Add a sampling profiler and a script to generate profiles for use with Gecko tooling.

components/background_hang_monitor/Cargo.toml

@@ -21,6 +21,7 @@ libc = "0.2"
 log = "0.4"
 msg = {path = "../msg"}
 serde = "1.0.60"
+serde_json = "1.0"
 crossbeam-channel = "0.3"
 
 [target.'cfg(target_os = "macos")'.dependencies]

components/background_hang_monitor/background_hang_monitor.rs

@@ -2,16 +2,17 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use crate::sampler::Sampler;
+use crate::sampler::{NativeStack, Sampler};
 use crossbeam_channel::{after, unbounded, Receiver, Sender};
 use ipc_channel::ipc::IpcSender;
 use msg::constellation_msg::MonitoredComponentId;
 use msg::constellation_msg::{
     BackgroundHangMonitor, BackgroundHangMonitorClone, BackgroundHangMonitorRegister,
 };
-use msg::constellation_msg::{HangAlert, HangAnnotation};
+use msg::constellation_msg::{HangAlert, HangAnnotation, HangMonitorAlert};
 use std::cell::Cell;
 use std::collections::HashMap;
+use std::sync::Mutex;
 use std::thread;
 use std::time::{Duration, Instant};
 
@@ -20,18 +21,46 @@ pub struct HangMonitorRegister {
     sender: Sender<(MonitoredComponentId, MonitoredComponentMsg)>,
 }
 
+#[derive(Copy, Clone, PartialEq)]
+enum SamplerState {
+    NotSampling,
+    StartSampling(Duration),
+    Sampling,
+    Resolving,
+}
+
+lazy_static! {
+    static ref SAMPLING_STATE: Mutex<SamplerState> = Mutex::new(SamplerState::NotSampling);
+}
 impl HangMonitorRegister {
     /// Start a new hang monitor worker, and return a handle to register components for monitoring.
-    pub fn init(constellation_chan: IpcSender<HangAlert>) -> Box<BackgroundHangMonitorRegister> {
+    pub fn init(
+        constellation_chan: IpcSender<HangMonitorAlert>,
+    ) -> Box<BackgroundHangMonitorRegister> {
         let (sender, port) = unbounded();
         let _ = thread::Builder::new().spawn(move || {
-            let mut monitor = { BackgroundHangMonitorWorker::new(constellation_chan, port) };
+            let mut monitor = BackgroundHangMonitorWorker::new(constellation_chan, port);
             while monitor.run() {
                 // Monitoring until all senders have been dropped...
             }
         });
         Box::new(HangMonitorRegister { sender })
     }
+
+    pub fn toggle(rate: Duration) {
+        let state = *SAMPLING_STATE.lock().unwrap();
+        match state {
+            SamplerState::NotSampling => {
+                println!("Starting profiler.");
+                *SAMPLING_STATE.lock().unwrap() = SamplerState::StartSampling(rate);
+            },
+            SamplerState::Sampling => {
+                println!("Stopping profiler.");
+                *SAMPLING_STATE.lock().unwrap() = SamplerState::Resolving;
+            },
+            _ => (),
+        }
+    }
 }
 
 impl BackgroundHangMonitorRegister for HangMonitorRegister {
@@ -55,6 +84,7 @@ impl BackgroundHangMonitorRegister for HangMonitorRegister {
 
         bhm_chan.send(MonitoredComponentMsg::Register(
             sampler,
+            thread::current().name().map(str::to_owned),
             transient_hang_timeout,
             permanent_hang_timeout,
         ));
@@ -71,7 +101,7 @@ impl BackgroundHangMonitorClone for HangMonitorRegister {
 /// Messages sent from monitored components to the monitor.
 pub enum MonitoredComponentMsg {
     /// Register component for monitoring,
-    Register(Box<Sampler>, Duration, Duration),
+    Register(Box<Sampler>, Option<String>, Duration, Duration),
     /// Unregister component for monitoring.
     Unregister,
     /// Notify start of new activity for a given component,
@@ -138,25 +168,103 @@ struct MonitoredComponent {
     is_waiting: bool,
 }
 
+struct Sample(MonitoredComponentId, Instant, NativeStack);
+
 pub struct BackgroundHangMonitorWorker {
+    component_names: HashMap<MonitoredComponentId, String>,
     monitored_components: HashMap<MonitoredComponentId, MonitoredComponent>,
-    constellation_chan: IpcSender<HangAlert>,
+    constellation_chan: IpcSender<HangMonitorAlert>,
     port: Receiver<(MonitoredComponentId, MonitoredComponentMsg)>,
+    sampling_duration: Option<Duration>,
+    last_sample: Instant,
+    creation: Instant,
+    sampling_baseline: Instant,
+    samples: Vec<Sample>,
 }
 
 impl BackgroundHangMonitorWorker {
     pub fn new(
-        constellation_chan: IpcSender<HangAlert>,
+        constellation_chan: IpcSender<HangMonitorAlert>,
         port: Receiver<(MonitoredComponentId, MonitoredComponentMsg)>,
     ) -> Self {
         Self {
+            component_names: Default::default(),
             monitored_components: Default::default(),
             constellation_chan,
             port,
+            sampling_duration: None,
+            last_sample: Instant::now(),
+            sampling_baseline: Instant::now(),
+            creation: Instant::now(),
+            samples: vec![],
+        }
+    }
+
+    fn handle_sampling(&mut self) {
+        let state = *SAMPLING_STATE.lock().unwrap();
+        match state {
+            SamplerState::StartSampling(rate) => {
+                *SAMPLING_STATE.lock().unwrap() = SamplerState::Sampling;
+                self.sampling_duration = Some(rate);
+                self.sampling_baseline = Instant::now();
+            },
+            SamplerState::Resolving => {
+                let mut bytes = vec![];
+                bytes.extend(
+                    format!(
+                        "{{ \"rate\": {}, \"start\": {}, \"data\": [\n",
+                        self.sampling_duration.unwrap().as_millis(),
+                        (self.sampling_baseline - self.creation).as_millis(),
+                    )
+                    .as_bytes(),
+                );
+
+                let mut first = true;
+                let to_resolve = self.samples.len();
+                for (i, Sample(id, instant, stack)) in self.samples.drain(..).enumerate() {
+                    println!("Resolving {}/{}", i + 1, to_resolve);
+                    let profile = stack.to_hangprofile();
+                    let name = match self.component_names.get(&id) {
+                        Some(ref s) => format!("\"{}\"", s),
+                        None => format!("null"),
+                    };
+                    let json = format!(
+                        "{}{{ \"name\": {}, \"namespace\": {}, \"index\": {}, \"type\": \"{:?}\", \
+                         \"time\": {}, \"frames\": {} }}",
+                        if !first { ",\n" } else { "" },
+                        name,
+                        id.0.namespace_id.0,
+                        id.0.index.0.get(),
+                        id.1,
+                        (instant - self.sampling_baseline).as_millis(),
+                        serde_json::to_string(&profile.backtrace).unwrap(),
+                    );
+                    bytes.extend(json.as_bytes());
+                    first = false;
+                }
+
+                bytes.extend(b"\n] }");
+                let _ = self
+                    .constellation_chan
+                    .send(HangMonitorAlert::Profile(bytes));
+
+                *SAMPLING_STATE.lock().unwrap() = SamplerState::NotSampling;
+                self.sampling_duration = None;
+            },
+            _ => (),
         }
     }
 
