lib/XRay/Profile.cpp

   1 //===- Profile.cpp - XRay Profile Abstraction -----------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Defines the XRay Profile class representing the latency profile generated by
  10 // XRay's profiling mode.
  11 //
  12 //===----------------------------------------------------------------------===//
  13 #include "llvm/XRay/Profile.h"
  14
  15 #include "llvm/Support/DataExtractor.h"
  16 #include "llvm/Support/Error.h"
  17 #include "llvm/Support/FileSystem.h"
  18 #include "llvm/XRay/Trace.h"
  19 #include <deque>
  20 #include <memory>
  21
  22 namespace llvm {
  23 namespace xray {
  24
  25 Profile::Profile(const Profile &O) {
  26   // We need to re-create all the tries from the original (O), into the current
  27   // Profile being initialized, through the Block instances we see.
  28   for (const auto &Block : O) {
  29     Blocks.push_back({Block.Thread, {}});
  30     auto &B = Blocks.back();
  31     for (const auto &PathData : Block.PathData)
  32       B.PathData.push_back({internPath(cantFail(O.expandPath(PathData.first))),
  33                             PathData.second});
  34   }
  35 }
  36
  37 Profile &Profile::operator=(const Profile &O) {
  38   Profile P = O;
  39   *this = std::move(P);
  40   return *this;
  41 }
  42
  43 namespace {
  44
  45 struct BlockHeader {
  46   uint32_t Size;
  47   uint32_t Number;
  48   uint64_t Thread;
  49 };
  50
  51 static Expected<BlockHeader> readBlockHeader(DataExtractor &Extractor,
  52                                              uint32_t &Offset) {
  53   BlockHeader H;
  54   uint32_t CurrentOffset = Offset;
  55   H.Size = Extractor.getU32(&Offset);
  56   if (Offset == CurrentOffset)
  57     return make_error<StringError>(
  58         Twine("Error parsing block header size at offset '") +
  59             Twine(CurrentOffset) + "'",
  60         std::make_error_code(std::errc::invalid_argument));
  61   CurrentOffset = Offset;
  62   H.Number = Extractor.getU32(&Offset);
  63   if (Offset == CurrentOffset)
  64     return make_error<StringError>(
  65         Twine("Error parsing block header number at offset '") +
  66             Twine(CurrentOffset) + "'",
  67         std::make_error_code(std::errc::invalid_argument));
  68   CurrentOffset = Offset;
  69   H.Thread = Extractor.getU64(&Offset);
  70   if (Offset == CurrentOffset)
  71     return make_error<StringError>(
  72         Twine("Error parsing block header thread id at offset '") +
  73             Twine(CurrentOffset) + "'",
  74         std::make_error_code(std::errc::invalid_argument));
  75   return H;
  76 }
  77
  78 static Expected<std::vector<Profile::FuncID>> readPath(DataExtractor &Extractor,
  79                                                        uint32_t &Offset) {
  80   // We're reading a sequence of int32_t's until we find a 0.
  81   std::vector<Profile::FuncID> Path;
  82   auto CurrentOffset = Offset;
  83   int32_t FuncId;
  84   do {
  85     FuncId = Extractor.getSigned(&Offset, 4);
  86     if (CurrentOffset == Offset)
  87       return make_error<StringError>(
  88           Twine("Error parsing path at offset '") + Twine(CurrentOffset) + "'",
  89           std::make_error_code(std::errc::invalid_argument));
  90     CurrentOffset = Offset;
  91     Path.push_back(FuncId);
  92   } while (FuncId != 0);
  93   return std::move(Path);
  94 }
  95
  96 static Expected<Profile::Data> readData(DataExtractor &Extractor,
  97                                         uint32_t &Offset) {
  98   // We expect a certain number of elements for Data:
  99   //   - A 64-bit CallCount
 100   //   - A 64-bit CumulativeLocalTime counter
 101   Profile::Data D;
 102   auto CurrentOffset = Offset;
 103   D.CallCount = Extractor.getU64(&Offset);
 104   if (CurrentOffset == Offset)
 105     return make_error<StringError>(
 106         Twine("Error parsing call counts at offset '") + Twine(CurrentOffset) +
 107             "'",
 108         std::make_error_code(std::errc::invalid_argument));
 109   CurrentOffset = Offset;
 110   D.CumulativeLocalTime = Extractor.getU64(&Offset);
 111   if (CurrentOffset == Offset)
 112     return make_error<StringError>(
 113         Twine("Error parsing cumulative local time at offset '") +
 114             Twine(CurrentOffset) + "'",
 115         std::make_error_code(std::errc::invalid_argument));
 116   return D;
 117 }
 118
 119 } // namespace
 120
 121 Error Profile::addBlock(Block &&B) {
 122   if (B.PathData.empty())
 123     return make_error<StringError>(
 124         "Block may not have empty path data.",
 125         std::make_error_code(std::errc::invalid_argument));
 126
 127   Blocks.emplace_back(std::move(B));
 128   return Error::success();
 129 }
 130
 131 Expected<std::vector<Profile::FuncID>> Profile::expandPath(PathID P) const {
 132   auto It = PathIDMap.find(P);
 133   if (It == PathIDMap.end())
 134     return make_error<StringError>(
 135         Twine("PathID not found: ") + Twine(P),
 136         std::make_error_code(std::errc::invalid_argument));
 137   std::vector<Profile::FuncID> Path;
 138   for (auto Node = It->second; Node; Node = Node->Caller)
 139     Path.push_back(Node->Func);
 140   return std::move(Path);
 141 }
 142
 143 Profile::PathID Profile::internPath(ArrayRef<FuncID> P) {
 144   if (P.empty())
 145     return 0;
 146
 147   auto RootToLeafPath = reverse(P);
 148
 149   // Find the root.
 150   auto It = RootToLeafPath.begin();
 151   auto PathRoot = *It++;
 152   auto RootIt =
 153       find_if(Roots, [PathRoot](TrieNode *N) { return N->Func == PathRoot; });
 154
 155   // If we've not seen this root before, remember it.
 156   TrieNode *Node = nullptr;
 157   if (RootIt == Roots.end()) {
 158     NodeStorage.emplace_back();
 159     Node = &NodeStorage.back();
 160     Node->Func = PathRoot;
 161     Roots.push_back(Node);
 162   } else {
 163     Node = *RootIt;
 164   }
 165
 166   // Now traverse the path, re-creating if necessary.
 167   while (It != RootToLeafPath.end()) {
 168     auto NodeFuncID = *It++;
 169     auto CalleeIt = find_if(Node->Callees, [NodeFuncID](TrieNode *N) {
 170       return N->Func == NodeFuncID;
 171     });
 172     if (CalleeIt == Node->Callees.end()) {
 173       NodeStorage.emplace_back();
 174       auto NewNode = &NodeStorage.back();
 175       NewNode->Func = NodeFuncID;
 176       NewNode->Caller = Node;
 177       Node->Callees.push_back(NewNode);
 178       Node = NewNode;
 179     } else {
 180       Node = *CalleeIt;
 181     }
 182   }
 183
 184   // At this point, Node *must* be pointing at the leaf.
