1 files changed, 292 insertions, 0 deletions
diff --git a/llvm/lib/Support/CachePruning.cpp b/llvm/lib/Support/CachePruning.cpp
new file mode 100644
index 000000000000..7a2f6c53435a
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+++ b/llvm/lib/Support/CachePruning.cpp
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+//===-CachePruning.cpp - LLVM Cache Directory Pruning ---------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the pruning of a directory based on least recently used.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/CachePruning.h"
+
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
+
+#define DEBUG_TYPE "cache-pruning"
+
+#include <set>
+#include <system_error>
+
+using namespace llvm;
+
+namespace {
+struct FileInfo {
+  sys::TimePoint<> Time;
+  uint64_t Size;
+  std::string Path;
+
+  /// Used to determine which files to prune first. Also used to determine
+  /// set membership, so must take into account all fields.
+  bool operator<(const FileInfo &Other) const {
+    return std::tie(Time, Other.Size, Path) <
+           std::tie(Other.Time, Size, Other.Path);
+  }
+};
+} // anonymous namespace
+
+/// Write a new timestamp file with the given path. This is used for the pruning
+/// interval option.
+static void writeTimestampFile(StringRef TimestampFile) {
+  std::error_code EC;
+  raw_fd_ostream Out(TimestampFile.str(), EC, sys::fs::OF_None);
+}
+
+static Expected<std::chrono::seconds> parseDuration(StringRef Duration) {
+  if (Duration.empty())
+    return make_error<StringError>("Duration must not be empty",
+                                   inconvertibleErrorCode());
+
+  StringRef NumStr = Duration.slice(0, Duration.size()-1);
+  uint64_t Num;
+  if (NumStr.getAsInteger(0, Num))
+    return make_error<StringError>("'" + NumStr + "' not an integer",
+                                   inconvertibleErrorCode());
+
+  switch (Duration.back()) {
+  case 's':
+    return std::chrono::seconds(Num);
+  case 'm':
+    return std::chrono::minutes(Num);
+  case 'h':
+    return std::chrono::hours(Num);
+  default:
+    return make_error<StringError>("'" + Duration +
+                                       "' must end with one of 's', 'm' or 'h'",
+                                   inconvertibleErrorCode());
+  }
+}
+
+Expected<CachePruningPolicy>
+llvm::parseCachePruningPolicy(StringRef PolicyStr) {
+  CachePruningPolicy Policy;
+  std::pair<StringRef, StringRef> P = {"", PolicyStr};
+  while (!P.second.empty()) {
+    P = P.second.split(':');
+
+    StringRef Key, Value;
+    std::tie(Key, Value) = P.first.split('=');
+    if (Key == "prune_interval") {
+      auto DurationOrErr = parseDuration(Value);
+      if (!DurationOrErr)
+        return DurationOrErr.takeError();
+      Policy.Interval = *DurationOrErr;
+    } else if (Key == "prune_after") {
+      auto DurationOrErr = parseDuration(Value);
+      if (!DurationOrErr)
+        return DurationOrErr.takeError();
+      Policy.Expiration = *DurationOrErr;
+    } else if (Key == "cache_size") {
+      if (Value.back() != '%')
+        return make_error<StringError>("'" + Value + "' must be a percentage",
+                                       inconvertibleErrorCode());
+      StringRef SizeStr = Value.drop_back();
+      uint64_t Size;
+      if (SizeStr.getAsInteger(0, Size))
+        return make_error<StringError>("'" + SizeStr + "' not an integer",
+                                       inconvertibleErrorCode());
+      if (Size > 100)
+        return make_error<StringError>("'" + SizeStr +
+                                           "' must be between 0 and 100",
+                                       inconvertibleErrorCode());
+      Policy.MaxSizePercentageOfAvailableSpace = Size;
+    } else if (Key == "cache_size_bytes") {
+      uint64_t Mult = 1;
+      switch (tolower(Value.back())) {
+      case 'k':
+        Mult = 1024;
+        Value = Value.drop_back();
+        break;
+      case 'm':
+        Mult = 1024 * 1024;
+        Value = Value.drop_back();
+        break;
+      case 'g':
+        Mult = 1024 * 1024 * 1024;
+        Value = Value.drop_back();
+        break;
+      }
+      uint64_t Size;
+      if (Value.getAsInteger(0, Size))
+        return make_error<StringError>("'" + Value + "' not an integer",
+                                       inconvertibleErrorCode());
+      Policy.MaxSizeBytes = Size * Mult;
+    } else if (Key == "cache_size_files") {
+      if (Value.getAsInteger(0, Policy.MaxSizeFiles))
+        return make_error<StringError>("'" + Value + "' not an integer",
+                                       inconvertibleErrorCode());
+    } else {
+      return make_error<StringError>("Unknown key: '" + Key + "'",
+                                     inconvertibleErrorCode());
+    }
+  }
+
+  return Policy;
+}
+
+/// Prune the cache of files that haven't been accessed in a long time.
+bool llvm::pruneCache(StringRef Path, CachePruningPolicy Policy) {
+  using namespace std::chrono;
+
+  if (Path.empty())
+    return false;
+
+  bool isPathDir;
+  if (sys::fs::is_directory(Path, isPathDir))
+    return false;
+
+  if (!isPathDir)
+    return false;
+
+  Policy.MaxSizePercentageOfAvailableSpace =
+      std::min(Policy.MaxSizePercentageOfAvailableSpace, 100u);
+
+  if (Policy.Expiration == seconds(0) &&
+      Policy.MaxSizePercentageOfAvailableSpace == 0 &&
+      Policy.MaxSizeBytes == 0 && Policy.MaxSizeFiles == 0) {
+    LLVM_DEBUG(dbgs() << "No pruning settings set, exit early\n");
+    // Nothing will be pruned, early exit
+    return false;
+  }
+
+  // Try to stat() the timestamp file.