     pub fn run(&mut self) -> bool {
+        self.handle_sampling();
+
+        let timeout = if let Some(duration) = self.sampling_duration {
+            duration
+                .checked_sub(Instant::now() - self.last_sample)
+                .unwrap_or_else(|| Duration::from_millis(0))
+        } else {
+            Duration::from_millis(100)
+        };
         let received = select! {
             recv(self.port) -> event => {
                 match event {
@@ -165,7 +273,7 @@ impl BackgroundHangMonitorWorker {
                     Err(_) => return false,
                 }
             },
-            recv(after(Duration::from_millis(100))) -> _ => None,
+            recv(after(timeout)) -> _ => None,
         };
         if let Some(msg) = received {
             self.handle_msg(msg);
@@ -175,7 +283,15 @@ impl BackgroundHangMonitorWorker {
                 self.handle_msg(another_msg);
             }
         }
-        self.perform_a_hang_monitor_checkpoint();
+
+        if let Some(duration) = self.sampling_duration {
+            if Instant::now() - self.last_sample > duration {
+                self.sample();
+                self.last_sample = Instant::now();
+            }
+        } else {
+            self.perform_a_hang_monitor_checkpoint();
+        }
         true
     }
 
@@ -185,6 +301,7 @@ impl BackgroundHangMonitorWorker {
                 component_id,
                 MonitoredComponentMsg::Register(
                     sampler,
+                    name,
                     transient_hang_timeout,
                     permanent_hang_timeout,
                 ),
@@ -199,6 +316,9 @@ impl BackgroundHangMonitorWorker {
                     sent_permanent_alert: false,
                     is_waiting: true,
                 };
+                if let Some(name) = name {
+                    self.component_names.insert(component_id.clone(), name);
+                }
                 assert!(
                     self.monitored_components
                         .insert(component_id, component)
@@ -250,11 +370,13 @@ impl BackgroundHangMonitorWorker {
                     Ok(native_stack) => Some(native_stack.to_hangprofile()),
                     Err(()) => None,
                 };
-                let _ = self.constellation_chan.send(HangAlert::Permanent(
-                    component_id.clone(),
-                    last_annotation,
-                    profile,
-                ));
+                let _ = self
+                    .constellation_chan
+                    .send(HangMonitorAlert::Hang(HangAlert::Permanent(
+                        component_id.clone(),
+                        last_annotation,
+                        profile,
+                    )));
                 monitored.sent_permanent_alert = true;
                 continue;
             }
@@ -264,9 +386,23 @@ impl BackgroundHangMonitorWorker {
                 }
                 let _ = self
                     .constellation_chan
-                    .send(HangAlert::Transient(component_id.clone(), last_annotation));
+                    .send(HangMonitorAlert::Hang(HangAlert::Transient(
+                        component_id.clone(),
+                        last_annotation,
+                    )));
                 monitored.sent_transient_alert = true;
             }
         }
     }
+
+    fn sample(&mut self) {
+        for (component_id, monitored) in self.monitored_components.iter_mut() {
+            let instant = Instant::now();
+            if let Ok(stack) = monitored.sampler.suspend_and_sample_thread() {
+                // TODO: support a bounded buffer that discards older samples.
+                self.samples
+                    .push(Sample(component_id.clone(), instant, stack));
+            }
+        }
+    }
 }

components/background_hang_monitor/lib.rs

@@ -7,6 +7,8 @@
 #[macro_use]
 extern crate crossbeam_channel;
 #[macro_use]
+extern crate lazy_static;
+#[macro_use]
 extern crate log;
 
 pub mod background_hang_monitor;

components/compositing/windowing.rs

@@ -16,6 +16,7 @@ use servo_url::ServoUrl;
 use std::fmt::{Debug, Error, Formatter};
 #[cfg(feature = "gl")]
 use std::rc::Rc;
+use std::time::Duration;
 use style_traits::DevicePixel;
 use webrender_api::{DeviceIntPoint, DeviceIntRect, DeviceIntSize, DevicePoint, ScrollLocation};
 use webvr::VRServiceManager;
@@ -91,6 +92,8 @@ pub enum WindowEvent {
     ToggleWebRenderDebug(WebRenderDebugOption),
     /// Capture current WebRender
     CaptureWebRender,
+    /// Toggle sampling profiler with the given sampling rate
+    ToggleSamplingProfiler(Duration),
 }
 