 185   assert(Node->Func == P.front());
 186   if (Node->ID == 0) {
 187     Node->ID = NextID++;
 188     PathIDMap.insert({Node->ID, Node});
 189   }
 190   return Node->ID;
 191 }
 192
 193 Profile mergeProfilesByThread(const Profile &L, const Profile &R) {
 194   Profile Merged;
 195   using PathDataMap = DenseMap<Profile::PathID, Profile::Data>;
 196   using PathDataMapPtr = std::unique_ptr<PathDataMap>;
 197   using PathDataVector = decltype(Profile::Block::PathData);
 198   using ThreadProfileIndexMap = DenseMap<Profile::ThreadID, PathDataMapPtr>;
 199   ThreadProfileIndexMap ThreadProfileIndex;
 200
 201   for (const auto &P : {std::ref(L), std::ref(R)})
 202     for (const auto &Block : P.get()) {
 203       ThreadProfileIndexMap::iterator It;
 204       std::tie(It, std::ignore) = ThreadProfileIndex.insert(
 205           {Block.Thread, PathDataMapPtr{new PathDataMap()}});
 206       for (const auto &PathAndData : Block.PathData) {
 207         auto &PathID = PathAndData.first;
 208         auto &Data = PathAndData.second;
 209         auto NewPathID =
 210             Merged.internPath(cantFail(P.get().expandPath(PathID)));
 211         PathDataMap::iterator PathDataIt;
 212         bool Inserted;
 213         std::tie(PathDataIt, Inserted) = It->second->insert({NewPathID, Data});
 214         if (!Inserted) {
 215           auto &ExistingData = PathDataIt->second;
 216           ExistingData.CallCount += Data.CallCount;
 217           ExistingData.CumulativeLocalTime += Data.CumulativeLocalTime;
 218         }
 219       }
 220     }
 221
 222   for (const auto &IndexedThreadBlock : ThreadProfileIndex) {
 223     PathDataVector PathAndData;
 224     PathAndData.reserve(IndexedThreadBlock.second->size());
 225     copy(*IndexedThreadBlock.second, std::back_inserter(PathAndData));
 226     cantFail(
 227         Merged.addBlock({IndexedThreadBlock.first, std::move(PathAndData)}));
 228   }
 229   return Merged;
 230 }
 231
 232 Profile mergeProfilesByStack(const Profile &L, const Profile &R) {
 233   Profile Merged;
 234   using PathDataMap = DenseMap<Profile::PathID, Profile::Data>;
 235   PathDataMap PathData;
 236   using PathDataVector = decltype(Profile::Block::PathData);
 237   for (const auto &P : {std::ref(L), std::ref(R)})
 238     for (const auto &Block : P.get())
 239       for (const auto &PathAndData : Block.PathData) {
 240         auto &PathId = PathAndData.first;
 241         auto &Data = PathAndData.second;
 242         auto NewPathID =
 243             Merged.internPath(cantFail(P.get().expandPath(PathId)));
 244         PathDataMap::iterator PathDataIt;
 245         bool Inserted;
 246         std::tie(PathDataIt, Inserted) = PathData.insert({NewPathID, Data});
 247         if (!Inserted) {
 248           auto &ExistingData = PathDataIt->second;
 249           ExistingData.CallCount += Data.CallCount;
 250           ExistingData.CumulativeLocalTime += Data.CumulativeLocalTime;
 251         }
 252       }
 253
 254   // In the end there's a single Block, for thread 0.
 255   PathDataVector Block;
 256   Block.reserve(PathData.size());
 257   copy(PathData, std::back_inserter(Block));
 258   cantFail(Merged.addBlock({0, std::move(Block)}));
 259   return Merged;
 260 }
 261
 262 Expected<Profile> loadProfile(StringRef Filename) {
 263   int Fd;
 264   if (auto EC = sys::fs::openFileForRead(Filename, Fd))
 265     return make_error<StringError>(
 266         Twine("Cannot read profile from '") + Filename + "'", EC);
 267
 268   uint64_t FileSize;
 269   if (auto EC = sys::fs::file_size(Filename, FileSize))
 270     return make_error<StringError>(
 271         Twine("Cannot get filesize of '") + Filename + "'", EC);
 272
 273   std::error_code EC;
 274   sys::fs::mapped_file_region MappedFile(
 275       Fd, sys::fs::mapped_file_region::mapmode::readonly, FileSize, 0, EC);
 276   if (EC)
 277     return make_error<StringError>(
 278         Twine("Cannot mmap profile '") + Filename + "'", EC);
 279   StringRef Data(MappedFile.data(), MappedFile.size());
 280
 281   Profile P;
 282   uint32_t Offset = 0;
 283   DataExtractor Extractor(Data, true, 8);
 284
 285   // For each block we get from the file:
 286   while (Offset != MappedFile.size()) {
 287     auto HeaderOrError = readBlockHeader(Extractor, Offset);
 288     if (!HeaderOrError)
 289       return HeaderOrError.takeError();
 290
 291     // TODO: Maybe store this header information for each block, even just for
 292     // debugging?
