Update CpuInfoReader to compute normalized available CPU frequency.

- Guard against reading CpuInfos too frequently.
- Implement dump logic in CpuInfoReader.
- Guard against zero time value in the time_in_state file.

Test: atest CpuInfoReaderTest
Bug: 242722241
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:67bc88121775785907a3aebd87db7c4bdef5fff9)
Merged-In: I9fc109c43fe0bd5f1d16135ad3167325ae502e15
Change-Id: I9fc109c43fe0bd5f1d16135ad3167325ae502e15

2 files changed, 190 insertions, 48 deletions

diff --git a/services/core/java/com/android/server/cpu/CpuInfoReader.java b/services/core/java/com/android/server/cpu/CpuInfoReader.java
index ca97a9847b39..ce68edbb9fa1 100644
--- a/services/core/java/com/android/server/cpu/CpuInfoReader.java
+++ b/services/core/java/com/android/server/cpu/CpuInfoReader.java
@@ -21,8 +21,10 @@ import static com.android.server.cpu.CpuMonitorService.TAG;
 
 import android.annotation.IntDef;
 import android.annotation.Nullable;
+import android.os.SystemClock;
 import android.system.Os;
 import android.system.OsConstants;
+import android.util.IndentingPrintWriter;
 import android.util.IntArray;
 import android.util.LongSparseLongArray;
 import android.util.SparseArray;
@@ -50,6 +52,9 @@ public final class CpuInfoReader {
     private static final String POLICY_DIR_PREFIX = "policy";
     private static final String RELATED_CPUS_FILE = "related_cpus";
     private static final String AFFECTED_CPUS_FILE = "affected_cpus";
+    // TODO(b/263154344): Avoid reading from cpuinfo_cur_freq because non-root users don't have
+    //  read permission for this file. The file permissions are set by the Kernel. Instead, read
+    //  the current frequency only from scaling_cur_freq.
     private static final String CUR_CPUFREQ_FILE = "cpuinfo_cur_freq";
     private static final String MAX_CPUFREQ_FILE = "cpuinfo_max_freq";
     private static final String CUR_SCALING_FREQ_FILE = "scaling_cur_freq";
@@ -70,16 +75,18 @@ public final class CpuInfoReader {
     private static final Pattern TIME_IN_STATE_PATTERN =
             Pattern.compile("(?<freqKHz>[0-9]+)\\s(?<time>[0-9]+)");
     private static final long MILLIS_PER_CLOCK_TICK = 1000L / Os.sysconf(OsConstants._SC_CLK_TCK);
+    private static final long MIN_READ_INTERVAL_MILLISECONDS = 500;
 
     @Retention(RetentionPolicy.SOURCE)
     @IntDef(prefix = {"FLAG_CPUSET_CATEGORY_"}, flag = true, value = {
             FLAG_CPUSET_CATEGORY_TOP_APP,
             FLAG_CPUSET_CATEGORY_BACKGROUND
     })
-    private @interface CpusetCategory{}
+    /** package **/ @interface CpusetCategory{}
 
     // TODO(b/242722241): Protect updatable variables with a local lock.
     private final File mCpusetDir;
+    private final long mMinReadIntervalMillis;
     private final SparseIntArray mCpusetCategoriesByCpus = new SparseIntArray();
     private final SparseArray<File> mCpuFreqPolicyDirsById = new SparseArray<>();
     private final SparseArray<StaticPolicyInfo> mStaticPolicyInfoById = new SparseArray<>();
@@ -90,16 +97,20 @@ public final class CpuInfoReader {
     private SparseArray<CpuUsageStats> mCumulativeCpuUsageStats = new SparseArray<>();
     private boolean mIsEnabled;
     private boolean mHasTimeInStateFile;
+    private long mLastReadUptimeMillis;
+    private SparseArray<CpuInfo> mLastReadCpuInfos;
 
     public CpuInfoReader() {
-        this(new File(CPUSET_DIR_PATH), new File(CPUFREQ_DIR_PATH), new File(PROC_STAT_FILE_PATH));
+        this(new File(CPUSET_DIR_PATH), new File(CPUFREQ_DIR_PATH), new File(PROC_STAT_FILE_PATH),
+                MIN_READ_INTERVAL_MILLISECONDS);
     }
 
     @VisibleForTesting
-    CpuInfoReader(File cpusetDir, File cpuFreqDir, File procStatFile) {
+    CpuInfoReader(File cpusetDir, File cpuFreqDir, File procStatFile, long minReadIntervalMillis) {
         mCpusetDir = cpusetDir;
         mCpuFreqDir = cpuFreqDir;
         mProcStatFile = procStatFile;
+        mMinReadIntervalMillis = minReadIntervalMillis;
     }
 
     /**
@@ -167,6 +178,16 @@ public final class CpuInfoReader {
         if (!mIsEnabled) {
             return null;
         }
+        long uptimeMillis = SystemClock.uptimeMillis();
+        if (mLastReadUptimeMillis > 0
+                && uptimeMillis - mLastReadUptimeMillis < mMinReadIntervalMillis) {
+            Slogf.w(TAG, "Skipping reading from device and returning the last read CpuInfos. "
+                    + "Last read was %d ms ago, min read interval is %d ms",
+                    uptimeMillis - mLastReadUptimeMillis, mMinReadIntervalMillis);
+            return mLastReadCpuInfos;
+        }
+        mLastReadUptimeMillis = uptimeMillis;
+        mLastReadCpuInfos = null;
         SparseArray<CpuUsageStats> cpuUsageStatsByCpus = readLatestCpuUsageStats();
         if (cpuUsageStatsByCpus == null || cpuUsageStatsByCpus.size() == 0) {
             Slogf.e(TAG, "Failed to read latest CPU usage stats");
@@ -202,6 +223,12 @@ public final class CpuInfoReader {
                         + " policy ID %d", policyId);
                 continue;
             }
+            if (curFreqKHz > maxFreqKHz) {
+                Slogf.w(TAG, "Current CPU frequency (%d) is greater than maximum CPU frequency"
+                        + " (%d) for policy ID (%d). Skipping CPU frequency policy", curFreqKHz,
+                        maxFreqKHz, policyId);
+                continue;
+            }
             for (int coreIdx = 0; coreIdx < staticPolicyInfo.relatedCpuCores.size(); coreIdx++) {
                 int relatedCpuCore = staticPolicyInfo.relatedCpuCores.get(coreIdx);
                 CpuInfo prevCpuInfo = cpuInfoByCpus.get(relatedCpuCore);
@@ -241,9 +268,73 @@ public final class CpuInfoReader {
                 }
             }
         }
+        mLastReadCpuInfos = cpuInfoByCpus;
         return cpuInfoByCpus;
     }
 
