The Tor Browser: toolkit/xre/EventTracer.cpp@6474c204b198 (annotated)

toolkit/xre/EventTracer.cpp@6474c204b198 (annotated)

toolkit/xre/EventTracer.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 /*
  * Event loop instrumentation. This code attempts to measure the
  * latency of the UI-thread event loop by firing native events at it from
  * a background thread, and measuring how long it takes for them
  * to be serviced. The measurement interval (kMeasureInterval, below)
  * is also used as the upper bound of acceptable response time.
  * When an event takes longer than that interval to be serviced,
  * a sample will be written to the log.
  *
  * Usage:
  *
  * Set MOZ_INSTRUMENT_EVENT_LOOP=1 in the environment to enable
  * this instrumentation. Currently only the UI process is instrumented.
  *
  * Set MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT in the environment to a
  * file path to contain the log output, the default is to log to stdout.
  *
  * Set MOZ_INSTRUMENT_EVENT_LOOP_THRESHOLD in the environment to an
  * integer number of milliseconds to change the threshold for reporting.
  * The default is 20 milliseconds. Unresponsive periods shorter than this
  * threshold will not be reported.
  *
  * Set MOZ_INSTRUMENT_EVENT_LOOP_INTERVAL in the environment to an
  * integer number of milliseconds to change the maximum sampling frequency.
  * This variable controls how often events will be sent to the main
  * thread's event loop to sample responsiveness. The sampler will not
  * send events twice within LOOP_INTERVAL milliseconds.
  * The default is 10 milliseconds.
  *
  * All logged output lines start with MOZ_EVENT_TRACE. All timestamps
  * output are milliseconds since the epoch (PRTime / 1000).
  *
  * On startup, a line of the form:
  *   MOZ_EVENT_TRACE start <timestamp>
  * will be output.
  *
  * On shutdown, a line of the form:
  *   MOZ_EVENT_TRACE stop <timestamp>
  * will be output.
  *
  * When an event servicing time exceeds the threshold, a line of the form:
  *   MOZ_EVENT_TRACE sample <timestamp> <duration>
  * will be output, where <duration> is the number of milliseconds that
  * it took for the event to be serviced. Duration may contain a fractional
  * component.
  */
 #include "GeckoProfiler.h"
 #include "EventTracer.h"
 #include <stdio.h>
 #include "mozilla/Preferences.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/WidgetTraceEvent.h"
 #include "nsDebug.h"
 #include <limits.h>
 #include <prenv.h>
 #include <prinrval.h>
 #include <prthread.h>
 #include <prtime.h>
 #ifdef MOZ_WIDGET_GONK
 #include "nsThreadUtils.h"
 #include "nsIObserverService.h"
 #include "mozilla/Services.h"
 #endif
 using mozilla::TimeDuration;
 using mozilla::TimeStamp;
 using mozilla::FireAndWaitForTracerEvent;
 namespace {
 PRThread* sTracerThread = nullptr;
 bool sExit = false;
 struct TracerStartClosure {
   bool mLogTracing;
   int32_t mThresholdInterval;
 };
 #ifdef MOZ_WIDGET_GONK
 class EventLoopLagDispatcher : public nsRunnable
 {
   public:
     explicit EventLoopLagDispatcher(int aLag)
       : mLag(aLag) {}
     NS_IMETHODIMP Run()
     {
       nsCOMPtr<nsIObserverService> obsService =
         mozilla::services::GetObserverService();
       if (!obsService) {
         return NS_ERROR_FAILURE;
       }
       nsAutoString value;
       value.AppendInt(mLag);
       return obsService->NotifyObservers(nullptr, "event-loop-lag", value.get());
     }
   private:
     int mLag;
 };
 #endif
 /*
  * The tracer thread fires events at the native event loop roughly
  * every kMeasureInterval. It will sleep to attempt not to send them
  * more quickly, but if the response time is longer than kMeasureInterval
  * it will not send another event until the previous response is received.
  *
  * The output defaults to stdout, but can be redirected to a file by
  * settting the environment variable MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT
  * to the name of a file to use.
  */
 void TracerThread(void *arg)
 {
   PR_SetCurrentThreadName("Event Tracer");
   TracerStartClosure* threadArgs = static_cast<TracerStartClosure*>(arg);
   // These are the defaults. They can be overridden by environment vars.
