llvm/lib/Support/CachePruning.cpp

   1 //===-CachePruning.cpp - LLVM Cache Directory Pruning ---------------------===//
   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 // This file implements the pruning of a directory based on least recently used.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Support/CachePruning.h"
  14 #include "llvm/ADT/StringRef.h"
  15 #include "llvm/Support/Debug.h"
  16 #include "llvm/Support/Errc.h"
  17 #include "llvm/Support/Error.h"
  18 #include "llvm/Support/FileSystem.h"
  19 #include "llvm/Support/Path.h"
  20 #include "llvm/Support/raw_ostream.h"
  21
  22 #define DEBUG_TYPE "cache-pruning"
  23
  24 #include <set>
  25 #include <system_error>
  26
  27 using namespace llvm;
  28
  29 namespace {
  30 struct FileInfo {
  31   sys::TimePoint<> Time;
  32   uint64_t Size;
  33   std::string Path;
  34
  35   /// Used to determine which files to prune first. Also used to determine
  36   /// set membership, so must take into account all fields.
  37   bool operator<(const FileInfo &Other) const {
  38     return std::tie(Time, Other.Size, Path) <
  39            std::tie(Other.Time, Size, Other.Path);
  40   }
  41 };
  42 } // anonymous namespace
  43
  44 /// Write a new timestamp file with the given path. This is used for the pruning
  45 /// interval option.
  46 static void writeTimestampFile(StringRef TimestampFile) {
  47   std::error_code EC;
  48   raw_fd_ostream Out(TimestampFile.str(), EC, sys::fs::OF_None);
  49 }
  50
  51 static Expected<std::chrono::seconds> parseDuration(StringRef Duration) {
  52   if (Duration.empty())
  53     return make_error<StringError>("Duration must not be empty",
  54                                    inconvertibleErrorCode());
  55
  56   StringRef NumStr = Duration.slice(0, Duration.size()-1);
  57   uint64_t Num;
  58   if (NumStr.getAsInteger(0, Num))
  59     return make_error<StringError>("'" + NumStr + "' not an integer",
  60                                    inconvertibleErrorCode());
  61
  62   switch (Duration.back()) {
  63   case 's':
  64     return std::chrono::seconds(Num);
  65   case 'm':
  66     return std::chrono::minutes(Num);
  67   case 'h':
  68     return std::chrono::hours(Num);
  69   default:
  70     return make_error<StringError>("'" + Duration +
  71                                        "' must end with one of 's', 'm' or 'h'",
  72                                    inconvertibleErrorCode());
  73   }
  74 }
  75
  76 Expected<CachePruningPolicy>
  77 llvm::parseCachePruningPolicy(StringRef PolicyStr) {
  78   CachePruningPolicy Policy;
  79   std::pair<StringRef, StringRef> P = {"", PolicyStr};
  80   while (!P.second.empty()) {
  81     P = P.second.split(':');
  82
  83     StringRef Key, Value;
  84     std::tie(Key, Value) = P.first.split('=');
  85     if (Key == "prune_interval") {
  86       auto DurationOrErr = parseDuration(Value);
  87       if (!DurationOrErr)
  88         return DurationOrErr.takeError();
  89       Policy.Interval = *DurationOrErr;
  90     } else if (Key == "prune_after") {
  91       auto DurationOrErr = parseDuration(Value);
  92       if (!DurationOrErr)
  93         return DurationOrErr.takeError();
  94       Policy.Expiration = *DurationOrErr;
  95     } else if (Key == "cache_size") {
  96       if (Value.back() != '%')
  97         return make_error<StringError>("'" + Value + "' must be a percentage",
  98                                        inconvertibleErrorCode());
  99       StringRef SizeStr = Value.drop_back();
 100       uint64_t Size;
 101       if (SizeStr.getAsInteger(0, Size))
 102         return make_error<StringError>("'" + SizeStr + "' not an integer",
 103                                        inconvertibleErrorCode());
 104       if (Size > 100)
 105         return make_error<StringError>("'" + SizeStr +
 106                                            "' must be between 0 and 100",
 107                                        inconvertibleErrorCode());
 108       Policy.MaxSizePercentageOfAvailableSpace = Size;