+    /** Dumps the current state. */
+    public void dump(IndentingPrintWriter writer) {
+        writer.printf("*%s*\n", getClass().getSimpleName());
+        writer.increaseIndent();    // Add intend for the outermost block.
+
+        writer.printf("mCpusetDir = %s\n", mCpusetDir.getAbsolutePath());
+        writer.printf("mCpuFreqDir = %s\n", mCpuFreqDir.getAbsolutePath());
+        writer.printf("mProcStatFile = %s\n", mProcStatFile.getAbsolutePath());
+        writer.printf("mIsEnabled = %s\n", mIsEnabled);
+        writer.printf("mHasTimeInStateFile = %s\n", mHasTimeInStateFile);
+        writer.printf("mLastReadUptimeMillis = %d\n", mLastReadUptimeMillis);
+        writer.printf("mMinReadIntervalMillis = %d\n", mMinReadIntervalMillis);
+
+        writer.printf("Cpuset categories by CPU core:\n");
+        writer.increaseIndent();
+        for (int i = 0; i < mCpusetCategoriesByCpus.size(); i++) {
+            writer.printf("CPU core id = %d, %s\n", mCpusetCategoriesByCpus.keyAt(i),
+                    toCpusetCategoriesStr(mCpusetCategoriesByCpus.valueAt(i)));
+        }
+        writer.decreaseIndent();
+
+        writer.println("Cpu frequency policy directories by policy id:");
+        writer.increaseIndent();
+        for (int i = 0; i < mCpuFreqPolicyDirsById.size(); i++) {
+            writer.printf("Policy id = %d, Dir = %s\n", mCpuFreqPolicyDirsById.keyAt(i),
+                    mCpuFreqPolicyDirsById.valueAt(i));
+        }
+        writer.decreaseIndent();
+
+        writer.println("Static cpu frequency policy infos by policy id:");
+        writer.increaseIndent();
+        for (int i = 0; i < mStaticPolicyInfoById.size(); i++) {
+            writer.printf("Policy id = %d, %s\n", mStaticPolicyInfoById.keyAt(i),
+                    mStaticPolicyInfoById.valueAt(i));
+        }
+        writer.decreaseIndent();
+
+        writer.println("Cpu time in frequency state by policy id:");
+        writer.increaseIndent();
+        for (int i = 0; i < mTimeInStateByPolicyId.size(); i++) {
+            writer.printf("Policy id = %d, Time(millis) in state by CPU frequency(KHz) = %s\n",
+                    mTimeInStateByPolicyId.keyAt(i), mTimeInStateByPolicyId.valueAt(i));
+        }
+        writer.decreaseIndent();
+
+        writer.println("Last read CPU infos:");
+        writer.increaseIndent();
+        for (int i = 0; i < mLastReadCpuInfos.size(); i++) {
+            writer.printf("%s\n", mLastReadCpuInfos.valueAt(i));
+        }
+        writer.decreaseIndent();
+
+        writer.println("Latest cumulative CPU usage stats by CPU core:");
+        writer.increaseIndent();
+        for (int i = 0; i < mCumulativeCpuUsageStats.size(); i++) {
+            writer.printf("CPU core id = %d, %s\n", mCumulativeCpuUsageStats.keyAt(i),
+                    mCumulativeCpuUsageStats.valueAt(i));
+        }
+        writer.decreaseIndent();
+
+        writer.decreaseIndent();    // Remove intend for the outermost block.
+    }
+
     /**
      * Sets the CPU frequency for testing.
      *
@@ -496,6 +587,9 @@ public final class CpuInfoReader {
         for (int i = 0; i < timeInState.size(); i++) {
             totalTimeInState += timeInState.valueAt(i);
         }
+        if (totalTimeInState == 0) {
+            return CpuInfo.MISSING_FREQUENCY;
+        }
         double avgFreqKHz = 0;
         for (int i = 0; i < timeInState.size(); i++) {
             avgFreqKHz += (timeInState.keyAt(i) * timeInState.valueAt(i)) / totalTimeInState;
@@ -624,16 +718,29 @@ public final class CpuInfoReader {
         @CpusetCategory
         public final int cpusetCategories;
         public final boolean isOnline;
+        public final long maxCpuFreqKHz;
         // Values in the below fields may be missing when a CPU core is offline.
         public final long curCpuFreqKHz;
-        public final long maxCpuFreqKHz;
         public final long avgTimeInStateCpuFreqKHz;
         @Nullable
         public final CpuUsageStats latestCpuUsageStats;
 
+        private long mNormalizedAvailableCpuFreqKHz;
+
         CpuInfo(int cpuCore, @CpusetCategory int cpusetCategories, boolean isOnline,
                 long curCpuFreqKHz, long maxCpuFreqKHz, long avgTimeInStateCpuFreqKHz,
                 CpuUsageStats latestCpuUsageStats) {
+            this(cpuCore, cpusetCategories, isOnline, curCpuFreqKHz, maxCpuFreqKHz,
+                    avgTimeInStateCpuFreqKHz, /* normalizedAvailableCpuFreqKHz= */ 0,
+                    latestCpuUsageStats);
+            this.mNormalizedAvailableCpuFreqKHz = computeNormalizedAvailableCpuFreqKHz();
+        }
+
+        // Should be used only for testing.
+        @VisibleForTesting
+        CpuInfo(int cpuCore, @CpusetCategory int cpusetCategories, boolean isOnline,
+                long curCpuFreqKHz, long maxCpuFreqKHz, long avgTimeInStateCpuFreqKHz,
+                long normalizedAvailableCpuFreqKHz, CpuUsageStats latestCpuUsageStats) {
             this.cpuCore = cpuCore;
             this.cpusetCategories = cpusetCategories;
             this.isOnline = isOnline;
@@ -641,6 +748,11 @@ public final class CpuInfoReader {
             this.maxCpuFreqKHz = maxCpuFreqKHz;
             this.avgTimeInStateCpuFreqKHz = avgTimeInStateCpuFreqKHz;
             this.latestCpuUsageStats = latestCpuUsageStats;
+            this.mNormalizedAvailableCpuFreqKHz = normalizedAvailableCpuFreqKHz;
+        }
+
+        public long getNormalizedAvailableCpuFreqKHz() {
+            return mNormalizedAvailableCpuFreqKHz;
         }
 
         @Override
@@ -657,6 +769,8 @@ public final class CpuInfoReader {
                     .append(avgTimeInStateCpuFreqKHz == MISSING_FREQUENCY ? "missing"
                             : avgTimeInStateCpuFreqKHz)
                     .append(", latestCpuUsageStats = ").append(latestCpuUsageStats)
+                    .append(", mNormalizedAvailableCpuFreqKHz = ")
+                    .append(mNormalizedAvailableCpuFreqKHz)
                     .append(" }").toString();
         }
 
