Add experiment param to configure reached code sampling interval

BUG=916263

Change-Id: I2bb13e274d18e1dac5d0a91ac86cbd0cdbf2cc18
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2263473
Commit-Queue: ssid <ssid@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Reviewed-by: Egor Pasko <pasko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782760}

base/android/java/src/org/chromium/base/BaseSwitches.java

@@ -30,6 +30,10 @@ public abstract class BaseSwitches {
     // Enables the reached code profiler.
     public static final String ENABLE_REACHED_CODE_PROFILER = "enable-reached-code-profiler";
 
+    // Specifies the profiling interval for reached code profiler in microseconds.
+    public static final String REACHED_CODE_SAMPLING_INTERVAL_US =
+            "reached-code-sampling-interval-us";
+
     // Comma-separated list of feature names to enable.
     public static final String ENABLE_FEATURES = "enable-features";
 

base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java

@@ -6,6 +6,7 @@ package org.chromium.base.library_loader;
 
 import android.annotation.SuppressLint;
 import android.content.Context;
+import android.content.SharedPreferences;
 import android.content.pm.ApplicationInfo;
 import android.os.Build;
 import android.os.Build.VERSION_CODES;
@@ -63,7 +64,13 @@ public class LibraryLoader {
     private static final String LIBRARY_DIR = "native_libraries";
 
     // Shared preferences key for the reached code profiler.
-    private static final String REACHED_CODE_PROFILER_ENABLED_KEY = "reached_code_profiler_enabled";
+    private static final String DEPRECATED_REACHED_CODE_PROFILER_KEY =
+            "reached_code_profiler_enabled";
+    private static final String REACHED_CODE_SAMPLING_INTERVAL_KEY =
+            "reached_code_sampling_interval";
+
+    // Default sampling interval for reached code profiler in microseconds.
+    private static final int DEFAULT_REACHED_CODE_SAMPLING_INTERVAL_US = 10000;
 
     // The singleton instance of LibraryLoader. Never null (not final for tests).
     private static LibraryLoader sInstance = new LibraryLoader();
@@ -376,23 +383,35 @@ public class LibraryLoader {
      * on ChromeFeatureList, and has to rely on external code pushing the value.
      *
      * @param enabled whether to enable the reached code profiler.
+     * @param samplingIntervalUs the sampling interval for reached code profiler.
      */
-    public static void setReachedCodeProfilerEnabledOnNextRuns(boolean enabled) {
-        ContextUtils.getAppSharedPreferences()
-                .edit()
-                .putBoolean(REACHED_CODE_PROFILER_ENABLED_KEY, enabled)
-                .apply();
+    public static void setReachedCodeProfilerEnabledOnNextRuns(
+            boolean enabled, int samplingIntervalUs) {
+        // Store 0 if the profiler is not enabled, otherwise store the sampling interval in
+        // microseconds.
+        if (enabled && samplingIntervalUs == 0) {
+            samplingIntervalUs = DEFAULT_REACHED_CODE_SAMPLING_INTERVAL_US;
+        } else if (!enabled) {
+            samplingIntervalUs = 0;
+        }
+        SharedPreferences.Editor editor = ContextUtils.getAppSharedPreferences().edit();
+        editor.remove(DEPRECATED_REACHED_CODE_PROFILER_KEY);
+        editor.putInt(REACHED_CODE_SAMPLING_INTERVAL_KEY, samplingIntervalUs).apply();
     }
 
     /**
-     * @return whether to enable reached code profiler (see
+     * @return sampling interval for reached code profiler, or 0 when the profiler is disabled. (see
      *         setReachedCodeProfilerEnabledOnNextRuns()).
      */
     @VisibleForTesting
-    public static boolean isReachedCodeProfilerEnabled() {
+    public static int getReachedCodeSamplingIntervalUs() {
         try (StrictModeContext ignored = StrictModeContext.allowDiskReads()) {
-            return ContextUtils.getAppSharedPreferences().getBoolean(
-                    REACHED_CODE_PROFILER_ENABLED_KEY, false);
+            if (ContextUtils.getAppSharedPreferences().getBoolean(
+                        DEPRECATED_REACHED_CODE_PROFILER_KEY, false)) {
+                return DEFAULT_REACHED_CODE_SAMPLING_INTERVAL_US;
+            }
+            return ContextUtils.getAppSharedPreferences().getInt(
+                    REACHED_CODE_SAMPLING_INTERVAL_KEY, 0);
         }
     }
 