 109     } else if (Key == "cache_size_bytes") {
 110       uint64_t Mult = 1;
 111       switch (tolower(Value.back())) {
 112       case 'k':
 113         Mult = 1024;
 114         Value = Value.drop_back();
 115         break;
 116       case 'm':
 117         Mult = 1024 * 1024;
 118         Value = Value.drop_back();
 119         break;
 120       case 'g':
 121         Mult = 1024 * 1024 * 1024;
 122         Value = Value.drop_back();
 123         break;
 124       }
 125       uint64_t Size;
 126       if (Value.getAsInteger(0, Size))
 127         return make_error<StringError>("'" + Value + "' not an integer",
 128                                        inconvertibleErrorCode());
 129       Policy.MaxSizeBytes = Size * Mult;
 130     } else if (Key == "cache_size_files") {
 131       if (Value.getAsInteger(0, Policy.MaxSizeFiles))
 132         return make_error<StringError>("'" + Value + "' not an integer",
 133                                        inconvertibleErrorCode());
 134     } else {
 135       return make_error<StringError>("Unknown key: '" + Key + "'",
 136                                      inconvertibleErrorCode());
 137     }
 138   }
 139
 140   return Policy;
 141 }
 142
 143 /// Prune the cache of files that haven't been accessed in a long time.
 144 bool llvm::pruneCache(StringRef Path, CachePruningPolicy Policy) {
 145   using namespace std::chrono;
 146
 147   if (Path.empty())
 148     return false;
 149
 150   bool isPathDir;
 151   if (sys::fs::is_directory(Path, isPathDir))
 152     return false;
 153
 154   if (!isPathDir)
 155     return false;
 156
 157   Policy.MaxSizePercentageOfAvailableSpace =
 158       std::min(Policy.MaxSizePercentageOfAvailableSpace, 100u);
 159
 160   if (Policy.Expiration == seconds(0) &&
 161       Policy.MaxSizePercentageOfAvailableSpace == 0 &&
 162       Policy.MaxSizeBytes == 0 && Policy.MaxSizeFiles == 0) {
 163     LLVM_DEBUG(dbgs() << "No pruning settings set, exit early\n");
 164     // Nothing will be pruned, early exit
 165     return false;
 166   }
 167
 168   // Try to stat() the timestamp file.
 169   SmallString<128> TimestampFile(Path);
 170   sys::path::append(TimestampFile, "llvmcache.timestamp");
 171   sys::fs::file_status FileStatus;
 172   const auto CurrentTime = system_clock::now();
 173   if (auto EC = sys::fs::status(TimestampFile, FileStatus)) {
 174     if (EC == errc::no_such_file_or_directory) {
 175       // If the timestamp file wasn't there, create one now.
 176       writeTimestampFile(TimestampFile);
 177     } else {
 178       // Unknown error?
 179       return false;
 180     }
 181   } else {
 182     if (!Policy.Interval)
 183       return false;
 184     if (Policy.Interval != seconds(0)) {
 185       // Check whether the time stamp is older than our pruning interval.
 186       // If not, do nothing.
 187       const auto TimeStampModTime = FileStatus.getLastModificationTime();
 188       auto TimeStampAge = CurrentTime - TimeStampModTime;
 189       if (TimeStampAge <= *Policy.Interval) {
 190         LLVM_DEBUG(dbgs() << "Timestamp file too recent ("
 191                           << duration_cast<seconds>(TimeStampAge).count()
 192                           << "s old), do not prune.\n");
 193         return false;
 194       }
 195     }
 196     // Write a new timestamp file so that nobody else attempts to prune.
 197     // There is a benign race condition here, if two processes happen to
 198     // notice at the same time that the timestamp is out-of-date.
 199     writeTimestampFile(TimestampFile);
 200   }
 201
 202   // Keep track of files to delete to get below the size limit.
 203   // Order by time of last use so that recently used files are preserved.
 204   std::set<FileInfo> FileInfos;
 205   uint64_t TotalSize = 0;
 206
 207   // Walk the entire directory cache, looking for unused files.
 208   std::error_code EC;
 209   SmallString<128> CachePathNative;
 210   sys::path::native(Path, CachePathNative);
 211   // Walk all of the files within this directory.
