1 //===-CachePruning.cpp - LLVM Cache Directory Pruning ---------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the pruning of a directory based on least recently used.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Support/CachePruning.h"
16 #include "llvm/Support/Debug.h"
17 #include "llvm/Support/Errc.h"
18 #include "llvm/Support/Error.h"
19 #include "llvm/Support/FileSystem.h"
20 #include "llvm/Support/Path.h"
21 #include "llvm/Support/raw_ostream.h"
23 #define DEBUG_TYPE "cache-pruning"
26 #include <system_error>
30 /// Write a new timestamp file with the given path. This is used for the pruning
32 static void writeTimestampFile(StringRef TimestampFile) {
34 raw_fd_ostream Out(TimestampFile.str(), EC, sys::fs::F_None);
37 static Expected<std::chrono::seconds> parseDuration(StringRef Duration) {
39 return make_error<StringError>("Duration must not be empty",
40 inconvertibleErrorCode());
42 StringRef NumStr = Duration.slice(0, Duration.size()-1);
44 if (NumStr.getAsInteger(0, Num))
45 return make_error<StringError>("'" + NumStr + "' not an integer",
46 inconvertibleErrorCode());
48 switch (Duration.back()) {
50 return std::chrono::seconds(Num);
52 return std::chrono::minutes(Num);
54 return std::chrono::hours(Num);
56 return make_error<StringError>("'" + Duration +
57 "' must end with one of 's', 'm' or 'h'",
58 inconvertibleErrorCode());
62 Expected<CachePruningPolicy>
63 llvm::parseCachePruningPolicy(StringRef PolicyStr) {
64 CachePruningPolicy Policy;
65 std::pair<StringRef, StringRef> P = {"", PolicyStr};
66 while (!P.second.empty()) {
67 P = P.second.split(':');
70 std::tie(Key, Value) = P.first.split('=');
71 if (Key == "prune_interval") {
72 auto DurationOrErr = parseDuration(Value);
74 return DurationOrErr.takeError();
75 Policy.Interval = *DurationOrErr;
76 } else if (Key == "prune_after") {
77 auto DurationOrErr = parseDuration(Value);
79 return DurationOrErr.takeError();
80 Policy.Expiration = *DurationOrErr;
81 } else if (Key == "cache_size") {
82 if (Value.back() != '%')
83 return make_error<StringError>("'" + Value + "' must be a percentage",
84 inconvertibleErrorCode());
85 StringRef SizeStr = Value.slice(0, Value.size() - 1);
87 if (SizeStr.getAsInteger(0, Size))
88 return make_error<StringError>("'" + SizeStr + "' not an integer",
89 inconvertibleErrorCode());
91 return make_error<StringError>("'" + SizeStr +
92 "' must be between 0 and 100",
93 inconvertibleErrorCode());
94 Policy.PercentageOfAvailableSpace = Size;
96 return make_error<StringError>("Unknown key: '" + Key + "'",
97 inconvertibleErrorCode());
104 /// Prune the cache of files that haven't been accessed in a long time.
105 bool llvm::pruneCache(StringRef Path, CachePruningPolicy Policy) {
106 using namespace std::chrono;
112 if (sys::fs::is_directory(Path, isPathDir))
118 Policy.PercentageOfAvailableSpace =
119 std::min(Policy.PercentageOfAvailableSpace, 100u);
121 if (Policy.Expiration == seconds(0) &&
122 Policy.PercentageOfAvailableSpace == 0) {
123 DEBUG(dbgs() << "No pruning settings set, exit early\n");
124 // Nothing will be pruned, early exit
128 // Try to stat() the timestamp file.
129 SmallString<128> TimestampFile(Path);
130 sys::path::append(TimestampFile, "llvmcache.timestamp");
131 sys::fs::file_status FileStatus;
132 const auto CurrentTime = system_clock::now();
133 if (auto EC = sys::fs::status(TimestampFile, FileStatus)) {
134 if (EC == errc::no_such_file_or_directory) {
135 // If the timestamp file wasn't there, create one now.
136 writeTimestampFile(TimestampFile);
142 if (Policy.Interval == seconds(0)) {
143 // Check whether the time stamp is older than our pruning interval.
144 // If not, do nothing.
145 const auto TimeStampModTime = FileStatus.getLastModificationTime();
146 auto TimeStampAge = CurrentTime - TimeStampModTime;
147 if (TimeStampAge <= Policy.Interval) {
148 DEBUG(dbgs() << "Timestamp file too recent ("
149 << duration_cast<seconds>(TimeStampAge).count()
150 << "s old), do not prune.\n");
154 // Write a new timestamp file so that nobody else attempts to prune.
155 // There is a benign race condition here, if two processes happen to
156 // notice at the same time that the timestamp is out-of-date.
157 writeTimestampFile(TimestampFile);
160 bool ShouldComputeSize = (Policy.PercentageOfAvailableSpace > 0);
162 // Keep track of space
163 std::set<std::pair<uint64_t, std::string>> FileSizes;
164 uint64_t TotalSize = 0;
165 // Helper to add a path to the set of files to consider for size-based
166 // pruning, sorted by size.
167 auto AddToFileListForSizePruning =
168 [&](StringRef Path) {
169 if (!ShouldComputeSize)
171 TotalSize += FileStatus.getSize();
173 std::make_pair(FileStatus.getSize(), std::string(Path)));
176 // Walk the entire directory cache, looking for unused files.
178 SmallString<128> CachePathNative;
179 sys::path::native(Path, CachePathNative);
180 // Walk all of the files within this directory.
181 for (sys::fs::directory_iterator File(CachePathNative, EC), FileEnd;
182 File != FileEnd && !EC; File.increment(EC)) {
183 // Ignore any files not beginning with the string "llvmcache-". This
184 // includes the timestamp file as well as any files created by the user.
185 // This acts as a safeguard against data loss if the user specifies the
186 // wrong directory as their cache directory.
187 if (!sys::path::filename(File->path()).startswith("llvmcache-"))
190 // Look at this file. If we can't stat it, there's nothing interesting
192 if (sys::fs::status(File->path(), FileStatus)) {
193 DEBUG(dbgs() << "Ignore " << File->path() << " (can't stat)\n");
197 // If the file hasn't been used recently enough, delete it
198 const auto FileAccessTime = FileStatus.getLastAccessedTime();
199 auto FileAge = CurrentTime - FileAccessTime;
200 if (FileAge > Policy.Expiration) {
201 DEBUG(dbgs() << "Remove " << File->path() << " ("
202 << duration_cast<seconds>(FileAge).count() << "s old)\n");
203 sys::fs::remove(File->path());
207 // Leave it here for now, but add it to the list of size-based pruning.
208 AddToFileListForSizePruning(File->path());
211 // Prune for size now if needed
212 if (ShouldComputeSize) {
213 auto ErrOrSpaceInfo = sys::fs::disk_space(Path);
214 if (!ErrOrSpaceInfo) {
215 report_fatal_error("Can't get available size");
217 sys::fs::space_info SpaceInfo = ErrOrSpaceInfo.get();
218 auto AvailableSpace = TotalSize + SpaceInfo.free;
219 auto FileAndSize = FileSizes.rbegin();
220 DEBUG(dbgs() << "Occupancy: " << ((100 * TotalSize) / AvailableSpace)
221 << "% target is: " << Policy.PercentageOfAvailableSpace
223 // Remove the oldest accessed files first, till we get below the threshold
224 while (((100 * TotalSize) / AvailableSpace) >
225 Policy.PercentageOfAvailableSpace &&
226 FileAndSize != FileSizes.rend()) {
228 sys::fs::remove(FileAndSize->second);
230 TotalSize -= FileAndSize->first;
231 DEBUG(dbgs() << " - Remove " << FileAndSize->second << " (size "
232 << FileAndSize->first << "), new occupancy is " << TotalSize