@@ -581,9 +600,14 @@ public class LibraryLoader {
 
         // Add a switch for the reached code profiler as late as possible since it requires a read
         // from the shared preferences. At this point the shared preferences are usually warmed up.
-        if (mLibraryProcessType == LibraryProcessType.PROCESS_BROWSER
-                && isReachedCodeProfilerEnabled()) {
-            CommandLine.getInstance().appendSwitch(BaseSwitches.ENABLE_REACHED_CODE_PROFILER);
+        if (mLibraryProcessType == LibraryProcessType.PROCESS_BROWSER) {
+            int reachedCodeSamplingIntervalUs = getReachedCodeSamplingIntervalUs();
+            if (reachedCodeSamplingIntervalUs > 0) {
+                CommandLine.getInstance().appendSwitch(BaseSwitches.ENABLE_REACHED_CODE_PROFILER);
+                CommandLine.getInstance().appendSwitchWithValue(
+                        BaseSwitches.REACHED_CODE_SAMPLING_INTERVAL_US,
+                        Integer.toString(reachedCodeSamplingIntervalUs));
+            }
         }
 
         ensureCommandLineSwitchedAlreadyLocked();

base/android/reached_code_profiler.cc

@@ -28,6 +28,7 @@
 #include "base/path_service.h"
 #include "base/scoped_generic.h"
 #include "base/single_thread_task_runner.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/lock.h"
@@ -117,7 +118,8 @@ class ReachedCodeProfiler {
   }
 
   // Starts to periodically send |kProfilerSignal| to all threads.
-  void Start(LibraryProcessType library_process_type) {
+  void Start(LibraryProcessType library_process_type,
+             base::TimeDelta sampling_interval) {
     if (is_enabled_)
       return;
 
@@ -154,7 +156,7 @@ class ReachedCodeProfiler {
     // Start the interval timer.
     struct itimerspec its;
     memset(&its, 0, sizeof(its));
-    its.it_interval.tv_nsec = kSamplingInterval.InNanoseconds();
+    its.it_interval.tv_nsec = sampling_interval.InNanoseconds();
     its.it_value = its.it_interval;
     ret = timer_settime(timerid, 0, &its, nullptr);
     if (ret) {
@@ -268,7 +270,17 @@ void InitReachedCodeProfilerAtStartup(LibraryProcessType library_process_type) {
   if (!ShouldEnableReachedCodeProfiler())
     return;
 
-  ReachedCodeProfiler::GetInstance()->Start(library_process_type);
+  int interval_us = 0;
+  base::TimeDelta sampling_interval = kSamplingInterval;
+  if (base::StringToInt(
+          base::CommandLine::ForCurrentProcess()->GetSwitchValueNative(
+              switches::kReachedCodeSamplingIntervalUs),
+          &interval_us) &&
+      interval_us > 0) {
+    sampling_interval = base::TimeDelta::FromMicroseconds(interval_us);
+  }
+  ReachedCodeProfiler::GetInstance()->Start(library_process_type,
+                                            sampling_interval);
 }
 
 bool IsReachedCodeProfilerEnabled() {

base/base_switches.cc

@@ -136,6 +136,10 @@ const char kEnableCrashReporterForTesting[] =
 // Enables the reached code profiler that samples all threads in all processes
 // to determine which functions are almost never executed.
 const char kEnableReachedCodeProfiler[] = "enable-reached-code-profiler";
+
+// Specifies the profiling interval in microseconds for reached code profiler.
+const char kReachedCodeSamplingIntervalUs[] =
+    "reached-code-sampling-interval-us";
 #endif
 
 #if defined(OS_LINUX)

base/base_switches.h

@@ -48,6 +48,7 @@ extern const char kEnableCrashReporterForTesting[];
 
 #if defined(OS_ANDROID)
 extern const char kEnableReachedCodeProfiler[];
+extern const char kReachedCodeSamplingIntervalUs[];
 extern const char kOrderfileMemoryOptimization[];
 #endif
 

chrome/android/javatests/src/org/chromium/chrome/browser/ReachedCodeProfilerTest.java