 212   for (sys::fs::directory_iterator File(CachePathNative, EC), FileEnd;
 213        File != FileEnd && !EC; File.increment(EC)) {
 214     // Ignore filenames not beginning with "llvmcache-" or "Thin-". This
 215     // includes the timestamp file as well as any files created by the user.
 216     // This acts as a safeguard against data loss if the user specifies the
 217     // wrong directory as their cache directory.
 218     StringRef filename = sys::path::filename(File->path());
 219     if (!filename.startswith("llvmcache-") && !filename.startswith("Thin-"))
 220       continue;
 221
 222     // Look at this file. If we can't stat it, there's nothing interesting
 223     // there.
 224     ErrorOr<sys::fs::basic_file_status> StatusOrErr = File->status();
 225     if (!StatusOrErr) {
 226       LLVM_DEBUG(dbgs() << "Ignore " << File->path() << " (can't stat)\n");
 227       continue;
 228     }
 229
 230     // If the file hasn't been used recently enough, delete it
 231     const auto FileAccessTime = StatusOrErr->getLastAccessedTime();
 232     auto FileAge = CurrentTime - FileAccessTime;
 233     if (Policy.Expiration != seconds(0) && FileAge > Policy.Expiration) {
 234       LLVM_DEBUG(dbgs() << "Remove " << File->path() << " ("
 235                         << duration_cast<seconds>(FileAge).count()
 236                         << "s old)\n");
 237       sys::fs::remove(File->path());
 238       continue;
 239     }
 240
 241     // Leave it here for now, but add it to the list of size-based pruning.
 242     TotalSize += StatusOrErr->getSize();
 243     FileInfos.insert({FileAccessTime, StatusOrErr->getSize(), File->path()});
 244   }
 245
 246   auto FileInfo = FileInfos.begin();
 247   size_t NumFiles = FileInfos.size();
 248
 249   auto RemoveCacheFile = [&]() {
 250     // Remove the file.
 251     sys::fs::remove(FileInfo->Path);
 252     // Update size
 253     TotalSize -= FileInfo->Size;
 254     NumFiles--;
 255     LLVM_DEBUG(dbgs() << " - Remove " << FileInfo->Path << " (size "
 256                       << FileInfo->Size << "), new occupancy is " << TotalSize
 257                       << "%\n");
 258     ++FileInfo;
 259   };
 260
 261   // Prune for number of files.
 262   if (Policy.MaxSizeFiles)
 263     while (NumFiles > Policy.MaxSizeFiles)
 264       RemoveCacheFile();
 265
 266   // Prune for size now if needed
 267   if (Policy.MaxSizePercentageOfAvailableSpace > 0 || Policy.MaxSizeBytes > 0) {
 268     auto ErrOrSpaceInfo = sys::fs::disk_space(Path);
 269     if (!ErrOrSpaceInfo) {
 270       report_fatal_error("Can't get available size");
 271     }
 272     sys::fs::space_info SpaceInfo = ErrOrSpaceInfo.get();
 273     auto AvailableSpace = TotalSize + SpaceInfo.free;
 274
 275     if (Policy.MaxSizePercentageOfAvailableSpace == 0)
 276       Policy.MaxSizePercentageOfAvailableSpace = 100;
 277     if (Policy.MaxSizeBytes == 0)
 278       Policy.MaxSizeBytes = AvailableSpace;
 279     auto TotalSizeTarget = std::min<uint64_t>(
 280         AvailableSpace * Policy.MaxSizePercentageOfAvailableSpace / 100ull,
 281         Policy.MaxSizeBytes);
 282
 283     LLVM_DEBUG(dbgs() << "Occupancy: " << ((100 * TotalSize) / AvailableSpace)
 284                       << "% target is: "
 285                       << Policy.MaxSizePercentageOfAvailableSpace << "%, "
 286                       << Policy.MaxSizeBytes << " bytes\n");
 287
 288     // Remove the oldest accessed files first, till we get below the threshold.
 289     while (TotalSize > TotalSizeTarget && FileInfo != FileInfos.end())
 290       RemoveCacheFile();
 291   }
 292   return true;
 293 }