   // This should be set to the maximum latency we'd like to allow
   // for responsiveness.
   int32_t thresholdInterval = threadArgs->mThresholdInterval;
   PRIntervalTime threshold = PR_MillisecondsToInterval(thresholdInterval);
   // This is the sampling interval.
   PRIntervalTime interval = PR_MillisecondsToInterval(thresholdInterval / 2);
   sExit = false;
   FILE* log = nullptr;
   char* envfile = PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP_OUTPUT");
   if (envfile) {
     log = fopen(envfile, "w");
   }
   if (log == nullptr)
     log = stdout;
   char* thresholdenv = PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP_THRESHOLD");
   if (thresholdenv && *thresholdenv) {
     int val = atoi(thresholdenv);
     if (val != 0 && val != INT_MAX && val != INT_MIN) {
       threshold = PR_MillisecondsToInterval(val);
     }
   }
   char* intervalenv = PR_GetEnv("MOZ_INSTRUMENT_EVENT_LOOP_INTERVAL");
   if (intervalenv && *intervalenv) {
     int val = atoi(intervalenv);
     if (val != 0 && val != INT_MAX && val != INT_MIN) {
       interval = PR_MillisecondsToInterval(val);
     }
   }
   if (threadArgs->mLogTracing) {
     long long now = PR_Now() / PR_USEC_PER_MSEC;
     fprintf(log, "MOZ_EVENT_TRACE start %llu\n", now);
   }
   while (!sExit) {
     TimeStamp start(TimeStamp::Now());
     profiler_responsiveness(start);
     PRIntervalTime next_sleep = interval;
     //TODO: only wait up to a maximum of interval; return
     // early if that threshold is exceeded and dump a stack trace
     // or do something else useful.
     if (FireAndWaitForTracerEvent()) {
       TimeDuration duration = TimeStamp::Now() - start;
       // Only report samples that exceed our measurement threshold.
       long long now = PR_Now() / PR_USEC_PER_MSEC;
       if (threadArgs->mLogTracing && duration.ToMilliseconds() > threshold) {
         fprintf(log, "MOZ_EVENT_TRACE sample %llu %lf\n",
                 now,
                 duration.ToMilliseconds());
 #ifdef MOZ_WIDGET_GONK
         NS_DispatchToMainThread(
          new EventLoopLagDispatcher(int(duration.ToSecondsSigDigits() * 1000)));
 #endif
       }
       if (next_sleep > duration.ToMilliseconds()) {
         next_sleep -= int(duration.ToMilliseconds());
       }
       else {
         // Don't sleep at all if this event took longer than the measure
         // interval to deliver.
         next_sleep = 0;
       }
     }
     if (next_sleep != 0 && !sExit) {
       PR_Sleep(next_sleep);
     }
   }
   if (threadArgs->mLogTracing) {
     long long now = PR_Now() / PR_USEC_PER_MSEC;
     fprintf(log, "MOZ_EVENT_TRACE stop %llu\n", now);
   }
   if (log != stdout)
     fclose(log);
   delete threadArgs;
 }
 } // namespace
 namespace mozilla {
 bool InitEventTracing(bool aLog)
 {
   if (sTracerThread)
     return true;
   // Initialize the widget backend.
   if (!InitWidgetTracing())
     return false;
   // The tracer thread owns the object and will delete it.
   TracerStartClosure* args = new TracerStartClosure();
   args->mLogTracing = aLog;
   // Pass the default threshold interval.
   int32_t thresholdInterval = 20;
   Preferences::GetInt("devtools.eventlooplag.threshold", &thresholdInterval);
   args->mThresholdInterval = thresholdInterval;
   // Create a thread that will fire events back at the
   // main thread to measure responsiveness.
   NS_ABORT_IF_FALSE(!sTracerThread, "Event tracing already initialized!");
   sTracerThread = PR_CreateThread(PR_USER_THREAD,
                                   TracerThread,
                                   args,
                                   PR_PRIORITY_NORMAL,
                                   PR_GLOBAL_THREAD,
                                   PR_JOINABLE_THREAD,
 );
   return sTracerThread != nullptr;
 }
 void ShutdownEventTracing()
 {
   if (!sTracerThread)
     return;
   sExit = true;
   // Ensure that the tracer thread doesn't hang.
   SignalTracerThread();
   if (sTracerThread)
     PR_JoinThread(sTracerThread);
   sTracerThread = nullptr;
   // Allow the widget backend to clean up.
   CleanUpWidgetTracing();
 }
 }  // namespace mozilla

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toolkit/xre/EventTracer.cpp@6474c204b198 (annotated)

toolkit/xre/EventTracer.cpp