0, {
diff --git a/services/surfaceflinger/Android.mk b/services/surfaceflinger/Android.mk
index d9bca04..3f8ab3f 100644
--- a/services/surfaceflinger/Android.mk
+++ b/services/surfaceflinger/Android.mk
@@ -21,6 +21,7 @@
     MonitoredProducer.cpp \
     SurfaceFlingerConsumer.cpp \
     SurfaceInterceptor.cpp \
+    SurfaceTracing.cpp \
     Transform.cpp \
     DisplayHardware/ComposerHal.cpp \
     DisplayHardware/FramebufferSurface.cpp \
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 5405971..0525607 100755
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -1868,6 +1868,10 @@
     mCurrentState.modified = true;
     mCurrentState.z = z;
 
+    auto oldZOrderRelativeOf = mCurrentState.zOrderRelativeOf.promote();
+    if (oldZOrderRelativeOf != nullptr) {
+        oldZOrderRelativeOf->removeZOrderRelative(this);
+    }
     mCurrentState.zOrderRelativeOf = relative;
     relative->addZOrderRelative(this);
 
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index a38e3b3..77b9a29 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1520,6 +1520,7 @@
     rebuildLayerStacks();
     setUpHWComposer();
     doDebugFlashRegions();
+    doTracing("handleRefresh");
     doComposition();
     postComposition(refreshStartTime);
 
@@ -1579,6 +1580,14 @@
     }
 }
 
+void SurfaceFlinger::doTracing(const char* where) {
+    ATRACE_CALL();
+    ATRACE_NAME(where);
+    if (CC_UNLIKELY(mTracing.isEnabled())) {
+        mTracing.traceLayers(where, dumpProtoInfo());
+    }
+}
+
 void SurfaceFlinger::preComposition(nsecs_t refreshStartTime)
 {
     ATRACE_CALL();
@@ -4225,6 +4234,20 @@
                 reply->writeBool(hasWideColorDisplay);
                 return NO_ERROR;
             }
+            case 1025: { // tracing
+                n = data.readInt32();
+                if (n) {
+                    ALOGV("LayerTracing enabled");
+                    mTracing.enable();
+                    doTracing("tracing.enable");
+                    reply->writeInt32(NO_ERROR);
+                } else {
+                    ALOGV("LayerTracing disabled");
+                    status_t err = mTracing.disable();
+                    reply->writeInt32(err);
+                }
+                return NO_ERROR;
+            }
         }
     }
     return err;
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 25ccb89..d0f4699 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -60,6 +60,7 @@
 #include "LayerVector.h"
 #include "MessageQueue.h"
 #include "SurfaceInterceptor.h"
+#include "SurfaceTracing.h"
 #include "StartPropertySetThread.h"
 
 #ifdef USE_HWC2
@@ -575,6 +576,7 @@
     void setUpHWComposer();
     void doComposition();
     void doDebugFlashRegions();
+    void doTracing(const char* where);
     void doDisplayComposition(const sp<const DisplayDevice>& displayDevice, const Region& dirtyRegion);
 
     // compose surfaces for display hw. this fails if using GL and the surface
@@ -746,6 +748,7 @@
     bool mPropagateBackpressure = true;
 #endif
     SurfaceInterceptor mInterceptor;
+    SurfaceTracing mTracing;
     bool mUseHwcVirtualDisplays = false;
 
