Bug 1503776 - Save default value of WebRender rollout pref to user pref, check on startup. r=mattwoodrow
☠☠ backed out by 8ada4020596a ☠ ☠
authorChris Pearce <cpearce@mozilla.com>
Mon, 19 Nov 2018 19:18:06 +0000
changeset 503477 fb616c66a1fd330cdbdaa8494bbd38b4b18ff1f0
parent 503476 bd4cebdbed4bcd34d449f67d51f139f9bdf75edc
child 503478 bcb35a8cb22b1d55a357fa592cfbe2418c6ae9ae
push id10290
push userffxbld-merge
push dateMon, 03 Dec 2018 16:23:23 +0000
treeherdermozilla-beta@700bed2445e6 [default view] [failures only]
perfherder[talos] [build metrics] [platform microbench] (compared to previous push)
reviewersmattwoodrow
bugs1503776
milestone65.0a1
first release with
nightly linux32
nightly linux64
nightly mac
nightly win32
nightly win64
last release without
nightly linux32
nightly linux64
nightly mac
nightly win32
nightly win64
Bug 1503776 - Save default value of WebRender rollout pref to user pref, check on startup. r=mattwoodrow Normandy's Preference Rollout code sets default values on prefs, not user values (see uses of PrefUtils.setPref() in PreferenceRolloutAction.jsm). Default prefs are not persistent; unlike user prefs, changes to default pref values are not stored on disk. Changes to default values are only made on the in-memory copy of the pref's value, and thus don't survive a browser restart. Normandy changes the rolled out prefs early on in the startup of the browser, but not before gfxPlatform::Init() runs. So that means gfx can't use Normandy pref rollout to gradually rollout WebRender to release, as gfxPlatform::InitWebRenderConfig() won't see the rolled out version of the pref in time to turn on WebRender. So to work around this, add a profile-before-change shutdown observer that saves the default value of the gfx.webrender.all.qualified pref to a new user pref, gfx.webrender.all.qualified.default. We check that on startup and emulate the behavior that the pref system would have if that pref default value had already been set by Normandy. Differential Revision: https://phabricator.services.mozilla.com/D10527
gfx/thebes/gfxPlatform.cpp
gfx/thebes/gfxPrefs.h
--- a/gfx/thebes/gfxPlatform.cpp
+++ b/gfx/thebes/gfxPlatform.cpp
@@ -758,16 +758,94 @@ WebRenderMemoryReporter::CollectReports(
     [](mozilla::ipc::ResponseRejectReason aReason) {
       FinishAsyncMemoryReport();
     }
   );
 
   return NS_OK;
 }
 
+static const char* const WR_ROLLOUT_PREF = "gfx.webrender.all.qualified";
+static const char* const WR_ROLLOUT_PREF_DEFAULT =
+  "gfx.webrender.all.qualified.default";
+static const char* const WR_ROLLOUT_PREF_OVERRIDE =
+  "gfx.webrender.all.qualified.gfxPref-default-override";
+static const char* const WR_ROLLOUT_HW_QUALIFIED_OVERRIDE =
+  "gfx.webrender.all.qualified.hardware-override";
+static const char* const PROFILE_BEFORE_CHANGE_TOPIC = "profile-before-change";
+
+// If the "gfx.webrender.all.qualified" pref is true we want to enable
+// WebRender for qualified hardware. This pref may be set by the Normandy
+// Preference Rollout feature. The Normandy pref rollout code sets default
+// values on rolled out prefs on every startup. Default pref values are not
+// persisted; they only exist in memory for that session. Gfx starts up
+// before Normandy does. So it's too early to observe the WR qualified pref
+// changed by Normandy rollout on gfx startup. So we add a shutdown observer to
+// save the default value on shutdown, and read the saved value on startup
+// instead.
+class WrRolloutPrefShutdownSaver : public nsIObserver
+{
+public:
+  NS_DECL_ISUPPORTS
+
+  NS_IMETHOD Observe(nsISupports*, const char* aTopic, const char16_t*) override
+  {
+    if (strcmp(PROFILE_BEFORE_CHANGE_TOPIC, aTopic) != 0) {
+      // Not the observer we're looking for, move along.
+      return NS_OK;
+    }
+
+    SaveRolloutPref();
+
+    // Shouldn't receive another notification, remove the observer.
+    RefPtr<WrRolloutPrefShutdownSaver> kungFuDeathGrip(this);
+    nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+    if (NS_WARN_IF(!observerService)) {
+      return NS_ERROR_FAILURE;
+    }
+    observerService->RemoveObserver(this, PROFILE_BEFORE_CHANGE_TOPIC);
+    return NS_OK;
+  }
+
+  static void AddShutdownObserver()
+  {
+    MOZ_ASSERT(XRE_IsParentProcess());
+    nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+    if (NS_WARN_IF(!observerService)) {
+      return;
+    }
+    RefPtr<WrRolloutPrefShutdownSaver> wrRolloutSaver =
+      new WrRolloutPrefShutdownSaver();
+    observerService->AddObserver(
+      wrRolloutSaver, PROFILE_BEFORE_CHANGE_TOPIC, false);
+  }
+
+private:
+  virtual ~WrRolloutPrefShutdownSaver() = default;
+
+  void SaveRolloutPref()
+  {
+    if (Preferences::HasUserValue(WR_ROLLOUT_PREF) ||
+        Preferences::GetType(WR_ROLLOUT_PREF) == nsIPrefBranch::PREF_INVALID) {
+      // Don't need to create a backup of default value, because either:
+      // 1. the user or the WR SHIELD study has set a user pref value, or
+      // 2. we've not had a default pref set by Normandy that needs to be saved
+      //    for reading before Normandy has started up.
+      return;
+    }
+
+    bool defaultValue =
+      Preferences::GetBool(WR_ROLLOUT_PREF, false, PrefValueKind::Default);
+    Preferences::SetBool(WR_ROLLOUT_PREF_DEFAULT, defaultValue);
+  }
+};
+
+NS_IMPL_ISUPPORTS(WrRolloutPrefShutdownSaver, nsIObserver)
 