 impl Debug for WindowEvent {
@@ -118,6 +121,7 @@ impl Debug for WindowEvent {
             WindowEvent::SelectBrowser(..) => write!(f, "SelectBrowser"),
             WindowEvent::ToggleWebRenderDebug(..) => write!(f, "ToggleWebRenderDebug"),
             WindowEvent::CaptureWebRender => write!(f, "CaptureWebRender"),
+            WindowEvent::ToggleSamplingProfiler(..) => write!(f, "ToggleSamplingProfiler"),
         }
     }
 }

components/constellation/constellation.rs

@@ -124,7 +124,7 @@ use keyboard_types::webdriver::Event as WebDriverInputEvent;
 use keyboard_types::KeyboardEvent;
 use layout_traits::LayoutThreadFactory;
 use log::{Level, LevelFilter, Log, Metadata, Record};
-use msg::constellation_msg::{BackgroundHangMonitorRegister, HangAlert};
+use msg::constellation_msg::{BackgroundHangMonitorRegister, HangMonitorAlert};
 use msg::constellation_msg::{
     BrowsingContextId, HistoryStateId, PipelineId, TopLevelBrowsingContextId,
 };
@@ -210,11 +210,11 @@ pub struct Constellation<Message, LTF, STF> {
 
     /// A channel for the background hang monitor to send messages
     /// to the constellation.
-    background_hang_monitor_sender: IpcSender<HangAlert>,
+    background_hang_monitor_sender: IpcSender<HangMonitorAlert>,
 
     /// A channel for the constellation to receiver messages
     /// from the background hang monitor.
-    background_hang_monitor_receiver: Receiver<Result<HangAlert, IpcError>>,
+    background_hang_monitor_receiver: Receiver<Result<HangMonitorAlert, IpcError>>,
 
     /// An IPC channel for layout threads to send messages to the constellation.
     /// This is the layout threads' view of `layout_receiver`.
@@ -942,7 +942,7 @@ where
         #[derive(Debug)]
         enum Request {
             Script((PipelineId, FromScriptMsg)),
-            BackgroundHangMonitor(HangAlert),
+            BackgroundHangMonitor(HangMonitorAlert),
             Compositor(FromCompositorMsg),
             Layout(FromLayoutMsg),
             NetworkListener((PipelineId, FetchResponseMsg)),
@@ -1008,10 +1008,17 @@ where
         }
     }
 
-    fn handle_request_from_background_hang_monitor(&self, message: HangAlert) {
-        // TODO: In case of a permanent hang being reported, add a "kill script" workflow,
-        // via the embedder?
-        warn!("Component hang alert: {:?}", message);
+    fn handle_request_from_background_hang_monitor(&self, message: HangMonitorAlert) {
+        match message {
+            HangMonitorAlert::Profile(bytes) => self
+                .embedder_proxy
+                .send((None, EmbedderMsg::ReportProfile(bytes))),
+            HangMonitorAlert::Hang(hang) => {
+                // TODO: In case of a permanent hang being reported, add a "kill script" workflow,
+                // via the embedder?
+                warn!("Component hang alert: {:?}", hang);
+            },
+        }
     }
 
     fn handle_request_from_network_listener(&mut self, message: (PipelineId, FetchResponseMsg)) {

components/constellation/pipeline.rs

@@ -18,7 +18,7 @@ use ipc_channel::Error;
 use layout_traits::LayoutThreadFactory;
 use metrics::PaintTimeMetrics;
 use msg::constellation_msg::TopLevelBrowsingContextId;
-use msg::constellation_msg::{BackgroundHangMonitorRegister, HangAlert};
+use msg::constellation_msg::{BackgroundHangMonitorRegister, HangMonitorAlert};
 use msg::constellation_msg::{BrowsingContextId, HistoryStateId, PipelineId, PipelineNamespaceId};
 use net::image_cache::ImageCacheImpl;
 use net_traits::image_cache::ImageCache;
@@ -122,7 +122,7 @@ pub struct InitialPipelineState {
     pub background_monitor_register: Option<Box<BackgroundHangMonitorRegister>>,
 
