diff --git a/include/cpustats/ThreadCpuUsage.h b/include/cpustats/ThreadCpuUsage.h
index 24012a4..9cd93d8 100644
--- a/include/cpustats/ThreadCpuUsage.h
+++ b/include/cpustats/ThreadCpuUsage.h
@@ -17,16 +17,17 @@
 #ifndef _THREAD_CPU_USAGE_H
 #define _THREAD_CPU_USAGE_H
 
-#include <cpustats/CentralTendencyStatistics.h>
+#include <fcntl.h>
+#include <pthread.h>
 
-// Track CPU usage for the current thread, and maintain statistics on
-// the CPU usage.  Units are in per-thread CPU ns, as reported by
+namespace android {
+
+// Track CPU usage for the current thread.
+// Units are in per-thread CPU ns, as reported by
 // clock_gettime(CLOCK_THREAD_CPUTIME_ID).  Simple usage: for cyclic
 // threads where you want to measure the execution time of the whole
 // cycle, just call sampleAndEnable() at the start of each cycle.
-// Then call statistics() to get the results, and resetStatistics()
-// to start a new set of measurements.
-// For acyclic threads, or for cyclic threads where you want to measure
+// For acyclic threads, or for cyclic threads where you want to measure/track
 // only part of each cycle, call enable(), disable(), and/or setEnabled()
 // to demarcate the region(s) of interest, and then call sample() periodically.
 // This class is not thread-safe for concurrent calls from multiple threads;
@@ -44,13 +45,17 @@
         // mPreviousTs
         // mMonotonicTs
         mMonotonicKnown(false)
-        // mStatistics
-        { }
+        {
+            (void) pthread_once(&sOnceControl, &init);
+            for (int i = 0; i < sKernelMax; ++i) {
+                mCurrentkHz[i] = (uint32_t) ~0;   // unknown
+            }
+        }
 
     ~ThreadCpuUsage() { }
 
     // Return whether currently tracking CPU usage by current thread
-    bool isEnabled()    { return mIsEnabled; }
+    bool isEnabled() const  { return mIsEnabled; }
 
     // Enable tracking of CPU usage by current thread;
     // any CPU used from this point forward will be tracked.
@@ -66,39 +71,52 @@
     // This method is intended to be used for safe nested enable/disabling.
     bool setEnabled(bool isEnabled);
 
-    // Add a sample point for central tendency statistics, and also
-    // enable tracking if needed.  If tracking has never been enabled, then
-    // enables tracking but does not add a sample (it is not possible to add
-    // a sample the first time because no previous).  Otherwise if tracking is
-    // enabled, then adds a sample for tracked CPU ns since the previous
+    // Add a sample point, and also enable tracking if needed.
+    // If tracking has never been enabled, then this call enables tracking but
+    // does _not_ add a sample -- it is not possible to add a sample the
+    // first time because there is no previous point to subtract from.
+    // Otherwise, if tracking is enabled,
+    // then adds a sample for tracked CPU ns since the previous
     // sample, or since the first call to sampleAndEnable(), enable(), or
     // setEnabled(true).  If there was a previous sample but tracking is
     // now disabled, then adds a sample for the tracked CPU ns accumulated
     // up until the most recent disable(), resets this accumulator, and then
     // enables tracking.  Calling this method rather than enable() followed
     // by sample() avoids a race condition for the first sample.
-    void sampleAndEnable();
+    // Returns true if the sample 'ns' is valid, or false if invalid.
+    // Note that 'ns' is an output parameter passed by reference.
+    // The caller does not need to initialize this variable.
+    // The units are CPU nanoseconds consumed by current thread.
+    bool sampleAndEnable(double& ns);
 
-    // Add a sample point for central tendency statistics, but do not
+    // Add a sample point, but do not
     // change the tracking enabled status.  If tracking has either never been
     // enabled, or has never been enabled since the last sample, then log a warning
     // and don't add sample.  Otherwise, adds a sample for tracked CPU ns since
     // the previous sample or since the first call to sampleAndEnable(),
     // enable(), or setEnabled(true) if no previous sample.
-    void sample();
+    // Returns true if the sample is valid, or false if invalid.
+    // Note that 'ns' is an output parameter passed by reference.
+    // The caller does not need to initialize this variable.
+    // The units are CPU nanoseconds consumed by current thread.
+    bool sample(double& ns);
 