+  SmallString<128> TimestampFile(Path);
+  sys::path::append(TimestampFile, "llvmcache.timestamp");
+  sys::fs::file_status FileStatus;
+  const auto CurrentTime = system_clock::now();
+  if (auto EC = sys::fs::status(TimestampFile, FileStatus)) {
+    if (EC == errc::no_such_file_or_directory) {
+      // If the timestamp file wasn't there, create one now.
+      writeTimestampFile(TimestampFile);
+    } else {
+      // Unknown error?
+      return false;
+    }
+  } else {
+    if (!Policy.Interval)
+      return false;
+    if (Policy.Interval != seconds(0)) {
+      // Check whether the time stamp is older than our pruning interval.
+      // If not, do nothing.
+      const auto TimeStampModTime = FileStatus.getLastModificationTime();
+      auto TimeStampAge = CurrentTime - TimeStampModTime;
+      if (TimeStampAge <= *Policy.Interval) {
+        LLVM_DEBUG(dbgs() << "Timestamp file too recent ("
+                          << duration_cast<seconds>(TimeStampAge).count()
+                          << "s old), do not prune.\n");
+        return false;
+      }
+    }
+    // Write a new timestamp file so that nobody else attempts to prune.
+    // There is a benign race condition here, if two processes happen to
+    // notice at the same time that the timestamp is out-of-date.
+    writeTimestampFile(TimestampFile);
+  }
+
+  // Keep track of files to delete to get below the size limit.
+  // Order by time of last use so that recently used files are preserved.
+  std::set<FileInfo> FileInfos;
+  uint64_t TotalSize = 0;
+
+  // Walk the entire directory cache, looking for unused files.
+  std::error_code EC;
+  SmallString<128> CachePathNative;
+  sys::path::native(Path, CachePathNative);
+  // Walk all of the files within this directory.
+  for (sys::fs::directory_iterator File(CachePathNative, EC), FileEnd;
+       File != FileEnd && !EC; File.increment(EC)) {
+    // Ignore any files not beginning with the string "llvmcache-". This
+    // includes the timestamp file as well as any files created by the user.
+    // This acts as a safeguard against data loss if the user specifies the
+    // wrong directory as their cache directory.
+    if (!sys::path::filename(File->path()).startswith("llvmcache-"))
+      continue;
+
+    // Look at this file. If we can't stat it, there's nothing interesting
+    // there.
+    ErrorOr<sys::fs::basic_file_status> StatusOrErr = File->status();
+    if (!StatusOrErr) {
+      LLVM_DEBUG(dbgs() << "Ignore " << File->path() << " (can't stat)\n");
+      continue;
+    }
+
+    // If the file hasn't been used recently enough, delete it
+    const auto FileAccessTime = StatusOrErr->getLastAccessedTime();
+    auto FileAge = CurrentTime - FileAccessTime;
+    if (Policy.Expiration != seconds(0) && FileAge > Policy.Expiration) {
+      LLVM_DEBUG(dbgs() << "Remove " << File->path() << " ("
+                        << duration_cast<seconds>(FileAge).count()
+                        << "s old)\n");
+      sys::fs::remove(File->path());
+      continue;
+    }
+
+    // Leave it here for now, but add it to the list of size-based pruning.
+    TotalSize += StatusOrErr->getSize();
+    FileInfos.insert({FileAccessTime, StatusOrErr->getSize(), File->path()});
+  }
+
+  auto FileInfo = FileInfos.begin();
+  size_t NumFiles = FileInfos.size();
+
+  auto RemoveCacheFile = [&]() {
+    // Remove the file.
+    sys::fs::remove(FileInfo->Path);
+    // Update size
+    TotalSize -= FileInfo->Size;
+    NumFiles--;
+    LLVM_DEBUG(dbgs() << " - Remove " << FileInfo->Path << " (size "
+                      << FileInfo->Size << "), new occupancy is " << TotalSize
+                      << "%\n");
+    ++FileInfo;
+  };
+
+  // Prune for number of files.
+  if (Policy.MaxSizeFiles)
+    while (NumFiles > Policy.MaxSizeFiles)
+      RemoveCacheFile();
+
+  // Prune for size now if needed
+  if (Policy.MaxSizePercentageOfAvailableSpace > 0 || Policy.MaxSizeBytes > 0) {
+    auto ErrOrSpaceInfo = sys::fs::disk_space(Path);
+    if (!ErrOrSpaceInfo) {
+      report_fatal_error("Can't get available size");
+    }
+    sys::fs::space_info SpaceInfo = ErrOrSpaceInfo.get();
+    auto AvailableSpace = TotalSize + SpaceInfo.free;
+
+    if (Policy.MaxSizePercentageOfAvailableSpace == 0)
+      Policy.MaxSizePercentageOfAvailableSpace = 100;
+    if (Policy.MaxSizeBytes == 0)
+      Policy.MaxSizeBytes = AvailableSpace;
+    auto TotalSizeTarget = std::min<uint64_t>(
+        AvailableSpace * Policy.MaxSizePercentageOfAvailableSpace / 100ull,
+        Policy.MaxSizeBytes);
+
+    LLVM_DEBUG(dbgs() << "Occupancy: " << ((100 * TotalSize) / AvailableSpace)
+                      << "% target is: "
+                      << Policy.MaxSizePercentageOfAvailableSpace << "%, "
+                      << Policy.MaxSizeBytes << " bytes\n");
+
+    // Remove the oldest accessed files first, till we get below the threshold.
+    while (TotalSize > TotalSizeTarget && FileInfo != FileInfos.end())
+      RemoveCacheFile();
+  }
+  return true;
+}