@@ -54,11 +54,17 @@ public final class ReachedCodeProfilerTest {
      */
     @Test
     @SmallTest
-    @EnableFeatures(ChromeFeatureList.REACHED_CODE_PROFILER)
-    public void testEnabledViaCachedSharedPreference() {
-        LibraryLoader.setReachedCodeProfilerEnabledOnNextRuns(true);
+    @CommandLineFlags.Add({"enable-features=" + ChromeFeatureList.REACHED_CODE_PROFILER + "<"
+                    + ChromeFeatureList.REACHED_CODE_PROFILER,
+            "force-fieldtrials=" + ChromeFeatureList.REACHED_CODE_PROFILER + "/" + FAKE_GROUP_NAME,
+            "force-fieldtrial-params=" + ChromeFeatureList.REACHED_CODE_PROFILER + "."
+                    + FAKE_GROUP_NAME + ":sampling_interval_us/42"})
+    public void
+    testEnabledViaCachedSharedPreference() {
+        LibraryLoader.setReachedCodeProfilerEnabledOnNextRuns(true, 42);
         mActivityTestRule.startMainActivityFromLauncher();
         assertReachedCodeProfilerIsEnabled();
+        Assert.assertEquals(42, LibraryLoader.getReachedCodeSamplingIntervalUs());
     }
 
     /**
@@ -71,7 +77,7 @@ public final class ReachedCodeProfilerTest {
     public void testSharedPreferenceIsCached_Enable() {
         mActivityTestRule.startMainActivityFromLauncher();
 
-        Assert.assertTrue(LibraryLoader.isReachedCodeProfilerEnabled());
+        Assert.assertEquals(10000, LibraryLoader.getReachedCodeSamplingIntervalUs());
         // Enabling takes effect only on the second startup.
         Assert.assertFalse(ReachedCodeProfiler.isEnabled());
     }
@@ -85,10 +91,9 @@ public final class ReachedCodeProfilerTest {
     @SmallTest
     @DisableFeatures(ChromeFeatureList.REACHED_CODE_PROFILER)
     public void testSharedPreferenceIsCached_Disable() {
-        LibraryLoader.setReachedCodeProfilerEnabledOnNextRuns(true);
+        LibraryLoader.setReachedCodeProfilerEnabledOnNextRuns(true, 0);
         mActivityTestRule.startMainActivityFromLauncher();
-
-        Assert.assertFalse(LibraryLoader.isReachedCodeProfilerEnabled());
+        Assert.assertEquals(0, LibraryLoader.getReachedCodeSamplingIntervalUs());
         // Disabling takes effect only on the second startup.
         assertReachedCodeProfilerIsEnabled();
     }

chrome/browser/flags/android/java/src/org/chromium/chrome/browser/flags/CachedFeatureFlags.java

@@ -248,7 +248,9 @@ public class CachedFeatureFlags {
         // Propagate REACHED_CODE_PROFILER feature value to LibraryLoader. This can't be done in
         // LibraryLoader itself because it lives in //base and can't depend on ChromeFeatureList.
         LibraryLoader.setReachedCodeProfilerEnabledOnNextRuns(
-                ChromeFeatureList.isEnabled(ChromeFeatureList.REACHED_CODE_PROFILER));
+                ChromeFeatureList.isEnabled(ChromeFeatureList.REACHED_CODE_PROFILER),
+                ChromeFeatureList.getFieldTrialParamByFeatureAsInt(
+                        ChromeFeatureList.REACHED_CODE_PROFILER, "sampling_interval_us", 0));
     }
 
     /**

content/browser/gpu/gpu_process_host.cc

@@ -282,6 +282,7 @@ static const char* const kSwitchNames[] = {
     switches::kForceVideoOverlays,
 #if defined(OS_ANDROID)
     switches::kEnableReachedCodeProfiler,
+    switches::kReachedCodeSamplingIntervalUs,
 #endif
 };
 

content/browser/renderer_host/render_process_host_impl.cc

@@ -3443,6 +3443,7 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
 #if defined(OS_ANDROID)
     switches::kDisableMediaSessionAPI,
     switches::kEnableReachedCodeProfiler,
+    switches::kReachedCodeSamplingIntervalUs,
     switches::kRendererWaitForJavaDebugger,
 #endif
 #if defined(OS_WIN)

content/browser/utility_process_host.cc

@@ -476,6 +476,7 @@ bool UtilityProcessHost::StartProcess() {
       switches::kVModule,
 #if defined(OS_ANDROID)
       switches::kEnableReachedCodeProfiler,
+      switches::kReachedCodeSamplingIntervalUs,
 #endif
       switches::kEnableExperimentalWebPlatformFeatures,
       // These flags are used by the audio service: