tools/profiler/core/ProfilerBacktrace.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef __PROFILER_BACKTRACE_H
   8 #define __PROFILER_BACKTRACE_H
   9
  10 #include "ProfileBuffer.h"
  11
  12 #include "mozilla/ProfileBufferEntrySerialization.h"
  13 #include "mozilla/UniquePtrExtensions.h"
  14
  15 #include <string>
  16
  17 class ProfileBuffer;
  18 class ProfilerCodeAddressService;
  19 class ThreadInfo;
  20 class UniqueStacks;
  21
  22 namespace mozilla {
  23 class ProfileChunkedBuffer;
  24 class TimeStamp;
  25 namespace baseprofiler {
  26 class SpliceableJSONWriter;
  27 }  // namespace baseprofiler
  28 }  // namespace mozilla
  29
  30 // ProfilerBacktrace encapsulates a synchronous sample.
  31 // It can work with a ProfileBuffer and/or a ProfileChunkedBuffer (if both, they
  32 // must already be linked together). The ProfileChunkedBuffer contains all the
  33 // data; the ProfileBuffer is not strictly needed, only provide it if it is
  34 // already available at the call site.
  35 // And these buffers can either be:
  36 // - owned here, so that the ProfilerBacktrace object can be kept for later
  37 //   use), OR
  38 // - referenced through pointers (in cases where the backtrace is immediately
  39 //   streamed out, so we only need temporary references to external buffers);
  40 //   these pointers may be null for empty backtraces.
  41 class ProfilerBacktrace {
  42  public:
  43   // Take ownership of external buffers and use them to keep, and to stream a
  44   // backtrace. If a ProfileBuffer is given, its underlying chunked buffer must
  45   // be provided as well.
  46   explicit ProfilerBacktrace(
  47       const char* aName,
  48       mozilla::UniquePtr<mozilla::ProfileChunkedBuffer>
  49           aProfileChunkedBufferStorage,
  50       mozilla::UniquePtr<ProfileBuffer> aProfileBufferStorageOrNull = nullptr);
  51
  52   // Take pointers to external buffers and use them to stream a backtrace.
  53   // If null, the backtrace is effectively empty.
  54   // If both are provided, they must already be connected.
  55   explicit ProfilerBacktrace(
  56       const char* aName,
  57       mozilla::ProfileChunkedBuffer* aExternalProfileChunkedBufferOrNull =
  58           nullptr,
  59       ProfileBuffer* aExternalProfileBufferOrNull = nullptr);
  60
  61   ~ProfilerBacktrace();
  62
  63   [[nodiscard]] bool IsEmpty() const {
  64     return !mProfileChunkedBuffer ||
  65            mozilla::ProfileBufferEntryWriter::Serializer<
  66                mozilla::ProfileChunkedBuffer>::Bytes(*mProfileChunkedBuffer) <=
  67                mozilla::ULEB128Size(0u);
  68   }
  69
  70   // ProfilerBacktraces' stacks are deduplicated in the context of the
  71   // profile that contains the backtrace as a marker payload.
  72   //
  73   // That is, markers that contain backtraces should not need their own stack,
  74   // frame, and string tables. They should instead reuse their parent
  75   // profile's tables.
  76   ProfilerThreadId StreamJSON(
  77       mozilla::baseprofiler::SpliceableJSONWriter& aWriter,
  78       const mozilla::TimeStamp& aProcessStartTime, UniqueStacks& aUniqueStacks);
  79
  80  private:
  81   // Used to serialize a ProfilerBacktrace.
  82   friend struct mozilla::ProfileBufferEntryWriter::Serializer<
  83       ProfilerBacktrace>;
  84   friend struct mozilla::ProfileBufferEntryReader::Deserializer<
  85       ProfilerBacktrace>;
  86
  87   std::string mName;
  88
  89   // `ProfileChunkedBuffer` in which `mProfileBuffer` stores its data; must be
  90   // located before `mProfileBuffer` so that it's destroyed after.
  91   mozilla::UniquePtr<mozilla::ProfileChunkedBuffer>
  92       mOptionalProfileChunkedBufferStorage;
  93   // If null, there is no need to check mProfileBuffer's (if present) underlying
  94   // buffer because this is done when constructed.