-    // Return the elapsed delta wall clock ns since initial enable or statistics reset,
+    // Return the elapsed delta wall clock ns since initial enable or reset,
     // as reported by clock_gettime(CLOCK_MONOTONIC).
     long long elapsed() const;
 
-    // Reset statistics and elapsed.  Has no effect on tracking or accumulator.
-    void resetStatistics();
+    // Reset elapsed wall clock.  Has no effect on tracking or accumulator.
+    void resetElapsed();
 
-    // Return a const reference to the central tendency statistics.
-    // Note that only the const methods can be called on this object.
-    const CentralTendencyStatistics& statistics() const {
-        return mStatistics;
-    }
+    // Return current clock frequency for specified CPU, in kHz.
+    // You can get your CPU number using sched_getcpu(2).  Note that, unless CPU affinity
+    // has been configured appropriately, the CPU number can change.
+    // Also note that, unless the CPU governor has been configured appropriately,
+    // the CPU frequency can change.  And even if the CPU frequency is locked down
+    // to a particular value, that the frequency might still be adjusted
+    // to prevent thermal overload.  Therefore you should poll for your thread's
+    // current CPU number and clock frequency periodically.
+    uint32_t getCpukHz(int cpuNum);
 
 private:
     bool mIsEnabled;                // whether tracking is currently enabled
@@ -107,7 +125,15 @@
     struct timespec mPreviousTs;    // most recent thread CPU time, valid only if mIsEnabled is true
     struct timespec mMonotonicTs;   // most recent monotonic time
     bool mMonotonicKnown;           // whether mMonotonicTs has been set
-    CentralTendencyStatistics mStatistics;
+
+    static const int MAX_CPU = 8;
+    static int sScalingFds[MAX_CPU];// file descriptor per CPU for reading scaling_cur_freq
+    uint32_t mCurrentkHz[MAX_CPU];  // current CPU frequency in kHz, not static to avoid a race
+    static pthread_once_t sOnceControl;
+    static int sKernelMax;          // like MAX_CPU, but determined at runtime == cpu/kernel_max + 1
+    static void init();
 };
 
+}   // namespace android
+
 #endif //  _THREAD_CPU_USAGE_H
diff --git a/libs/cpustats/ThreadCpuUsage.cpp b/libs/cpustats/ThreadCpuUsage.cpp
index ffee039..99b4c8363 100644
--- a/libs/cpustats/ThreadCpuUsage.cpp
+++ b/libs/cpustats/ThreadCpuUsage.cpp
@@ -14,18 +14,26 @@
  * limitations under the License.
  */
 
+#define LOG_TAG "ThreadCpuUsage"
+//#define LOG_NDEBUG 0
+
 #include <errno.h>
+#include <stdlib.h>
 #include <time.h>
 
+#include <utils/Debug.h>
 #include <utils/Log.h>
 
 #include <cpustats/ThreadCpuUsage.h>
 
+namespace android {
+
 bool ThreadCpuUsage::setEnabled(bool isEnabled)
 {
     bool wasEnabled = mIsEnabled;
     // only do something if there is a change
     if (isEnabled != wasEnabled) {
+        ALOGV("setEnabled(%d)", isEnabled);
         int rc;
         // enabling
         if (isEnabled) {
@@ -65,20 +73,28 @@
     return wasEnabled;
 }
 
-void ThreadCpuUsage::sampleAndEnable()
+bool ThreadCpuUsage::sampleAndEnable(double& ns)
 {
+    bool ret;
     bool wasEverEnabled = mWasEverEnabled;
     if (enable()) {
         // already enabled, so add a new sample relative to previous
-        sample();
+        return sample(ns);
     } else if (wasEverEnabled) {
         // was disabled, but add sample for accumulated time while enabled
-        mStatistics.sample((double) mAccumulator);
+        ns = (double) mAccumulator;
         mAccumulator = 0;
+        ALOGV("sampleAndEnable %.0f", ns);
+        return true;
+    } else {
+        // first time called
+        ns = 0.0;
+        ALOGV("sampleAndEnable false");
+        return false;
     }
 }
 