 void
 gfxPlatform::Init()
 {
     MOZ_RELEASE_ASSERT(!XRE_IsGPUProcess(), "GFX: Not allowed in GPU process.");
     MOZ_RELEASE_ASSERT(!XRE_IsRDDProcess(), "GFX: Not allowed in RDD process.");
     MOZ_RELEASE_ASSERT(NS_IsMainThread(), "GFX: Not in main thread.");
 
@@ -804,16 +882,20 @@ gfxPlatform::Init()
         gfxVars::SetGREDirectory(nsString());
       } else {
         nsAutoString path;
         file->GetPath(path);
         gfxVars::SetGREDirectory(nsString(path));
       }
     }
 
+    if (XRE_IsParentProcess()) {
+      WrRolloutPrefShutdownSaver::AddShutdownObserver();
+    }
+
     // Drop a note in the crash report if we end up forcing an option that could
     // destabilize things.  New items should be appended at the end (of an existing
     // or in a new section), so that we don't have to know the version to interpret
     // these cryptic strings.
     {
       nsAutoCString forcedPrefs;
       // D2D prefs
       forcedPrefs.AppendPrintf("FP(D%d%d",
@@ -2684,58 +2766,79 @@ gfxPlatform::WebRenderPrefEnabled()
 
 /*static*/ bool
 gfxPlatform::WebRenderEnvvarEnabled()
 {
   const char* env = PR_GetEnv("MOZ_WEBRENDER");
   return (env && *env == '1');
 }
 
-void
-gfxPlatform::InitWebRenderConfig()
+// If the "gfx.webrender.all.qualified" pref is true we want to enable
+// WebRender for qualifying hardware. The Normandy pref rollout code sets
+// default values on rolled out prefs on every startup, but Gfx starts up
+// before Normandy does. So it's too early to observe the WR qualified pref
+// default value changed by Normandy rollout here yet. So we have a shutdown
+// observer to save the default value on shutdown, and read the saved default
+// value here instead, and emulate the behavior of the pref system, with
+// respect to default/user values of the rollout pref.
+static bool
+CalculateWrQualifiedPrefValue()
 {
-  bool prefEnabled = WebRenderPrefEnabled();
-  bool envvarEnabled = WebRenderEnvvarEnabled();
-
-  // On Nightly:
-  //   WR? WR+   => means WR was enabled via gfx.webrender.all.qualified
-  //   WR! WR+   => means WR was enabled via gfx.webrender.{all,enabled} or envvar
-  // On Beta/Release:
-  //   WR? WR+   => means WR was enabled via gfx.webrender.all.qualified on qualified hardware
-  //   WR! WR+   => means WR was enabled via envvar, possibly on unqualified hardware.
-  // In all cases WR- means WR was not enabled, for one of many possible reasons.
-  ScopedGfxFeatureReporter reporter("WR", prefEnabled || envvarEnabled);
-  if (!XRE_IsParentProcess()) {
-    // Force-disable WebRender in recording/replaying child processes, which
-    // have their own compositor.
-    if (recordreplay::IsRecordingOrReplaying()) {
-      gfxVars::SetUseWebRender(false);
-    }
-
-    // The parent process runs through all the real decision-making code
-    // later in this function. For other processes we still want to report
-    // the state of the feature for crash reports.
-    if (gfxVars::UseWebRender()) {
-      reporter.SetSuccessful();
-    }
-    return;
+  auto clearPrefOnExit = MakeScopeExit([]() {
+    // Clear the mirror of the default value of the rollout pref on scope exit,
+    // if we have one. This ensures the user doesn't mess with the pref.
+    // If we need it again, we'll re-create it on shutdown.
+    Preferences::ClearUser(WR_ROLLOUT_PREF_DEFAULT);
+  });
+
+  if (!Preferences::HasUserValue(WR_ROLLOUT_PREF) &&
+      Preferences::HasUserValue(WR_ROLLOUT_PREF_DEFAULT)) {
+    // The user has not set a user pref, and we have a default value set by the
+    // shutdown observer. We should use that instead of the gfxPref's default,
+    // as if Normandy had a chance to set it before startup, that is the value
+    // gfxPrefs would return, rather than the default set by DECL_GFX_PREF.
+    return gfxPrefs::WebRenderAllQualifiedDefault();
   }
 