  95   mozilla::ProfileChunkedBuffer* mProfileChunkedBuffer;
  96
  97   mozilla::UniquePtr<ProfileBuffer> mOptionalProfileBufferStorage;
  98   ProfileBuffer* mProfileBuffer;
  99 };
 100
 101 namespace mozilla {
 102
 103 // Format: [ UniquePtr<BlockRingsBuffer> | name ]
 104 // Initial len==0 marks a nullptr or empty backtrace.
 105 template <>
 106 struct mozilla::ProfileBufferEntryWriter::Serializer<ProfilerBacktrace> {
 107   static Length Bytes(const ProfilerBacktrace& aBacktrace) {
 108     if (!aBacktrace.mProfileChunkedBuffer) {
 109       // No buffer.
 110       return ULEB128Size(0u);
 111     }
 112     auto bufferBytes = SumBytes(*aBacktrace.mProfileChunkedBuffer);
 113     if (bufferBytes <= ULEB128Size(0u)) {
 114       // Empty buffer.
 115       return ULEB128Size(0u);
 116     }
 117     return bufferBytes + SumBytes(aBacktrace.mName);
 118   }
 119
 120   static void Write(mozilla::ProfileBufferEntryWriter& aEW,
 121                     const ProfilerBacktrace& aBacktrace) {
 122     if (!aBacktrace.mProfileChunkedBuffer ||
 123         SumBytes(*aBacktrace.mProfileChunkedBuffer) <= ULEB128Size(0u)) {
 124       // No buffer, or empty buffer.
 125       aEW.WriteULEB128(0u);
 126       return;
 127     }
 128     aEW.WriteObject(*aBacktrace.mProfileChunkedBuffer);
 129     aEW.WriteObject(aBacktrace.mName);
 130   }
 131 };
 132
 133 template <typename Destructor>
 134 struct mozilla::ProfileBufferEntryWriter::Serializer<
 135     mozilla::UniquePtr<ProfilerBacktrace, Destructor>> {
 136   static Length Bytes(
 137       const mozilla::UniquePtr<ProfilerBacktrace, Destructor>& aBacktrace) {
 138     if (!aBacktrace) {
 139       // Null backtrace pointer (treated like an empty backtrace).
 140       return ULEB128Size(0u);
 141     }
 142     return SumBytes(*aBacktrace);
 143   }
 144
 145   static void Write(
 146       mozilla::ProfileBufferEntryWriter& aEW,
 147       const mozilla::UniquePtr<ProfilerBacktrace, Destructor>& aBacktrace) {
 148     if (!aBacktrace) {
 149       // Null backtrace pointer (treated like an empty backtrace).
 150       aEW.WriteULEB128(0u);
 151       return;
 152     }
 153     aEW.WriteObject(*aBacktrace);
 154   }
 155 };
 156
 157 template <typename Destructor>
 158 struct mozilla::ProfileBufferEntryReader::Deserializer<
 159     mozilla::UniquePtr<ProfilerBacktrace, Destructor>> {
 160   static void ReadInto(
 161       mozilla::ProfileBufferEntryReader& aER,
 162       mozilla::UniquePtr<ProfilerBacktrace, Destructor>& aBacktrace) {
 163     aBacktrace = Read(aER);
 164   }
 165
 166   static mozilla::UniquePtr<ProfilerBacktrace, Destructor> Read(
 167       mozilla::ProfileBufferEntryReader& aER) {
 168     auto profileChunkedBuffer =
 169         aER.ReadObject<UniquePtr<ProfileChunkedBuffer>>();
 170     if (!profileChunkedBuffer) {
 171       return nullptr;
 172     }
 173     MOZ_ASSERT(
 174         !profileChunkedBuffer->IsThreadSafe(),
 175         "ProfilerBacktrace only stores non-thread-safe ProfileChunkedBuffers");
 176     std::string name = aER.ReadObject<std::string>();
 177     return UniquePtr<ProfilerBacktrace, Destructor>{
 178         new ProfilerBacktrace(name.c_str(), std::move(profileChunkedBuffer))};
 179   }
 180 };
 181
 182 }  // namespace mozilla
 183
 184 #endif  // __PROFILER_BACKTRACE_H