-void ThreadCpuUsage::sample()
+bool ThreadCpuUsage::sample(double &ns)
 {
     if (mWasEverEnabled) {
         if (mIsEnabled) {
@@ -87,6 +103,8 @@
             rc = clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts);
             if (rc) {
                 ALOGE("clock_gettime(CLOCK_THREAD_CPUTIME_ID) errno=%d", errno);
+                ns = 0.0;
+                return false;
             } else {
                 long long delta = (ts.tv_sec - mPreviousTs.tv_sec) * 1000000000LL +
                         (ts.tv_nsec - mPreviousTs.tv_nsec);
@@ -96,10 +114,14 @@
         } else {
             mWasEverEnabled = false;
         }
-        mStatistics.sample((double) mAccumulator);
+        ns = (double) mAccumulator;
+        ALOGV("sample %.0f", ns);
         mAccumulator = 0;
+        return true;
     } else {
         ALOGW("Can't add sample because measurements have never been enabled");
+        ns = 0.0;
+        return false;
     }
 }
 
@@ -122,12 +144,13 @@
         ALOGW("Can't compute elapsed time because measurements have never been enabled");
         elapsed = 0;
     }
+    ALOGV("elapsed %lld", elapsed);
     return elapsed;
 }
 
-void ThreadCpuUsage::resetStatistics()
+void ThreadCpuUsage::resetElapsed()
 {
-    mStatistics.reset();
+    ALOGV("resetElapsed");
     if (mMonotonicKnown) {
         int rc;
         rc = clock_gettime(CLOCK_MONOTONIC, &mMonotonicTs);
@@ -137,3 +160,93 @@
         }
     }
 }
+
+/*static*/
+int ThreadCpuUsage::sScalingFds[ThreadCpuUsage::MAX_CPU];
+pthread_once_t ThreadCpuUsage::sOnceControl = PTHREAD_ONCE_INIT;
+int ThreadCpuUsage::sKernelMax;
+
+/*static*/
+void ThreadCpuUsage::init()
+{
+    // read the number of CPUs
+    sKernelMax = 1;
+    int fd = open("/sys/devices/system/cpu/kernel_max", O_RDONLY);
+    if (fd >= 0) {
+#define KERNEL_MAX_SIZE 12
+        char kernelMax[KERNEL_MAX_SIZE];
+        ssize_t actual = read(fd, kernelMax, sizeof(kernelMax));
+        if (actual >= 2 && kernelMax[actual-1] == '\n') {
+            sKernelMax = atoi(kernelMax);
+            if (sKernelMax >= MAX_CPU - 1) {
+                ALOGW("kernel_max %d but MAX_CPU %d", sKernelMax, MAX_CPU);
+                sKernelMax = MAX_CPU;
+            } else if (sKernelMax < 0) {
+                ALOGW("kernel_max invalid %d", sKernelMax);
+                sKernelMax = 1;
+            } else {
+                ++sKernelMax;
+                ALOGV("number of CPUs %d", sKernelMax);
+            }
+        } else {
+            ALOGW("Can't read number of CPUs");
+        }
+        (void) close(fd);
+    } else {
+        ALOGW("Can't open number of CPUs");
+    }
+
+    // open fd to each frequency per CPU
+#define FREQ_SIZE 64
+    char freq_path[FREQ_SIZE];
+#define FREQ_DIGIT 27
+    COMPILE_TIME_ASSERT_FUNCTION_SCOPE(MAX_CPU <= 10);
+    strlcpy(freq_path, "/sys/devices/system/cpu/cpu?/cpufreq/scaling_cur_freq", sizeof(freq_path));
+    int i;
+    for (i = 0; i < MAX_CPU; ++i) {
+        sScalingFds[i] = -1;
+    }
+    for (i = 0; i < sKernelMax; ++i) {
+        freq_path[FREQ_DIGIT] = i + '0';
+        fd = open(freq_path, O_RDONLY);
+        if (fd >= 0) {
+            // keep this fd until process exit
+            sScalingFds[i] = fd;
+        } else {
+            ALOGW("Can't open CPU %d", i);
+        }
+    }
+}
+
+uint32_t ThreadCpuUsage::getCpukHz(int cpuNum)
+{
+    if (cpuNum < 0 || cpuNum >= MAX_CPU) {
+        ALOGW("getCpukHz called with invalid CPU %d", cpuNum);
+        return 0;
+    }
+    int fd = sScalingFds[cpuNum];
+    if (fd < 0) {
+        ALOGW("getCpukHz called for unopened CPU %d", cpuNum);
+        return 0;
+    }
+#define KHZ_SIZE 12
+    char kHz[KHZ_SIZE];   // kHz base 10
+    ssize_t actual = pread(fd, kHz, sizeof(kHz), (off_t) 0);
+    uint32_t ret;
+    if (actual >= 2 && kHz[actual-1] == '\n') {
+        ret = atoi(kHz);
+    } else {
+        ret = 0;
+    }
+    if (ret != mCurrentkHz[cpuNum]) {
+        if (ret > 0) {
+            ALOGV("CPU %d frequency %u kHz", cpuNum, ret);
+        } else {
+            ALOGW("Can't read CPU %d frequency", cpuNum);
+        }
+        mCurrentkHz[cpuNum] = ret;
+    }
+    return ret;
+}
+
+}   // namespace android
diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index bfa4a49..e3dbe01 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -57,9 +57,13 @@
 
 #include <audio_utils/primitives.h>
 
-#include <cpustats/ThreadCpuUsage.h>
 #include <powermanager/PowerManager.h>
+
 // #define DEBUG_CPU_USAGE 10  // log statistics every n wall clock seconds
+#ifdef DEBUG_CPU_USAGE
+#include <cpustats/CentralTendencyStatistics.h>
+#include <cpustats/ThreadCpuUsage.h>
+#endif
 
 #include <common_time/cc_helper.h>
 #include <common_time/local_clock.h>
@@ -1939,30 +1943,83 @@
 
 class CpuStats {
 public:
-    void sample();
+    CpuStats();
+    void sample(const String8 &title);
 #ifdef DEBUG_CPU_USAGE
 private:
-    ThreadCpuUsage mCpu;
+    ThreadCpuUsage mCpuUsage;           // instantaneous thread CPU usage in wall clock ns
+    CentralTendencyStatistics mWcStats; // statistics on thread CPU usage in wall clock ns
+
+    CentralTendencyStatistics mHzStats; // statistics on thread CPU usage in cycles
+
+    int mCpuNum;                        // thread's current CPU number
+    int mCpukHz;                        // frequency of thread's current CPU in kHz
 #endif
 };
 
-void CpuStats::sample() {
+CpuStats::CpuStats()
 #ifdef DEBUG_CPU_USAGE
-    const CentralTendencyStatistics& stats = mCpu.statistics();
-    mCpu.sampleAndEnable();
-    unsigned n = stats.n();
-    // mCpu.elapsed() is expensive, so don't call it every loop
+    : mCpuNum(-1), mCpukHz(-1)
+#endif
+{
+}
+
+void CpuStats::sample(const String8 &title) {
+#ifdef DEBUG_CPU_USAGE
+    // get current thread's delta CPU time in wall clock ns
+    double wcNs;
+    bool valid = mCpuUsage.sampleAndEnable(wcNs);
+
+    // record sample for wall clock statistics
+    if (valid) {
+        mWcStats.sample(wcNs);
+    }
+
+    // get the current CPU number
+    int cpuNum = sched_getcpu();
+
+    // get the current CPU frequency in kHz
+    int cpukHz = mCpuUsage.getCpukHz(cpuNum);
+
+    // check if either CPU number or frequency changed
+    if (cpuNum != mCpuNum || cpukHz != mCpukHz) {
+        mCpuNum = cpuNum;
+        mCpukHz = cpukHz;
+        // ignore sample for purposes of cycles
+        valid = false;
+    }
+
+    // if no change in CPU number or frequency, then record sample for cycle statistics
+    if (valid && mCpukHz > 0) {
+        double cycles = wcNs * cpukHz * 0.000001;
+        mHzStats.sample(cycles);
+    }
+
+    unsigned n = mWcStats.n();
+    // mCpuUsage.elapsed() is expensive, so don't call it every loop
     if ((n & 127) == 1) {
-        long long elapsed = mCpu.elapsed();
+        long long elapsed = mCpuUsage.elapsed();
         if (elapsed >= DEBUG_CPU_USAGE * 1000000000LL) {
             double perLoop = elapsed / (double) n;
             double perLoop100 = perLoop * 0.01;
-            double mean = stats.mean();
-            double stddev = stats.stddev();
-            double minimum = stats.minimum();