+  // We don't have a user value for the rollout pref, and we don't have the
+  // value of the rollout pref at last shutdown stored. So we should fallback
+  // to using whatever default is stored in the gfxPref. *But* if we're running
+  // under the Marionette pref rollout work-around test, we may want to override
+  // the default value expressed here, so we can test the "default disabled;
+  // rollout pref enabled" case.
+  if (Preferences::HasUserValue(WR_ROLLOUT_PREF_OVERRIDE)) {
+    return Preferences::GetBool(WR_ROLLOUT_PREF_OVERRIDE);
+  }
+  return gfxPrefs::WebRenderAllQualified();
+}
+
+static FeatureState&
+WebRenderHardwareQualificationStatus(bool aHasBattery, nsCString& aOutFailureId)
+{
   FeatureState& featureWebRenderQualified = gfxConfig::GetFeature(Feature::WEBRENDER_QUALIFIED);
   featureWebRenderQualified.EnableByDefault();
+
+  if (Preferences::HasUserValue(WR_ROLLOUT_HW_QUALIFIED_OVERRIDE)) {
+    if (!Preferences::GetBool(WR_ROLLOUT_HW_QUALIFIED_OVERRIDE)) {
+      featureWebRenderQualified.Disable(
+        FeatureStatus::Blocked,
+        "HW qualification pref override",
+        NS_LITERAL_CSTRING("FEATURE_FAILURE_WR_QUALIFICATION_OVERRIDE"));
+    }
+    return featureWebRenderQualified;
+  }
+
   nsCOMPtr<nsIGfxInfo> gfxInfo = services::GetGfxInfo();
-  nsCString failureId;
   int32_t status;
-  if (NS_SUCCEEDED(gfxInfo->GetFeatureStatus(nsIGfxInfo::FEATURE_WEBRENDER,
-                                             failureId, &status))) {
+  if (NS_SUCCEEDED(gfxInfo->GetFeatureStatus(
+        nsIGfxInfo::FEATURE_WEBRENDER, aOutFailureId, &status))) {
     if (status != nsIGfxInfo::FEATURE_STATUS_OK) {
-      featureWebRenderQualified.Disable(FeatureStatus::Blocked,
-                                         "No qualified hardware",
-                                         failureId);
-    } else if (HasBattery()) {
+      featureWebRenderQualified.Disable(
+        FeatureStatus::Blocked, "No qualified hardware", aOutFailureId);
+    } else if (aHasBattery) {
       featureWebRenderQualified.Disable(FeatureStatus::Blocked,
                                          "Has battery",
                                          NS_LITERAL_CSTRING("FEATURE_FAILURE_WR_HAS_BATTERY"));
     } else {
       nsAutoString adapterVendorID;
       gfxInfo->GetAdapterVendorID(adapterVendorID);
       if (adapterVendorID != u"0x10de") {
         featureWebRenderQualified.Disable(FeatureStatus::Blocked,
@@ -2759,38 +2862,75 @@ gfxPlatform::InitWebRenderConfig()
         }
       }
     }
   } else {
     featureWebRenderQualified.Disable(FeatureStatus::Blocked,
                                        "gfxInfo is broken",
                                        NS_LITERAL_CSTRING("FEATURE_FAILURE_WR_NO_GFX_INFO"));
   }
-
+  return featureWebRenderQualified;
+}
+
+void
+gfxPlatform::InitWebRenderConfig()
+{
+  bool prefEnabled = WebRenderPrefEnabled();
+  bool envvarEnabled = WebRenderEnvvarEnabled();
+
+  // On Nightly:
+  //   WR? WR+   => means WR was enabled via gfx.webrender.all.qualified
+  //   WR! WR+   => means WR was enabled via gfx.webrender.{all,enabled} or envvar
+  // On Beta/Release:
+  //   WR? WR+   => means WR was enabled via gfx.webrender.all.qualified on qualified hardware
+  //   WR! WR+   => means WR was enabled via envvar, possibly on unqualified hardware.
+  // In all cases WR- means WR was not enabled, for one of many possible reasons.
+  ScopedGfxFeatureReporter reporter("WR", prefEnabled || envvarEnabled);
+  if (!XRE_IsParentProcess()) {
+    // Force-disable WebRender in recording/replaying child processes, which
+    // have their own compositor.
+    if (recordreplay::IsRecordingOrReplaying()) {
+      gfxVars::SetUseWebRender(false);
+    }
+
+    // The parent process runs through all the real decision-making code
+    // later in this function. For other processes we still want to report
+    // the state of the feature for crash reports.
+    if (gfxVars::UseWebRender()) {
+      reporter.SetSuccessful();
+    }
+    return;
+  }
+
+  nsCString failureId;
+  FeatureState& featureWebRenderQualified =
+    WebRenderHardwareQualificationStatus(HasBattery(), failureId);
   FeatureState& featureWebRender = gfxConfig::GetFeature(Feature::WEBRENDER);
 