@@ -673,13 +787,32 @@ public final class CpuInfoReader {
                     && isOnline == other.isOnline  && curCpuFreqKHz == other.curCpuFreqKHz
                     && maxCpuFreqKHz == other.maxCpuFreqKHz
                     && avgTimeInStateCpuFreqKHz == other.avgTimeInStateCpuFreqKHz
-                    && latestCpuUsageStats.equals(other.latestCpuUsageStats);
+                    && latestCpuUsageStats.equals(other.latestCpuUsageStats)
+                    && mNormalizedAvailableCpuFreqKHz == other.mNormalizedAvailableCpuFreqKHz;
         }
 
         @Override
         public int hashCode() {
             return Objects.hash(cpuCore, cpusetCategories, isOnline, curCpuFreqKHz, maxCpuFreqKHz,
-                    avgTimeInStateCpuFreqKHz, latestCpuUsageStats);
+                    avgTimeInStateCpuFreqKHz, latestCpuUsageStats, mNormalizedAvailableCpuFreqKHz);
+        }
+
+        private long computeNormalizedAvailableCpuFreqKHz() {
+            if (!isOnline) {
+                return MISSING_FREQUENCY;
+            }
+            long totalTimeMillis = latestCpuUsageStats.getTotalTimeMillis();
+            if (totalTimeMillis == 0) {
+                Slogf.wtf(TAG, "Total CPU time millis is 0. This shouldn't happen unless stats are"
+                        + " polled too frequently");
+                return MISSING_FREQUENCY;
+            }
+            double nonIdlePercent = 100.0 * (totalTimeMillis
+                    - (double) latestCpuUsageStats.idleTimeMillis) / totalTimeMillis;
+            long curFreqKHz = avgTimeInStateCpuFreqKHz == MISSING_FREQUENCY
+                    ? curCpuFreqKHz : avgTimeInStateCpuFreqKHz;
+            double availablePercent = 100.0 - (nonIdlePercent * curFreqKHz / maxCpuFreqKHz);
+            return (long) ((availablePercent * maxCpuFreqKHz) / 100.0);
         }
     }
 
@@ -712,7 +845,7 @@ public final class CpuInfoReader {
             this.guestNiceTimeMillis = guestNiceTimeMillis;
         }
 
-        public long getTotalTime() {
+        public long getTotalTimeMillis() {
             return userTimeMillis + niceTimeMillis + systemTimeMillis + idleTimeMillis
                     + iowaitTimeMillis + irqTimeMillis + softirqTimeMillis + stealTimeMillis
                     + guestTimeMillis + guestNiceTimeMillis;
@@ -796,8 +929,8 @@ public final class CpuInfoReader {
 
         @Override
         public String toString() {
-            return "FrequencyPair{cpuFreqKHz=" + cpuFreqKHz + ", scalingFreqKHz=" + scalingFreqKHz
-                    + '}';
+            return "FrequencyPair{cpuFreqKHz = " + cpuFreqKHz + ", scalingFreqKHz = "
+                    + scalingFreqKHz + '}';
         }
     }
 
@@ -812,7 +945,7 @@ public final class CpuInfoReader {
 
         @Override
         public String toString() {
-            return "StaticPolicyInfo{maxCpuFreqPair=" + maxCpuFreqPair + ", relatedCpuCores="
+            return "StaticPolicyInfo{maxCpuFreqPair = " + maxCpuFreqPair + ", relatedCpuCores = "
                     + relatedCpuCores + '}';
         }
     }
@@ -831,9 +964,9 @@ public final class CpuInfoReader {
 