 293     const auto &Header = HeaderOrError.get();
 294
 295     // Read in the path data.
 296     auto PathOrError = readPath(Extractor, Offset);
 297     if (!PathOrError)
 298       return PathOrError.takeError();
 299     const auto &Path = PathOrError.get();
 300
 301     // For each path we encounter, we should intern it to get a PathID.
 302     auto DataOrError = readData(Extractor, Offset);
 303     if (!DataOrError)
 304       return DataOrError.takeError();
 305     auto &Data = DataOrError.get();
 306
 307     if (auto E =
 308             P.addBlock(Profile::Block{Profile::ThreadID{Header.Thread},
 309                                       {{P.internPath(Path), std::move(Data)}}}))
 310       return std::move(E);
 311   }
 312
 313   return P;
 314 }
 315
 316 namespace {
 317
 318 struct StackEntry {
 319   uint64_t Timestamp;
 320   Profile::FuncID FuncId;
 321 };
 322
 323 } // namespace
 324
 325 Expected<Profile> profileFromTrace(const Trace &T) {
 326   Profile P;
 327
 328   // The implementation of the algorithm re-creates the execution of
 329   // the functions based on the trace data. To do this, we set up a number of
 330   // data structures to track the execution context of every thread in the
 331   // Trace.
 332   DenseMap<Profile::ThreadID, std::vector<StackEntry>> ThreadStacks;
 333   DenseMap<Profile::ThreadID, DenseMap<Profile::PathID, Profile::Data>>
 334       ThreadPathData;
 335
 336   //  We then do a pass through the Trace to account data on a per-thread-basis.
 337   for (const auto &E : T) {
 338     auto &TSD = ThreadStacks[E.TId];
 339     switch (E.Type) {
 340     case RecordTypes::ENTER:
 341     case RecordTypes::ENTER_ARG:
 342
 343       // Push entries into the function call stack.
 344       TSD.push_back({E.TSC, E.FuncId});
 345       break;
 346
 347     case RecordTypes::EXIT:
 348     case RecordTypes::TAIL_EXIT:
 349
 350       // Exits cause some accounting to happen, based on the state of the stack.
 351       // For each function we pop off the stack, we take note of the path and
 352       // record the cumulative state for this path. As we're doing this, we
 353       // intern the path into the Profile.
 354       while (!TSD.empty()) {
 355         auto Top = TSD.back();
 356         auto FunctionLocalTime = AbsoluteDifference(Top.Timestamp, E.TSC);
 357         SmallVector<Profile::FuncID, 16> Path;
 358         transform(reverse(TSD), std::back_inserter(Path),
 359                   std::mem_fn(&StackEntry::FuncId));
 360         auto InternedPath = P.internPath(Path);
 361         auto &TPD = ThreadPathData[E.TId][InternedPath];
 362         ++TPD.CallCount;
 363         TPD.CumulativeLocalTime += FunctionLocalTime;
 364         TSD.pop_back();
 365
 366         // If we've matched the corresponding entry event for this function,
 367         // then we exit the loop.
 368         if (Top.FuncId == E.FuncId)
 369           break;
 370
 371         // FIXME: Consider the intermediate times and the cumulative tree time
 372         // as well.
 373       }
 374
 375       break;
 376
 377     case RecordTypes::CUSTOM_EVENT:
 378     case RecordTypes::TYPED_EVENT:
 379       // TODO: Support an extension point to allow handling of custom and typed
 380       // events in profiles.
 381       break;
 382     }
 383   }
 384
 385   // Once we've gone through the Trace, we now create one Block per thread in
 386   // the Profile.
 387   for (const auto &ThreadPaths : ThreadPathData) {
 388     const auto &TID = ThreadPaths.first;
 389     const auto &PathsData = ThreadPaths.second;
 390     if (auto E = P.addBlock({
 391             TID,
 392             std::vector<std::pair<Profile::PathID, Profile::Data>>(
 393                 PathsData.begin(), PathsData.end()),
 394         }))
 395       return std::move(E);
 396   }
 397
 398   return P;
 399 }
 400
 401 } // namespace xray
 402 } // namespace llvm