-            double maximum = stats.maximum();
-            mCpu.resetStatistics();
-            ALOGI("CPU usage over past %.1f secs (%u mixer loops at %.1f mean ms per loop):\n  us per mix loop: mean=%.0f stddev=%.0f min=%.0f max=%.0f\n  %% of wall: mean=%.1f stddev=%.1f min=%.1f max=%.1f",
+            double perLoop1k = perLoop * 0.001;
+            double mean = mWcStats.mean();
+            double stddev = mWcStats.stddev();
+            double minimum = mWcStats.minimum();
+            double maximum = mWcStats.maximum();
+            double meanCycles = mHzStats.mean();
+            double stddevCycles = mHzStats.stddev();
+            double minCycles = mHzStats.minimum();
+            double maxCycles = mHzStats.maximum();
+            mCpuUsage.resetElapsed();
+            mWcStats.reset();
+            mHzStats.reset();
+            ALOGD("CPU usage for %s over past %.1f secs\n"
+                "  (%u mixer loops at %.1f mean ms per loop):\n"
+                "  us per mix loop: mean=%.0f stddev=%.0f min=%.0f max=%.0f\n"
+                "  %% of wall: mean=%.1f stddev=%.1f min=%.1f max=%.1f\n"
+                "  MHz: mean=%.1f, stddev=%.1f, min=%.1f max=%.1f",
+                    title.string(),
                     elapsed * .000000001, n, perLoop * .000001,
                     mean * .001,
                     stddev * .001,
@@ -1971,7 +2028,12 @@
                     mean / perLoop100,
                     stddev / perLoop100,
                     minimum / perLoop100,
-                    maximum / perLoop100);
+                    maximum / perLoop100,
+                    meanCycles / perLoop1k,
+                    stddevCycles / perLoop1k,
+                    minCycles / perLoop1k,
+                    maxCycles / perLoop1k);
+
         }
     }
 #endif
@@ -2017,16 +2079,14 @@
     sleepTimeShift = 0;
 }
 
-    // MIXER
     CpuStats cpuStats;
+    const String8 myName(String8::format("thread %p type %d TID %d", this, mType, gettid()));
 
     acquireWakeLock();
 
     while (!exitPending())
     {
-if (mType == MIXER) {
-        cpuStats.sample();
-}
+        cpuStats.sample(myName);
 
         Vector< sp<EffectChain> > effectChains;
 
@@ -2063,9 +2123,9 @@
 
                     releaseWakeLock_l();
                     // wait until we have something to do...
-                    ALOGV("Thread %p type %d TID %d going to sleep", this, mType, gettid());
+                    ALOGV("%s going to sleep", myName.string());
                     mWaitWorkCV.wait(mLock);
-                    ALOGV("Thread %p type %d TID %d waking up", this, mType, gettid());
+                    ALOGV("%s waking up", myName.string());
                     acquireWakeLock_l();
 
                     mPrevMixerStatus = MIXER_IDLE;