         @Override
         public String toString() {
-            return "DynamicPolicyInfo{curCpuFreqPair=" + curCpuFreqPair
-                    + ", avgTimeInStateCpuFreqKHz=" + avgTimeInStateCpuFreqKHz
-                    + ", affectedCpuCores=" + affectedCpuCores + '}';
+            return "DynamicPolicyInfo{curCpuFreqPair = " + curCpuFreqPair
+                    + ", avgTimeInStateCpuFreqKHz = " + avgTimeInStateCpuFreqKHz
+                    + ", affectedCpuCores = " + affectedCpuCores + '}';
         }
     }
 }
diff --git a/services/tests/mockingservicestests/src/com/android/server/cpu/CpuInfoReaderTest.java b/services/tests/mockingservicestests/src/com/android/server/cpu/CpuInfoReaderTest.java
index b21478753301..04f6f8b2e9f0 100644
--- a/services/tests/mockingservicestests/src/com/android/server/cpu/CpuInfoReaderTest.java
+++ b/services/tests/mockingservicestests/src/com/android/server/cpu/CpuInfoReaderTest.java
@@ -92,6 +92,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(0, new CpuInfoReader.CpuInfo(/* cpuCore= */ 0,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 1_230_000,
                 /* maxCpuFreqKHz= */ 2_500_000, /* avgTimeInStateCpuFreqKHz= */ 488_095,
+                /* normalizedAvailableCpuFreqKHz= */ 2_402_267,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 32_249_610,
                         /* niceTimeMillis= */ 7_950_930, /* systemTimeMillis= */ 52_227_050,
                         /* idleTimeMillis= */ 409_036_950, /* iowaitTimeMillis= */ 1_322_810,
@@ -101,6 +102,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(1, new CpuInfoReader.CpuInfo(/* cpuCore= */ 1,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 1_450_000,
                 /* maxCpuFreqKHz= */ 2_800_000, /* avgTimeInStateCpuFreqKHz= */ 502_380,
+                /* normalizedAvailableCpuFreqKHz= */ 2_693_525,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 28_949_280,
                         /* niceTimeMillis= */ 7_799_450, /* systemTimeMillis= */ 54_004_020,
                         /* idleTimeMillis= */ 402_707_120, /* iowaitTimeMillis= */ 1_186_960,
@@ -111,6 +113,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
                 FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
                 /* isOnline= */ true, /* curCpuFreqKHz= */ 1_000_000,
                 /* maxCpuFreqKHz= */ 2_000_000, /* avgTimeInStateCpuFreqKHz= */ 464_285,
+                /* normalizedAvailableCpuFreqKHz= */ 1_901_608,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 28_959_280,
                         /* niceTimeMillis= */ 7_789_450, /* systemTimeMillis= */ 54_014_020,
                         /* idleTimeMillis= */ 402_717_120, /* iowaitTimeMillis= */ 1_166_960,
@@ -121,6 +124,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
                 FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
                 /* isOnline= */ true, /* curCpuFreqKHz= */ 1_000_000,
                 /* maxCpuFreqKHz= */ 2_000_000, /* avgTimeInStateCpuFreqKHz= */ 464_285,
+                /* normalizedAvailableCpuFreqKHz= */ 1_907_125,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 32_349_610,
                         /* niceTimeMillis= */ 7_850_930, /* systemTimeMillis= */ 52_127_050,
                         /* idleTimeMillis= */ 409_136_950, /* iowaitTimeMillis= */ 1_332_810,
@@ -139,6 +143,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(0, new CpuInfoReader.CpuInfo(/* cpuCore= */ 0,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 1_000_000,
                 /* maxCpuFreqKHz= */ 2_500_000, /* avgTimeInStateCpuFreqKHz= */ 419_354,
+                /* normalizedAvailableCpuFreqKHz= */ 2_425_919,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 10_000_000,
                         /* niceTimeMillis= */ 1_000_000, /* systemTimeMillis= */ 10_000_000,
                         /* idleTimeMillis= */ 110_000_000, /* iowaitTimeMillis= */ 1_100_000,
@@ -148,6 +153,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(1, new CpuInfoReader.CpuInfo(/* cpuCore= */ 1,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 2_800_000,
                 /* maxCpuFreqKHz= */ 2_800_000, /* avgTimeInStateCpuFreqKHz= */ 429_032,
+                /* normalizedAvailableCpuFreqKHz= */ 2_403_009,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 900_000,
                         /* niceTimeMillis= */ 1_000_000, /* systemTimeMillis= */ 10_000_000,
                         /* idleTimeMillis= */ 1_000_000, /* iowaitTimeMillis= */ 90_000,
@@ -158,6 +164,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
                 FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
                 /* isOnline= */ true, /* curCpuFreqKHz= */ 2_000_000,
                 /* maxCpuFreqKHz= */ 2_000_000, /* avgTimeInStateCpuFreqKHz= */ 403_225,
+                /* normalizedAvailableCpuFreqKHz= */ 1_688_209,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 10_000_000,
                         /* niceTimeMillis= */ 2_000_000, /* systemTimeMillis= */ 0,
                         /* idleTimeMillis= */ 10_000_000, /* iowaitTimeMillis= */ 1_000_000,
@@ -168,6 +175,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
                 FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
                 /* isOnline= */ false, /* curCpuFreqKHz= */ MISSING_FREQUENCY,
                 /* maxCpuFreqKHz= */ 2_000_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
+                /* normalizedAvailableCpuFreqKHz= */ MISSING_FREQUENCY,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 2_000_000,
                         /* niceTimeMillis= */ 1_000_000, /* systemTimeMillis= */ 1_000_000,
                         /* idleTimeMillis= */ 100_000, /* iowaitTimeMillis= */ 100_000,
@@ -189,6 +197,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(0, new CpuInfoReader.CpuInfo(/* cpuCore= */ 0,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 1_230_000,
                 /* maxCpuFreqKHz= */ 2_500_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
+                /* normalizedAvailableCpuFreqKHz= */ 2_253_713,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 32_249_610,
                         /* niceTimeMillis= */ 7_950_930, /* systemTimeMillis= */ 52_227_050,
                         /* idleTimeMillis= */ 409_036_950, /* iowaitTimeMillis= */ 1_322_810,
@@ -198,6 +207,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(1, new CpuInfoReader.CpuInfo(/* cpuCore= */ 1,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 1_450_000,
                 /* maxCpuFreqKHz= */ 2_800_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
+                /* normalizedAvailableCpuFreqKHz= */ 2_492_687,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 28_949_280,
                         /* niceTimeMillis= */ 7_799_450, /* systemTimeMillis= */ 54_004_020,
                         /* idleTimeMillis= */ 402_707_120, /* iowaitTimeMillis= */ 1_186_960,
@@ -208,6 +218,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
                 FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
                 /* isOnline= */ true, /* curCpuFreqKHz= */ 1_000_000,
                 /* maxCpuFreqKHz= */ 2_000_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
+                /* normalizedAvailableCpuFreqKHz= */ 1_788_079,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 28_959_280,
                         /* niceTimeMillis= */ 7_789_450, /* systemTimeMillis= */ 54_014_020,
                         /* idleTimeMillis= */ 402_717_120, /* iowaitTimeMillis= */ 1_166_960,
@@ -218,6 +229,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
                 FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
                 /* isOnline= */ true, /* curCpuFreqKHz= */ 1_000_000,
                 /* maxCpuFreqKHz= */ 2_000_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
+                /* normalizedAvailableCpuFreqKHz= */ 1_799_962,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 32_349_610,
                         /* niceTimeMillis= */ 7_850_930, /* systemTimeMillis= */ 52_127_050,
                         /* idleTimeMillis= */ 409_136_950, /* iowaitTimeMillis= */ 1_332_810,
@@ -237,6 +249,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(0, new CpuInfoReader.CpuInfo(/* cpuCore= */ 0,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 1_000_000,
                 /* maxCpuFreqKHz= */ 2_500_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
+                /* normalizedAvailableCpuFreqKHz= */ 2323347,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 10_000_000,
                         /* niceTimeMillis= */ 1_000_000, /* systemTimeMillis= */ 10_000_000,
                         /* idleTimeMillis= */ 110_000_000, /* iowaitTimeMillis= */ 1_100_000,
@@ -246,6 +259,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(1, new CpuInfoReader.CpuInfo(/* cpuCore= */ 1,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 2_800_000,
                 /* maxCpuFreqKHz= */ 2_800_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
+                /* normalizedAvailableCpuFreqKHz= */ 209111,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 900_000,
                         /* niceTimeMillis= */ 1_000_000, /* systemTimeMillis= */ 10_000_000,
                         /* idleTimeMillis= */ 1_000_000, /* iowaitTimeMillis= */ 90_000,
@@ -256,6 +270,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
                 FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
                 /* isOnline= */ true, /* curCpuFreqKHz= */ 2_000_000,
                 /* maxCpuFreqKHz= */ 2_000_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
+                /* normalizedAvailableCpuFreqKHz= */ 453514,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 10_000_000,
                         /* niceTimeMillis= */ 2_000_000, /* systemTimeMillis= */ 0,
                         /* idleTimeMillis= */ 10_000_000, /* iowaitTimeMillis= */ 1_000_000,
@@ -266,6 +281,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
                 FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
                 /* isOnline= */ true, /* curCpuFreqKHz= */ 2_000_000,
                 /* maxCpuFreqKHz= */ 2_000_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
+                /* normalizedAvailableCpuFreqKHz= */ 37728,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 2_000_000,
                         /* niceTimeMillis= */ 1_000_000, /* systemTimeMillis= */ 1_000_000,
                         /* idleTimeMillis= */ 100_000, /* iowaitTimeMillis= */ 100_000,
@@ -323,38 +339,8 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
 