     /// A channel for the background hang monitor to send messages to the constellation.
-    pub background_hang_monitor_to_constellation_chan: IpcSender<HangAlert>,
+    pub background_hang_monitor_to_constellation_chan: IpcSender<HangMonitorAlert>,
 
     /// A channel for the layout thread to send messages to the constellation.
     pub layout_to_constellation_chan: IpcSender<LayoutMsg>,
@@ -467,7 +467,7 @@ pub struct UnprivilegedPipelineContent {
     parent_pipeline_id: Option<PipelineId>,
     opener: Option<BrowsingContextId>,
     script_to_constellation_chan: ScriptToConstellationChan,
-    background_hang_monitor_to_constellation_chan: IpcSender<HangAlert>,
+    background_hang_monitor_to_constellation_chan: IpcSender<HangMonitorAlert>,
     layout_to_constellation_chan: IpcSender<LayoutMsg>,
     scheduler_chan: IpcSender<TimerSchedulerMsg>,
     devtools_chan: Option<IpcSender<ScriptToDevtoolsControlMsg>>,
@@ -669,7 +669,7 @@ impl UnprivilegedPipelineContent {
         }
     }
 
-    pub fn background_hang_monitor_to_constellation_chan(&self) -> &IpcSender<HangAlert> {
+    pub fn background_hang_monitor_to_constellation_chan(&self) -> &IpcSender<HangMonitorAlert> {
         &self.background_hang_monitor_to_constellation_chan
     }
 

components/embedder_traits/lib.rs

@@ -160,6 +160,8 @@ pub enum EmbedderMsg {
     HideIME,
     /// Servo has shut down
     Shutdown,
+    /// Report a complete sampled profile
+    ReportProfile(Vec<u8>),
 }
 
 impl Debug for EmbedderMsg {
@@ -189,6 +191,7 @@ impl Debug for EmbedderMsg {
             EmbedderMsg::Shutdown => write!(f, "Shutdown"),
             EmbedderMsg::AllowOpeningBrowser(..) => write!(f, "AllowOpeningBrowser"),
             EmbedderMsg::BrowserCreated(..) => write!(f, "BrowserCreated"),
+            EmbedderMsg::ReportProfile(..) => write!(f, "ReportProfile"),
         }
     }
 }

components/msg/constellation_msg.rs

@@ -350,6 +350,24 @@ pub enum HangAnnotation {
     Script(ScriptHangAnnotation),
 }
 
+/// Hang-alerts are sent by the monitor to the constellation.
+#[derive(Deserialize, Serialize)]
+pub enum HangMonitorAlert {
+    /// A component hang has been detected.
+    Hang(HangAlert),
+    /// Report a completed sampled profile.
+    Profile(Vec<u8>),
+}
+
+impl fmt::Debug for HangMonitorAlert {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            HangMonitorAlert::Hang(..) => write!(fmt, "Hang"),
+            HangMonitorAlert::Profile(..) => write!(fmt, "Profile"),
+        }
+    }
+}
+
 /// Hang-alerts are sent by the monitor to the constellation.
 #[derive(Deserialize, Serialize)]
 pub enum HangAlert {

components/servo/lib.rs

@@ -406,6 +406,10 @@ where
                 }
             },
 
+            WindowEvent::ToggleSamplingProfiler(rate) => {
+                HangMonitorRegister::toggle(rate);
+            },
+
             WindowEvent::ToggleWebRenderDebug(option) => {
                 self.compositor.toggle_webrender_debug(option);
             },