   featureWebRender.DisableByDefault(
       FeatureStatus::OptIn,
       "WebRender is an opt-in feature",
       NS_LITERAL_CSTRING("FEATURE_FAILURE_DEFAULT_OFF"));
 
+  const bool wrQualifiedAll = CalculateWrQualifiedPrefValue();
+
   // envvar works everywhere; we need this for testing in CI. Sadly this allows
   // beta/release to enable it on unqualified hardware, but at least this is
   // harder for the average person than flipping a pref.
   if (envvarEnabled) {
     featureWebRender.UserEnable("Force enabled by envvar");
 
   // gfx.webrender.enabled and gfx.webrender.all only work on nightly
 #ifdef NIGHTLY_BUILD
   } else if (prefEnabled) {
     featureWebRender.UserEnable("Force enabled by pref");
 #endif
 
   // gfx.webrender.all.qualified works on all channels
-  } else if (gfxPrefs::WebRenderAllQualified()) {
+  } else if (wrQualifiedAll) {
     if (featureWebRenderQualified.IsEnabled()) {
       featureWebRender.UserEnable("Qualified enabled by pref ");
     } else {
       featureWebRender.ForceDisable(FeatureStatus::Blocked,
                                     "Qualified enable blocked",
                                     failureId);
     }
   }
--- a/gfx/thebes/gfxPrefs.h
+++ b/gfx/thebes/gfxPrefs.h
@@ -527,16 +527,21 @@ private:
   DECL_GFX_PREF(Once, "gfx.use-mutex-on-present",              UseMutexOnPresent, bool, false);
   DECL_GFX_PREF(Once, "gfx.use-surfacetexture-textures",       UseSurfaceTextureTextures, bool, false);
   DECL_GFX_PREF(Once, "gfx.allow-texture-direct-mapping",      AllowTextureDirectMapping, bool, true);
   DECL_GFX_PREF(Live, "gfx.vsync.collect-scroll-transforms",   CollectScrollTransforms, bool, false);
   DECL_GFX_PREF(Once, "gfx.vsync.compositor.unobserve-count",  CompositorUnobserveCount, int32_t, 10);
 
   DECL_GFX_PREF(Once, "gfx.webrender.all",                     WebRenderAll, bool, false);
   DECL_GFX_PREF(Once, "gfx.webrender.all.qualified",           WebRenderAllQualified, bool, true);
+  DECL_GFX_PREF(Once,
+                "gfx.webrender.all.qualified.default",
+                WebRenderAllQualifiedDefault,
+                bool,
+                false);
   DECL_GFX_PREF(Live, "gfx.webrender.blob-images",             WebRenderBlobImages, bool, true);
   DECL_GFX_PREF(Live, "gfx.webrender.blob.invalidation",       WebRenderBlobInvalidation, bool, false);
   DECL_GFX_PREF(Live, "gfx.webrender.blob.paint-flashing",     WebRenderBlobPaintFlashing, bool, false);
   DECL_GFX_PREF(Live, "gfx.webrender.dl.dump-parent",          WebRenderDLDumpParent, bool, false);
   DECL_GFX_PREF(Live, "gfx.webrender.dl.dump-content",         WebRenderDLDumpContent, bool, false);
   DECL_GFX_PREF(Once, "gfx.webrender.enabled",                 WebRenderEnabledDoNotUseDirectly, bool, false);
   DECL_GFX_PREF(Once, "gfx.webrender.force-disabled",          WebRenderForceDisabled, bool, false);
   DECL_GFX_PREF(Live, "gfx.webrender.highlight-painted-layers",WebRenderHighlightPaintedLayers, bool, false);