     // Restrict layers to use two buffers in their bufferqueues.
diff --git a/services/surfaceflinger/SurfaceTracing.cpp b/services/surfaceflinger/SurfaceTracing.cpp
new file mode 100644
index 0000000..f8c466e
--- /dev/null
+++ b/services/surfaceflinger/SurfaceTracing.cpp
@@ -0,0 +1,85 @@
+/*
+ * Copyright 2017 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.
+ */
+#undef LOG_TAG
+#define LOG_TAG "SurfaceTracing"
+#define ATRACE_TAG ATRACE_TAG_GRAPHICS
+
+#include "SurfaceTracing.h"
+
+#include <android-base/file.h>
+#include <log/log.h>
+#include <utils/SystemClock.h>
+#include <utils/Trace.h>
+
+namespace android {
+
+void SurfaceTracing::enable() {
+    if (mEnabled) {
+        return;
+    }
+    ATRACE_CALL();
+    mEnabled = true;
+    std::lock_guard<std::mutex> protoGuard(mTraceMutex);
+
+    mTrace.set_magic_number(uint64_t(LayersTraceFileProto_MagicNumber_MAGIC_NUMBER_H) << 32 |
+                            LayersTraceFileProto_MagicNumber_MAGIC_NUMBER_L);
+}
+
+status_t SurfaceTracing::disable() {
+    if (!mEnabled) {
+        return NO_ERROR;
+    }
+    ATRACE_CALL();
+    std::lock_guard<std::mutex> protoGuard(mTraceMutex);
+    mEnabled = false;
+    status_t err(writeProtoFileLocked());
+    ALOGE_IF(err == PERMISSION_DENIED, "Could not save the proto file! Permission denied");
+    ALOGE_IF(err == NOT_ENOUGH_DATA, "Could not save the proto file! There are missing fields");
+    mTrace.Clear();
+    return err;
+}
+
+bool SurfaceTracing::isEnabled() {
+    return mEnabled;
+}
+
+void SurfaceTracing::traceLayers(const char* where, LayersProto layers) {
+    std::lock_guard<std::mutex> protoGuard(mTraceMutex);
+
+    LayersTraceProto* entry = mTrace.add_entry();
+    entry->set_elapsed_realtime_nanos(elapsedRealtimeNano());
+    entry->set_where(where);
+    entry->mutable_layers()->Swap(&layers);
+}
+
+status_t SurfaceTracing::writeProtoFileLocked() {
+    ATRACE_CALL();
+
+    if (!mTrace.IsInitialized()) {
+        return NOT_ENOUGH_DATA;
+    }
+    std::string output;
+    if (!mTrace.SerializeToString(&output)) {
+        return PERMISSION_DENIED;
+    }
+    if (!android::base::WriteStringToFile(output, mOutputFileName, true)) {
+        return PERMISSION_DENIED;
+    }
+
+    return NO_ERROR;
+}
+
+} // namespace android
diff --git a/services/surfaceflinger/SurfaceTracing.h b/services/surfaceflinger/SurfaceTracing.h
new file mode 100644
index 0000000..9b21989
--- /dev/null
+++ b/services/surfaceflinger/SurfaceTracing.h
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2017 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.
+ */
+
+#pragma once
+
+#include <layerproto/LayerProtoHeader.h>
+#include <utils/Errors.h>
+
+#include <mutex>
+
+using namespace android::surfaceflinger;
+
+namespace android {
+
+/*
+ * SurfaceTracing records layer states during surface flinging.
+ */
+class SurfaceTracing {
+public:
+    void enable();
+    status_t disable();
+    bool isEnabled();
+
+    void traceLayers(const char* where, LayersProto);
+
+private:
+    static constexpr auto DEFAULT_FILENAME = "/data/misc/trace/layerstrace.pb";
+
+    status_t writeProtoFileLocked();
+
+    bool mEnabled = false;
+    std::string mOutputFileName = DEFAULT_FILENAME;
+    std::mutex mTraceMutex;
+    LayersTraceFileProto mTrace;
+};
+
+} // namespace android
diff --git a/services/surfaceflinger/layerproto/Android.bp b/services/surfaceflinger/layerproto/Android.bp
index 4c52bdf..8eb218c 100644
--- a/services/surfaceflinger/layerproto/Android.bp
+++ b/services/surfaceflinger/layerproto/Android.bp
@@ -6,6 +6,7 @@
     srcs: [
         "LayerProtoParser.cpp",
         "layers.proto",
+        "layerstrace.proto",
     ],
 
     shared_libs: [
diff --git a/services/surfaceflinger/layerproto/include/layerproto/LayerProtoHeader.h b/services/surfaceflinger/layerproto/include/layerproto/LayerProtoHeader.h
index 054d4f2..f560562 100644
--- a/services/surfaceflinger/layerproto/include/layerproto/LayerProtoHeader.h
+++ b/services/surfaceflinger/layerproto/include/layerproto/LayerProtoHeader.h
@@ -21,3 +21,4 @@
 // This file should be included instead of directly including layer.b.h
 #pragma GCC system_header
 #include <layers.pb.h>
+#include <layerstrace.pb.h>
diff --git a/services/surfaceflinger/layerproto/layerstrace.proto b/services/surfaceflinger/layerproto/layerstrace.proto
new file mode 100644
index 0000000..bee17d2
--- /dev/null
+++ b/services/surfaceflinger/layerproto/layerstrace.proto
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+
+import "frameworks/native/services/surfaceflinger/layerproto/layers.proto";
+
+package android.surfaceflinger;
+
+/* represents a file full of surface flinger trace entries.
+   Encoded, it should start with 0x4c 0x59 0x52 0x54 0x52 0x41 0x43 0x45 (.LYRTRACE), such
+   that they can be easily identified. */
+message LayersTraceFileProto {
+
+    /* constant; MAGIC_NUMBER = (long) MAGIC_NUMBER_H << 32 | MagicNumber.MAGIC_NUMBER_L
+       (this is needed because enums have to be 32 bits and there's no nice way to put 64bit
+        constants into .proto files. */
+    enum MagicNumber {
+        INVALID = 0;
+        MAGIC_NUMBER_L = 0x5452594c;  /* LYRT (little-endian ASCII) */
+        MAGIC_NUMBER_H = 0x45434152;  /* RACE (little-endian ASCII) */
+    }
+
+    optional fixed64 magic_number = 1;  /* Must be the first field, set to value in MagicNumber */
+    repeated LayersTraceProto entry = 2;
+}
+
+/* one window manager trace entry. */
+message LayersTraceProto {
+    /* required: elapsed realtime in nanos since boot of when this entry was logged */
+    optional fixed64 elapsed_realtime_nanos = 1;
+
+    /* where the trace originated */
+    optional string where = 2;
+
+    optional LayersProto layers = 3;
+}