         SparseArray<CpuInfoReader.CpuInfo> actualCpuInfos = cpuInfoReader.readCpuInfos();
         SparseArray<CpuInfoReader.CpuInfo> expectedCpuInfos = new SparseArray<>();
-        expectedCpuInfos.append(1, new CpuInfoReader.CpuInfo(/* cpuCore= */ 1,
-                FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 3_000_000,
-                /* maxCpuFreqKHz= */ 1_000_000, /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
-                new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 28_949_280,
-                        /* niceTimeMillis= */ 7_799_450, /* systemTimeMillis= */ 54_004_020,
-                        /* idleTimeMillis= */ 402_707_120, /* iowaitTimeMillis= */ 1_186_960,
-                        /* irqTimeMillis= */ 14_786_940, /* softirqTimeMillis= */ 1_498_130,
-                        /* stealTimeMillis= */ 78_780, /* guestTimeMillis= */ 0,
-                        /* guestNiceTimeMillis= */ 0)));
-        expectedCpuInfos.append(2, new CpuInfoReader.CpuInfo(/* cpuCore= */ 2,
-                FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
-                /* isOnline= */ true, /* curCpuFreqKHz= */ 9, /* maxCpuFreqKHz= */ 2,
-                /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
-                new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 28_959_280,
-                        /* niceTimeMillis= */ 7_789_450, /* systemTimeMillis= */ 54_014_020,
-                        /* idleTimeMillis= */ 402_717_120, /* iowaitTimeMillis= */ 1_166_960,
-                        /* irqTimeMillis= */ 14_796_940, /* softirqTimeMillis= */ 1_478_130,
-                        /* stealTimeMillis= */ 88_780, /* guestTimeMillis= */ 0,
-                        /* guestNiceTimeMillis= */ 0)));
-        expectedCpuInfos.append(3, new CpuInfoReader.CpuInfo(/* cpuCore= */ 3,
-                FLAG_CPUSET_CATEGORY_TOP_APP | FLAG_CPUSET_CATEGORY_BACKGROUND,
-                /* isOnline= */ true, /* curCpuFreqKHz= */ 9, /* maxCpuFreqKHz= */ 2,
-                /* avgTimeInStateCpuFreqKHz= */ MISSING_FREQUENCY,
-                new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 32_349_610,
-                        /* niceTimeMillis= */ 7_850_930, /* systemTimeMillis= */ 52_127_050,
-                        /* idleTimeMillis= */ 409_136_950, /* iowaitTimeMillis= */ 1_332_810,
-                        /* irqTimeMillis= */ 8_136_740, /* softirqTimeMillis= */ 438_970,
-                        /* stealTimeMillis= */ 71_950, /* guestTimeMillis= */ 0,
-                        /* guestNiceTimeMillis= */ 0)));
 
