xpcom/base/MemoryTelemetry.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */

#include "MemoryTelemetry.h"
#include "nsMemoryReporterManager.h"

#include "GCTelemetry.h"
#include "mozilla/ClearOnShutdown.h"
#include "mozilla/Result.h"
#include "mozilla/ResultExtensions.h"
#include "mozilla/Services.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/SimpleEnumerator.h"
#include "mozilla/Telemetry.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/dom/ContentParent.h"
#include "mozilla/dom/ScriptSettings.h"
#include "nsContentUtils.h"
#include "nsIBrowserDOMWindow.h"
#include "nsIDOMChromeWindow.h"
#include "nsIMemoryReporter.h"
#include "nsIWindowMediator.h"
#include "nsImportModule.h"
#include "nsNetCID.h"
#include "nsObserverService.h"
#include "nsReadableUtils.h"
#include "nsThreadUtils.h"
#include "nsXULAppAPI.h"
#include "xpcpublic.h"

#include <cstdlib>

using namespace mozilla;

using mozilla::dom::AutoJSAPI;
using mozilla::dom::ContentParent;

// Do not gather data more than once a minute (ms)
static constexpr uint32_t kTelemetryInterval = 60 * 1000;

static constexpr const char* kTopicCycleCollectorBegin =
    "cycle-collector-begin";

// How long to wait in millis for all the child memory reports to come in
static constexpr uint32_t kTotalMemoryCollectorTimeout = 200;

static Result<nsCOMPtr<mozIGCTelemetry>, nsresult> GetGCTelemetry() {
  nsresult rv;

  nsCOMPtr<mozIGCTelemetryJSM> jsm =
      do_ImportModule("resource://gre/modules/GCTelemetry.jsm", &rv);
  MOZ_TRY(rv);

  nsCOMPtr<mozIGCTelemetry> gcTelemetry;
  MOZ_TRY(jsm->GetGCTelemetry(getter_AddRefs(gcTelemetry)));

  return std::move(gcTelemetry);
}

namespace {

enum class PrevValue : uint32_t {
#ifdef XP_WIN
  LOW_MEMORY_EVENTS_VIRTUAL,
  LOW_MEMORY_EVENTS_COMMIT_SPACE,
  LOW_MEMORY_EVENTS_PHYSICAL,
#endif
#if defined(XP_LINUX) && !defined(ANDROID)
  PAGE_FAULTS_HARD,
#endif
  SIZE_,
};

}  // anonymous namespace

constexpr uint32_t kUninitialized = ~0;

static uint32_t gPrevValues[uint32_t(PrevValue::SIZE_)];

static uint32_t PrevValueIndex(Telemetry::HistogramID aId) {
  switch (aId) {
#ifdef XP_WIN
    case Telemetry::LOW_MEMORY_EVENTS_VIRTUAL:
      return uint32_t(PrevValue::LOW_MEMORY_EVENTS_VIRTUAL);
    case Telemetry::LOW_MEMORY_EVENTS_COMMIT_SPACE:
      return uint32_t(PrevValue::LOW_MEMORY_EVENTS_COMMIT_SPACE);
    case Telemetry::LOW_MEMORY_EVENTS_PHYSICAL:
      return uint32_t(PrevValue::LOW_MEMORY_EVENTS_PHYSICAL);
#endif
#if defined(XP_LINUX) && !defined(ANDROID)
    case Telemetry::PAGE_FAULTS_HARD:
      return uint32_t(PrevValue::PAGE_FAULTS_HARD);
#endif
    default:
      MOZ_ASSERT_UNREACHABLE("Unexpected histogram ID");
      return 0;
  }
}

NS_IMPL_ISUPPORTS(MemoryTelemetry, nsIObserver, nsISupportsWeakReference)

MemoryTelemetry::MemoryTelemetry()
    : mThreadPool(do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID)) {}

void MemoryTelemetry::Init() {
  for (auto& val : gPrevValues) {
    val = kUninitialized;
  }

  if (XRE_IsContentProcess()) {
    nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
    MOZ_RELEASE_ASSERT(obs);

    obs->AddObserver(this, "content-child-shutdown", true);
  }
}

/* static */ MemoryTelemetry& MemoryTelemetry::Get() {
  static RefPtr<MemoryTelemetry> sInstance;

  MOZ_ASSERT(NS_IsMainThread());

  if (!sInstance) {
    sInstance = new MemoryTelemetry();
    sInstance->Init();
    ClearOnShutdown(&sInstance);
  }
  return *sInstance;
}

nsresult MemoryTelemetry::DelayedInit() {
  if (Telemetry::CanRecordExtended()) {
    nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
    MOZ_RELEASE_ASSERT(obs);

    obs->AddObserver(this, kTopicCycleCollectorBegin, true);
  }

  GatherReports();

  if (Telemetry::CanRecordExtended()) {
    nsCOMPtr<mozIGCTelemetry> gcTelemetry;
    MOZ_TRY_VAR(gcTelemetry, GetGCTelemetry());

    MOZ_TRY(gcTelemetry->Init());
  }

  return NS_OK;
}

nsresult MemoryTelemetry::Shutdown() {
  nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
  MOZ_RELEASE_ASSERT(obs);

  obs->RemoveObserver(this, kTopicCycleCollectorBegin);

  if (Telemetry::CanRecordExtended()) {
    nsCOMPtr<mozIGCTelemetry> gcTelemetry;
    MOZ_TRY_VAR(gcTelemetry, GetGCTelemetry());

    MOZ_TRY(gcTelemetry->Shutdown());
  }

  return NS_OK;
}

static inline void HandleMemoryReport(Telemetry::HistogramID aId,
                                      int32_t aUnits, uint64_t aAmount,
                                      const nsCString& aKey = VoidCString()) {
  uint32_t val;
  switch (aUnits) {
    case nsIMemoryReporter::UNITS_BYTES:
      val = uint32_t(aAmount / 1024);
      break;

    case nsIMemoryReporter::UNITS_PERCENTAGE:
      // UNITS_PERCENTAGE amounts are 100x greater than their raw value.
      val = uint32_t(aAmount / 100);
      break;

    case nsIMemoryReporter::UNITS_COUNT:
      val = uint32_t(aAmount);
      break;

    case nsIMemoryReporter::UNITS_COUNT_CUMULATIVE: {
      // If the reporter gives us a cumulative count, we'll report the
      // difference in its value between now and our previous ping.

      uint32_t idx = PrevValueIndex(aId);
      uint32_t prev = gPrevValues[idx];
      gPrevValues[idx] = aAmount;

      if (prev == kUninitialized) {
        // If this is the first time we're reading this reporter, store its
        // current value but don't report it in the telemetry ping, so we
        // ignore the effect startup had on the reporter.
        return;
      }
      val = aAmount - prev;
      break;
    }

    default:
      MOZ_ASSERT_UNREACHABLE("Unexpected aUnits value");
      return;
  }

  // Note: The reference equality check here should allow the compiler to
  // optimize this case out at compile time when we weren't given a key,
  // while IsEmpty() or IsVoid() most likely will not.
  if (&aKey == &VoidCString()) {
    Telemetry::Accumulate(aId, val);
  } else {
    Telemetry::Accumulate(aId, aKey, val);
  }
}

nsresult MemoryTelemetry::GatherReports(
    const std::function<void()>& aCompletionCallback) {
  auto cleanup = MakeScopeExit([&]() {
    if (aCompletionCallback) {
      aCompletionCallback();
    }
  });

  RefPtr<nsMemoryReporterManager> mgr = nsMemoryReporterManager::GetOrCreate();
  MOZ_DIAGNOSTIC_ASSERT(mgr);
  NS_ENSURE_TRUE(mgr, NS_ERROR_FAILURE);

#define RECORD(id, metric, units)                                       \
  do {                                                                  \
    int64_t amt;                                                        \
    nsresult rv = mgr->Get##metric(&amt);                               \
    if (NS_SUCCEEDED(rv)) {                                             \
      HandleMemoryReport(Telemetry::id, nsIMemoryReporter::units, amt); \
    } else if (rv != NS_ERROR_NOT_AVAILABLE) {                          \
      NS_WARNING("Failed to retrieve memory telemetry for " #metric);   \
    }                                                                   \
  } while (0)

  // GHOST_WINDOWS is opt-out as of Firefox 55
  RECORD(GHOST_WINDOWS, GhostWindows, UNITS_COUNT);

  // If we're running in the parent process, collect data from all processes for
  // the MEMORY_TOTAL histogram.
  if (XRE_IsParentProcess() && !mTotalMemoryGatherer) {
    mTotalMemoryGatherer = new TotalMemoryGatherer();
    mTotalMemoryGatherer->Begin(mThreadPool);
  }

  if (!Telemetry::CanRecordReleaseData()) {
    return NS_OK;
  }

  // Get memory measurements from distinguished amount attributes.  We used
  // to measure "explicit" too, but it could cause hangs, and the data was
  // always really noisy anyway.  See bug 859657.
  //
  // test_TelemetrySession.js relies on some of these histograms being
  // here.  If you remove any of the following histograms from here, you'll
  // have to modify test_TelemetrySession.js:
  //
  //   * MEMORY_TOTAL,
  //   * MEMORY_JS_GC_HEAP, and
  //   * MEMORY_JS_COMPARTMENTS_SYSTEM.
  //
  // The distinguished amount attribute names don't match the telemetry id
  // names in some cases due to a combination of (a) historical reasons, and
  // (b) the fact that we can't change telemetry id names without breaking
  // data continuity.

  // Collect cheap or main-thread only metrics synchronously, on the main
  // thread.
  RECORD(MEMORY_JS_GC_HEAP, JSMainRuntimeGCHeap, UNITS_BYTES);
  RECORD(MEMORY_JS_COMPARTMENTS_SYSTEM, JSMainRuntimeCompartmentsSystem,
         UNITS_COUNT);
  RECORD(MEMORY_JS_COMPARTMENTS_USER, JSMainRuntimeCompartmentsUser,
         UNITS_COUNT);
  RECORD(MEMORY_JS_REALMS_SYSTEM, JSMainRuntimeRealmsSystem, UNITS_COUNT);
  RECORD(MEMORY_JS_REALMS_USER, JSMainRuntimeRealmsUser, UNITS_COUNT);
  RECORD(MEMORY_IMAGES_CONTENT_USED_UNCOMPRESSED, ImagesContentUsedUncompressed,
         UNITS_BYTES);
  RECORD(MEMORY_STORAGE_SQLITE, StorageSQLite, UNITS_BYTES);
#ifdef XP_WIN
  RECORD(LOW_MEMORY_EVENTS_VIRTUAL, LowMemoryEventsVirtual,
         UNITS_COUNT_CUMULATIVE);
  RECORD(LOW_MEMORY_EVENTS_COMMIT_SPACE, LowMemoryEventsCommitSpace,
         UNITS_COUNT_CUMULATIVE);
  RECORD(LOW_MEMORY_EVENTS_PHYSICAL, LowMemoryEventsPhysical,
         UNITS_COUNT_CUMULATIVE);
#endif
#if defined(XP_LINUX) && !defined(ANDROID)
  RECORD(PAGE_FAULTS_HARD, PageFaultsHard, UNITS_COUNT_CUMULATIVE);
#endif

  RefPtr<Runnable> completionRunnable;
  if (aCompletionCallback) {
    completionRunnable = NS_NewRunnableFunction(__func__, aCompletionCallback);
  }

  // Collect expensive metrics that can be calculated off-main-thread
  // asynchronously, on a background thread.
  RefPtr<Runnable> runnable = NS_NewRunnableFunction(
      "MemoryTelemetry::GatherReports", [mgr, completionRunnable]() mutable {
        RECORD(MEMORY_VSIZE, Vsize, UNITS_BYTES);
#if !defined(HAVE_64BIT_BUILD) || !defined(XP_WIN)
        RECORD(MEMORY_VSIZE_MAX_CONTIGUOUS, VsizeMaxContiguous, UNITS_BYTES);
#endif
        RECORD(MEMORY_RESIDENT_FAST, ResidentFast, UNITS_BYTES);
        RECORD(MEMORY_RESIDENT_PEAK, ResidentPeak, UNITS_BYTES);
        RECORD(MEMORY_UNIQUE, ResidentUnique, UNITS_BYTES);
        RECORD(MEMORY_HEAP_ALLOCATED, HeapAllocated, UNITS_BYTES);
        RECORD(MEMORY_HEAP_OVERHEAD_FRACTION, HeapOverheadFraction,
               UNITS_PERCENTAGE);

        if (completionRunnable) {
          NS_DispatchToMainThread(completionRunnable.forget(),
                                  NS_DISPATCH_NORMAL);
        }
      });

#undef RECORD

  nsresult rv = mThreadPool->Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
  if (!NS_WARN_IF(NS_FAILED(rv))) {
    cleanup.release();
  }

  return NS_OK;
}

NS_IMPL_ISUPPORTS(MemoryTelemetry::TotalMemoryGatherer, nsITimerCallback)

/**
 * Polls all child processes for their unique set size, and populates the
 * MEMORY_TOTAL and MEMORY_DISTRIBUTION_AMONG_CONTENT histograms with the
 * results.
 */
void MemoryTelemetry::TotalMemoryGatherer::Begin(nsIEventTarget* aThreadPool) {
  nsCOMPtr<nsISerialEventTarget> target = GetMainThreadSerialEventTarget();

  nsTArray<ContentParent*> parents;
  ContentParent::GetAll(parents);
  for (auto& parent : parents) {
    mRemainingChildCount++;
    parent->SendGetMemoryUniqueSetSize()->Then(
        target, "TotalMemoryGather::Begin", this,
        &TotalMemoryGatherer::CollectResult, &TotalMemoryGatherer::OnFailure);
  }

  mChildSizes.SetCapacity(mRemainingChildCount);

  RefPtr<TotalMemoryGatherer> self{this};

  aThreadPool->Dispatch(
      NS_NewRunnableFunction(
          "TotalMemoryGather::Begin",
          [self]() {
            RefPtr<nsMemoryReporterManager> mgr =
                nsMemoryReporterManager::GetOrCreate();
            MOZ_RELEASE_ASSERT(mgr);

            NS_DispatchToMainThread(NewRunnableMethod<int64_t>(
                "TotalMemoryGather::CollectParentSize", self,
                &TotalMemoryGatherer::CollectParentSize, mgr->ResidentFast()));
          }),
      NS_DISPATCH_NORMAL);

  NS_NewTimerWithCallback(getter_AddRefs(mTimeout), this,
                          kTotalMemoryCollectorTimeout,
                          nsITimer::TYPE_ONE_SHOT);
}

nsresult MemoryTelemetry::TotalMemoryGatherer::MaybeFinish() {
  // If we timed out waiting for a response from any child, we don't report
  // anything for this attempt.
  if (!mTimeout || !mHaveParentSize || mRemainingChildCount) {
    return NS_OK;
  }

  mTimeout = nullptr;
  MemoryTelemetry::Get().mTotalMemoryGatherer = nullptr;

  HandleMemoryReport(Telemetry::MEMORY_TOTAL, nsIMemoryReporter::UNITS_BYTES,
                     mTotalMemory);

  if (mChildSizes.Length() > 1) {
    int32_t tabsCount;
    MOZ_TRY_VAR(tabsCount, GetOpenTabsCount());

    nsCString key;
    if (tabsCount <= 10) {
      key = "0 - 10 tabs";
    } else if (tabsCount <= 500) {
      key = "11 - 500 tabs";
    } else {
      key = "more tabs";
    }

    // Mean of the USS of all the content processes.
    int64_t mean = 0;
    for (auto size : mChildSizes) {
      mean += size;
    }
    mean /= mChildSizes.Length();

    // For some users, for unknown reasons (though most likely because they're
    // in a sandbox without procfs mounted), we wind up with 0 here, which
    // triggers a floating point exception if we try to calculate values using
    // it.
    if (!mean) {
      return NS_ERROR_UNEXPECTED;
    }

    // Absolute error of USS for each content process, normalized by the mean
    // (*100 to get it in percentage). 20% means for a content process that it
    // is using 20% more or 20% less than the mean.
    for (auto size : mChildSizes) {
      int64_t diff = llabs(size - mean) * 100 / mean;

      HandleMemoryReport(Telemetry::MEMORY_DISTRIBUTION_AMONG_CONTENT,
                         nsIMemoryReporter::UNITS_COUNT, diff, key);
    }
  }

  // This notification is for testing only.
  if (nsCOMPtr<nsIObserverService> obs = services::GetObserverService()) {
    obs->NotifyObservers(nullptr, "gather-memory-telemetry-finished", nullptr);
  }

  return NS_OK;
}

void MemoryTelemetry::TotalMemoryGatherer::CollectParentSize(
    int64_t aResident) {
  mTotalMemory += aResident;
  mHaveParentSize = true;

  MaybeFinish();
}

void MemoryTelemetry::TotalMemoryGatherer::CollectResult(int64_t aChildUSS) {
  mChildSizes.AppendElement(aChildUSS);

  mTotalMemory += aChildUSS;
  mRemainingChildCount--;

  MaybeFinish();
}

void MemoryTelemetry::TotalMemoryGatherer::OnFailure(
    mozilla::ipc::ResponseRejectReason aReason) {
  // Treat failure of any request the same as a timeout.
  Notify(nullptr);
}

nsresult MemoryTelemetry::TotalMemoryGatherer::Notify(nsITimer* aTimer) {
  // Set mTimeout null to indicate the timeout has fired. After this, all
  // results for this attempt will be ignored.
  mTimeout = nullptr;
  MemoryTelemetry::Get().mTotalMemoryGatherer = nullptr;
  return NS_OK;
}

/* static */ Result<uint32_t, nsresult> MemoryTelemetry::GetOpenTabsCount() {
  nsresult rv;

  nsCOMPtr<nsIWindowMediator> windowMediator(
      do_GetService(NS_WINDOWMEDIATOR_CONTRACTID, &rv));
  MOZ_TRY(rv);

  nsCOMPtr<nsISimpleEnumerator> enumerator;
  MOZ_TRY(windowMediator->GetEnumerator(u"navigator:browser",
                                        getter_AddRefs(enumerator)));

  uint32_t total = 0;
  for (auto& window : SimpleEnumerator<nsIDOMChromeWindow>(enumerator)) {
    nsCOMPtr<nsIBrowserDOMWindow> browserWin;
    MOZ_TRY(window->GetBrowserDOMWindow(getter_AddRefs(browserWin)));

    NS_ENSURE_TRUE(browserWin, Err(NS_ERROR_UNEXPECTED));

    uint32_t tabCount;
    MOZ_TRY(browserWin->GetTabCount(&tabCount));
    total += tabCount;
  }

  return total;
}

void MemoryTelemetry::GetUniqueSetSize(
    std::function<void(const int64_t&)>&& aCallback) {
  mThreadPool->Dispatch(
      NS_NewRunnableFunction(
          "MemoryTelemetry::GetUniqueSetSize",
          [callback = std::move(aCallback)]() mutable {
            RefPtr<nsMemoryReporterManager> mgr =
                nsMemoryReporterManager::GetOrCreate();
            MOZ_RELEASE_ASSERT(mgr);

            int64_t uss = mgr->ResidentUnique();

            NS_DispatchToMainThread(NS_NewRunnableFunction(
                "MemoryTelemetry::GetUniqueSetSizeResult",
                [uss, callback = std::move(callback)]() { callback(uss); }));
          }),
      NS_DISPATCH_NORMAL);
}

nsresult MemoryTelemetry::Observe(nsISupports* aSubject, const char* aTopic,
                                  const char16_t* aData) {
  if (strcmp(aTopic, kTopicCycleCollectorBegin) == 0) {
    auto now = TimeStamp::Now();
    if (!mLastPoll.IsNull() &&
        (now - mLastPoll).ToMilliseconds() < kTelemetryInterval) {
      return NS_OK;
    }

    mLastPoll = now;

    NS_DispatchToCurrentThreadQueue(
        NewRunnableMethod<std::function<void()>>(
            "MemoryTelemetry::GatherReports", this,
            &MemoryTelemetry::GatherReports, nullptr),
        EventQueuePriority::Idle);
  } else if (strcmp(aTopic, "content-child-shutdown") == 0) {
    if (nsCOMPtr<nsITelemetry> telemetry =
            do_GetService("@mozilla.org/base/telemetry;1")) {
      telemetry->FlushBatchedChildTelemetry();
    }
  }
  return NS_OK;
}