Read cpusets and max CPU frequencies from devfs and sysfs.

Cpuset information and max CPU frequencies don't change after system bootup.
So, read them only once during init.

If these information are not available, the reader cannot generate CPU info.
So, disable the collector when these cannot be read.

Unit tests are added in one of the following changes.

Test: m
Bug: 217422127
Bug: 242722241

Change-Id: Icc201b65fdfe054da5258e8136750d518182d207
(cherry picked from commit 6a9c8e6063dc8503be23f6f9d94b5a04fafe0c09)

1 files changed, 226 insertions, 0 deletions

diff --git a/services/core/java/com/android/server/cpu/CpuInfoReader.java b/services/core/java/com/android/server/cpu/CpuInfoReader.java
new file mode 100644
index 000000000000..12ef88b1b67f
--- /dev/null
+++ b/services/core/java/com/android/server/cpu/CpuInfoReader.java
@@ -0,0 +1,226 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+package com.android.server.cpu;
+
+import android.annotation.IntDef;
+import android.util.SparseArray;
+import android.util.SparseIntArray;
+
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.server.utils.Slogf;
+
+import java.io.File;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.nio.file.Files;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/** Reader to read CPU information from proc and sys fs files exposed by the Kernel. */
+public final class CpuInfoReader {
+    static final String TAG = CpuInfoReader.class.getSimpleName();
+    static final int FLAG_CPUSET_CATEGORY_TOP_APP = 1 << 0;
+    static final int FLAG_CPUSET_CATEGORY_BACKGROUND = 1 << 1;
+
+    private static final String CPUFREQ_DIR_PATH = "/sys/devices/system/cpu/cpufreq";
+    private static final String POLICY_DIR_PREFIX = "policy";
+    private static final String RELATED_CPUS_FILE = "related_cpus";
+    private static final String MAX_CPUFREQ_FILE = "cpuinfo_max_freq";
+    private static final String MAX_SCALING_FREQ_FILE = "scaling_max_freq";
+    private static final String CPUSET_DIR_PATH = "/dev/cpuset";
+    private static final String CPUSET_TOP_APP_DIR = "top-app";
+    private static final String CPUSET_BACKGROUND_DIR = "background";
+    private static final String CPUS_FILE = "cpus";
+    private static final String PROC_STAT_FILE_PATH = "/proc/stat";
+
+    @Retention(RetentionPolicy.SOURCE)
+    @IntDef(prefix = {"FLAG_CPUSET_CATEGORY_"}, flag = true, value = {
+            FLAG_CPUSET_CATEGORY_TOP_APP,
+            FLAG_CPUSET_CATEGORY_BACKGROUND
+    })
+    private @interface CpusetCategory{}
+
+    private final File mCpusetDir;
+    private final File mCpuFreqDir;
+    private final File mProcStatFile;
+    private final SparseIntArray mCpusetCategoriesByCpus = new SparseIntArray();
+    private final SparseArray<Long> mMaxCpuFrequenciesByCpus = new SparseArray<>();
+
+    private File[] mCpuFreqPolicyDirs;
+
+    public CpuInfoReader() {
+        this(new File(CPUSET_DIR_PATH), new File(CPUFREQ_DIR_PATH), new File(PROC_STAT_FILE_PATH));
+    }
+
+    @VisibleForTesting
+    CpuInfoReader(File cpusetDir, File cpuFreqDir, File procStatFile) {
+        mCpusetDir = cpusetDir;
+        mCpuFreqDir = cpuFreqDir;
+        mProcStatFile = procStatFile;
+    }
+
+    /** Inits CpuInfoReader and returns a boolean to indicate whether the reader is enabled. */
+    public boolean init() {
+        mCpuFreqPolicyDirs = mCpuFreqDir.listFiles(
+                file -> file.isDirectory() && file.getName().startsWith(POLICY_DIR_PREFIX));
+        if (mCpuFreqPolicyDirs == null || mCpuFreqPolicyDirs.length == 0) {
+            Slogf.w(TAG, "Missing CPU frequency policy directories at %s",
+                    mCpuFreqDir.getAbsolutePath());
+            return false;
+        }
+        if (!mProcStatFile.exists()) {
+            Slogf.e(TAG, "Missing proc stat file at %s", mProcStatFile.getAbsolutePath());
+            return false;
+        }
+        readCpusetCategories();
+        if (mCpusetCategoriesByCpus.size() == 0) {
+            Slogf.e(TAG, "Failed to read cpuset information read from %s",
+                    mCpusetDir.getAbsolutePath());
+            return false;
+        }
+        readMaxCpuFrequencies();
+        if (mMaxCpuFrequenciesByCpus.size() == 0) {
+            Slogf.e(TAG, "Failed to read max CPU frequencies from policy directories at %s",
+                    mCpuFreqDir.getAbsolutePath());
+            return false;
+        }
+        return true;
+    }
+
+    private void readCpusetCategories() {
+        File[] cpusetDirs = mCpusetDir.listFiles(File::isDirectory);
+        if (cpusetDirs == null) {
+            Slogf.e(TAG, "Missing cpuset directories at %s", mCpusetDir.getAbsolutePath());
+            return;
+        }
+        for (int i = 0; i < cpusetDirs.length; i++) {
+            File dir = cpusetDirs[i];