-        compareCpuInfos("CPU infos with corrupted CPU frequency", expectedCpuInfos,
-                actualCpuInfos);
+        compareCpuInfos("CPU infos with corrupted CPU frequency", expectedCpuInfos, actualCpuInfos);
     }
 
     @Test
@@ -368,6 +354,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(0, new CpuInfoReader.CpuInfo(/* cpuCore= */ 0,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 1_230_000,
                 /* maxCpuFreqKHz= */ 2_500_000, /* avgTimeInStateCpuFreqKHz= */ 488_095,
+                /* normalizedAvailableCpuFreqKHz= */ 2_402_267,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 32_249_610,
                         /* niceTimeMillis= */ 7_950_930, /* systemTimeMillis= */ 52_227_050,
                         /* idleTimeMillis= */ 409_036_950, /* iowaitTimeMillis= */ 1_322_810,
@@ -377,6 +364,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         expectedCpuInfos.append(1, new CpuInfoReader.CpuInfo(/* cpuCore= */ 1,
                 FLAG_CPUSET_CATEGORY_TOP_APP, /* isOnline= */ true, /* curCpuFreqKHz= */ 1_450_000,
                 /* maxCpuFreqKHz= */ 2_800_000, /* avgTimeInStateCpuFreqKHz= */ 502_380,
+                /* normalizedAvailableCpuFreqKHz= */ 2_693_525,
                 new CpuInfoReader.CpuUsageStats(/* userTimeMillis= */ 28_949_280,
                         /* niceTimeMillis= */ 7_799_450, /* systemTimeMillis= */ 54_004_020,
                         /* idleTimeMillis= */ 402_707_120, /* iowaitTimeMillis= */ 1_186_960,
@@ -393,7 +381,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         assertWithMessage("Make empty dir %s", emptyDir).that(emptyDir.mkdir()).isTrue();
         CpuInfoReader cpuInfoReader = new CpuInfoReader(emptyDir, getCacheFile(
                 VALID_CPUFREQ_WITH_TIME_IN_STATE_DIR),
-                getCacheFile(VALID_PROC_STAT));
+                getCacheFile(VALID_PROC_STAT), /* minReadIntervalMillis= */0);
 
