Create a Zram writeback job
Zram on some devices can support writing idle pages
on to disk. ZramWriteback schedules jobs to track idle
pages and trigger write-to-disk when the device is idle.
Note: This is the same change that was reviewed in aosp. I am doing
a manual merge to avoid automerger merge conflicts.
Bug: 117682284
Bug: 122674343
Test: dumpsys jobscheduler
No jobs should be scheduled for devices with no support for
zram writeback or if they do not have low_ram flag set.
Change-Id: Id1bc41ac32f2c63e241270c10a07560bda39a127
diff --git a/services/core/java/com/android/server/ZramWriteback.java b/services/core/java/com/android/server/ZramWriteback.java
new file mode 100644
index 0000000..3a4aff2
--- /dev/null
+++ b/services/core/java/com/android/server/ZramWriteback.java
@@ -0,0 +1,187 @@
+/*
+ * 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.
+ */
+
+package com.android.server;
+
+import android.app.job.JobInfo;
+import android.app.job.JobParameters;
+import android.app.job.JobScheduler;
+import android.app.job.JobService;
+import android.content.ComponentName;
+import android.content.Context;
+import android.os.FileUtils;
+import android.os.SystemProperties;
+import android.util.Slog;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Schedules jobs for triggering zram writeback.
+ */
+public final class ZramWriteback extends JobService {
+ private static final String TAG = "ZramWriteback";
+ private static final boolean DEBUG = false;
+
+ private static final ComponentName sZramWriteback =
+ new ComponentName("android", ZramWriteback.class.getName());
+
+ private static final int MARK_IDLE_JOB_ID = 811;
+ private static final int WRITEBACK_IDLE_JOB_ID = 812;
+
+ private static final int MAX_ZRAM_DEVICES = 256;
+ private static int sZramDeviceId = 0;
+
+ private static final String IDLE_SYS = "/sys/block/zram%d/idle";
+ private static final String IDLE_SYS_ALL_PAGES = "all";
+
+ private static final String WB_SYS = "/sys/block/zram%d/writeback";
+ private static final String WB_SYS_IDLE_PAGES = "idle";
+
+ private static final String WB_STATS_SYS = "/sys/block/zram%d/bd_stat";
+ private static final int WB_STATS_MAX_FILE_SIZE = 128;
+
+ private static final String BDEV_SYS = "/sys/block/zram%d/backing_dev";
+
+ private static final String MARK_IDLE_DELAY_PROP = "ro.zram.mark_idle_delay_mins";
+ private static final String FIRST_WB_DELAY_PROP = "ro.zram.first_wb_delay_mins";
+ private static final String PERIODIC_WB_DELAY_PROP = "ro.zram.periodic_wb_delay_hours";
+
+ private void markPagesAsIdle() {
+ String idlePath = String.format(IDLE_SYS, sZramDeviceId);
+ try {
+ FileUtils.stringToFile(new File(idlePath), IDLE_SYS_ALL_PAGES);
+ } catch (IOException e) {
+ Slog.e(TAG, "Failed to write to " + idlePath);
+ }
+ }
+
+ private void flushIdlePages() {
+ if (DEBUG) Slog.d(TAG, "Start writing back idle pages to disk");
+ String wbPath = String.format(WB_SYS, sZramDeviceId);
+ try {
+ FileUtils.stringToFile(new File(wbPath), WB_SYS_IDLE_PAGES);
+ } catch (IOException e) {
+ Slog.e(TAG, "Failed to write to " + wbPath);
+ }
+ if (DEBUG) Slog.d(TAG, "Finished writeback back idle pages");
+ }
+
+ private int getWrittenPageCount() {
+ String wbStatsPath = String.format(WB_STATS_SYS, sZramDeviceId);
+ try {
+ String wbStats = FileUtils
+ .readTextFile(new File(wbStatsPath), WB_STATS_MAX_FILE_SIZE, "");
+ return Integer.parseInt(wbStats.trim().split("\\s+")[2], 10);
+ } catch (IOException e) {
+ Slog.e(TAG, "Failed to read writeback stats from " + wbStatsPath);
+ }
+
+ return -1;
+ }
+
+ private void markAndFlushPages() {
+ int pageCount = getWrittenPageCount();
+
+ flushIdlePages();
+ markPagesAsIdle();
+
+ if (pageCount != -1) {
+ Slog.i(TAG, "Total pages written to disk is " + (getWrittenPageCount() - pageCount));
+ }
+ }
+
+ private static boolean isWritebackEnabled() {
+ try {
+ String backingDev = FileUtils
+ .readTextFile(new File(String.format(BDEV_SYS, sZramDeviceId)), 128, "");
+ if (!"none".equals(backingDev.trim())) {
+ return true;
+ } else {
+ Slog.w(TAG, "Writeback device is not set");
+ }
+ } catch (IOException e) {
+ Slog.w(TAG, "Writeback is not enabled on zram");
+ }
+ return false;
+ }
+
+ private static void schedNextWriteback(Context context) {
+ int nextWbDelay = SystemProperties.getInt(PERIODIC_WB_DELAY_PROP, 24);
+ JobScheduler js = (JobScheduler) context.getSystemService(Context.JOB_SCHEDULER_SERVICE);
+
+ js.schedule(new JobInfo.Builder(WRITEBACK_IDLE_JOB_ID, sZramWriteback)
+ .setMinimumLatency(TimeUnit.HOURS.toMillis(nextWbDelay))
+ .setRequiresDeviceIdle(true)
+ .build());
+ }
+
+ @Override
+ public boolean onStartJob(JobParameters params) {
+
+ if (!isWritebackEnabled()) {
+ jobFinished(params, false);
+ return false;
+ }
+
+ if (params.getJobId() == MARK_IDLE_JOB_ID) {
+ markPagesAsIdle();
+ jobFinished(params, false);
+ return false;
+ } else {
+ new Thread("ZramWriteback_WritebackIdlePages") {
+ @Override
+ public void run() {
+ markAndFlushPages();
+ schedNextWriteback(ZramWriteback.this);
+ jobFinished(params, false);
+ }
+ }.start();
+ }
+ return true;
+ }
+
+ @Override
+ public boolean onStopJob(JobParameters params) {
+ // The thread that triggers the writeback is non-interruptible
+ return false;
+ }
+
+ /**
+ * Schedule the zram writeback job to trigger a writeback when idle
+ */
+ public static void scheduleZramWriteback(Context context) {
+ int markIdleDelay = SystemProperties.getInt(MARK_IDLE_DELAY_PROP, 20);
+ int firstWbDelay = SystemProperties.getInt(FIRST_WB_DELAY_PROP, 180);
+
+ JobScheduler js = (JobScheduler) context.getSystemService(Context.JOB_SCHEDULER_SERVICE);
+
+ // Schedule a one time job to mark pages as idle. These pages will be written
+ // back at later point if they remain untouched.
+ js.schedule(new JobInfo.Builder(MARK_IDLE_JOB_ID, sZramWriteback)
+ .setMinimumLatency(TimeUnit.MINUTES.toMillis(markIdleDelay))
+ .build());
+
+ // Schedule a one time job to flush idle pages to disk.
+ // After the initial writeback, subsequent writebacks are done at interval set
+ // by ro.zram.periodic_wb_delay_hours.
+ js.schedule(new JobInfo.Builder(WRITEBACK_IDLE_JOB_ID, sZramWriteback)
+ .setMinimumLatency(TimeUnit.MINUTES.toMillis(firstWbDelay))
+ .setRequiresDeviceIdle(true)
+ .build());
+ }
+}