+            @CpusetCategory int cpusetCategory;
+            switch (dir.getName()) {
+                case CPUSET_TOP_APP_DIR:
+                    cpusetCategory = FLAG_CPUSET_CATEGORY_TOP_APP;
+                    break;
+                case CPUSET_BACKGROUND_DIR:
+                    cpusetCategory = FLAG_CPUSET_CATEGORY_BACKGROUND;
+                    break;
+                default:
+                    continue;
+            }
+            File cpuCoresFile = new File(dir.getPath(), CPUS_FILE);
+            List<Integer> cpuCores = readCpuCores(cpuCoresFile);
+            if (cpuCores.isEmpty()) {
+                Slogf.e(TAG, "Failed to read CPU cores from %s", cpuCoresFile.getAbsolutePath());
+                continue;
+            }
+            for (int j = 0; j < cpuCores.size(); j++) {
+                int categories = mCpusetCategoriesByCpus.get(cpuCores.get(j));
+                categories |= cpusetCategory;
+                mCpusetCategoriesByCpus.append(cpuCores.get(j), categories);
+            }
+        }
+    }
+
+    private void readMaxCpuFrequencies() {
+        for (int i = 0; i < mCpuFreqPolicyDirs.length; i++) {
+            File policyDir = mCpuFreqPolicyDirs[i];
+            long maxCpuFreqKHz = readMaxCpuFrequency(policyDir);
+            if (maxCpuFreqKHz == 0) {
+                Slogf.w(TAG, "Invalid max CPU frequency read from %s", policyDir.getAbsolutePath());
+                continue;
+            }
+            File cpuCoresFile = new File(policyDir, RELATED_CPUS_FILE);
+            List<Integer> cpuCores = readCpuCores(cpuCoresFile);
+            if (cpuCores.isEmpty()) {
+                Slogf.e(TAG, "Failed to read CPU cores from %s", cpuCoresFile.getAbsolutePath());
+                continue;
+            }
+            for (int j = 0; j < cpuCores.size(); j++) {
+                mMaxCpuFrequenciesByCpus.append(cpuCores.get(j), maxCpuFreqKHz);
+            }
+        }
+    }
+
+    private long readMaxCpuFrequency(File policyDir) {
+        long curCpuFreqKHz = readCpuFreqKHz(new File(policyDir, MAX_CPUFREQ_FILE));
+        return curCpuFreqKHz > 0 ? curCpuFreqKHz
+                : readCpuFreqKHz(new File(policyDir, MAX_SCALING_FREQ_FILE));
+    }
+
+    private static long readCpuFreqKHz(File file) {
+        if (!file.exists()) {
+            Slogf.e(TAG, "CPU frequency file %s doesn't exist", file.getAbsolutePath());
+            return 0;
+        }
+        try {
+            List<String> lines = Files.readAllLines(file.toPath());
+            if (!lines.isEmpty()) {
+                long frequency = Long.parseLong(lines.get(0).trim());
+                return frequency > 0 ? frequency : 0;
+            }
+        } catch (Exception e) {
+            Slogf.e(TAG, e, "Failed to read integer content from file: %s", file.getAbsolutePath());
+        }
+        return 0;
+    }
+
+    /**
+     * Reads the list of CPU cores from the given file.
+     *
+     * Reads CPU cores represented in one of the below formats.
+     * <ul>
+     * <li> Single core id. Eg: 1
+     * <li> Core id range. Eg: 1-4
+     * <li> Comma separated values. Eg: 1, 3-5, 7
+     * </ul>
+     */
+    private static List<Integer> readCpuCores(File file) {
+        if (!file.exists()) {
+            Slogf.e(TAG, "Failed to read CPU cores as the file '%s' doesn't exist",
+                    file.getAbsolutePath());
+            return Collections.emptyList();
+        }
+        try {
+            List<String> lines = Files.readAllLines(file.toPath());
+            List<Integer> cpuCores = new ArrayList<>();
+            for (int i = 0; i < lines.size(); i++) {
+                String[] pairs = lines.get(i).trim().split(",");
+                for (int j = 0; j < pairs.length; j++) {
+                    String[] minMaxPairs = pairs[j].split("-");
+                    if (minMaxPairs.length >= 2) {
+                        int min = Integer.parseInt(minMaxPairs[0]);
+                        int max = Integer.parseInt(minMaxPairs[1]);
+                        if (min > max) {
+                            continue;
+                        }
+                        for (int id = min; id <= max; id++) {
+                            cpuCores.add(id);
+                        }
+                    } else if (minMaxPairs.length == 1) {
+                        cpuCores.add(Integer.parseInt(minMaxPairs[0]));
+                    } else {
+                        Slogf.w(TAG, "Invalid CPU core range format %s", pairs[j]);
+                    }
+                }
+            }
+            return cpuCores;
+        } catch (Exception e) {
+            Slogf.e(TAG, e, "Failed to read CPU cores from %s", file.getAbsolutePath());
+        }
+        return Collections.emptyList();
+    }
+}