         assertWithMessage("Init CPU reader info").that(cpuInfoReader.init()).isFalse();
 
@@ -406,7 +394,7 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         File emptyDir = getCacheFile(EMPTY_DIR);
         assertWithMessage("Make empty dir %s", emptyDir).that(emptyDir.mkdir()).isTrue();
         CpuInfoReader cpuInfoReader = new CpuInfoReader(getCacheFile(VALID_CPUSET_DIR), emptyDir,
-                getCacheFile(VALID_PROC_STAT));
+                getCacheFile(VALID_PROC_STAT), /* minReadIntervalMillis= */0);
 
         assertWithMessage("Init CPU reader info").that(cpuInfoReader.init()).isFalse();
 
@@ -420,12 +408,32 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
         assertWithMessage("Create empty file %s", emptyFile).that(emptyFile.createNewFile())
                 .isTrue();
         CpuInfoReader cpuInfoReader = new CpuInfoReader(getCacheFile(VALID_CPUSET_DIR),
-                getCacheFile(VALID_CPUFREQ_WITH_TIME_IN_STATE_DIR), getCacheFile(EMPTY_FILE));
+                getCacheFile(VALID_CPUFREQ_WITH_TIME_IN_STATE_DIR), getCacheFile(EMPTY_FILE),
+                /* minReadIntervalMillis= */0);
 
         assertWithMessage("Cpu infos with empty proc stat").that(cpuInfoReader.readCpuInfos())
                 .isNull();
     }
 
+    @Test
+    public void testReadingTooFrequentlyReturnsLastReadCpuInfos() throws Exception {
+        CpuInfoReader cpuInfoReader = new CpuInfoReader(getCacheFile(VALID_CPUSET_DIR),
+                getCacheFile(VALID_CPUFREQ_WITH_TIME_IN_STATE_DIR), getCacheFile(VALID_PROC_STAT),
+                /* minReadIntervalMillis= */ 60_000);
+        assertWithMessage("Initialize CPU info reader").that(cpuInfoReader.init()).isTrue();
+
+        SparseArray<CpuInfoReader.CpuInfo> firstCpuInfos = cpuInfoReader.readCpuInfos();
+        assertWithMessage("CPU infos first snapshot").that(firstCpuInfos).isNotNull();
+        assertWithMessage("CPU infos first snapshot size").that(firstCpuInfos.size())
+                .isGreaterThan(0);
+
+        SparseArray<CpuInfoReader.CpuInfo> secondCpuInfos = cpuInfoReader.readCpuInfos();
+        compareCpuInfos("CPU infos second snapshot", firstCpuInfos, secondCpuInfos);
+
+        SparseArray<CpuInfoReader.CpuInfo> thirdCpuInfos = cpuInfoReader.readCpuInfos();
+        compareCpuInfos("CPU infos third snapshot", firstCpuInfos, thirdCpuInfos);
+    }
+
     private void compareCpuInfos(String message,
             SparseArray<CpuInfoReader.CpuInfo> expected,
             SparseArray<CpuInfoReader.CpuInfo> actual) {
@@ -462,7 +470,8 @@ public final class CpuInfoReaderTest extends ExpectableTestCase {
 
     private static CpuInfoReader newCpuInfoReader(File cpusetDir, File cpuFreqDir,
             File procStatFile) {
-        CpuInfoReader cpuInfoReader = new CpuInfoReader(cpusetDir, cpuFreqDir, procStatFile);
+        CpuInfoReader cpuInfoReader = new CpuInfoReader(cpusetDir, cpuFreqDir, procStatFile,
+                /* minReadIntervalMillis= */ 0);
         assertWithMessage("Initialize CPU info reader").that(cpuInfoReader.init()).isTrue();
         return cpuInfoReader;
     }