1 //===-CachePruning.cpp - LLVM Cache Directory Pruning ---------------------===//
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
7 //===----------------------------------------------------------------------===//
9 // This file implements the pruning of a directory based on least recently used.
11 //===----------------------------------------------------------------------===//
13 #include "llvm/Support/CachePruning.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"
22 #define DEBUG_TYPE "cache-pruning"
25 #include <system_error>
31 sys::TimePoint<> Time;
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);
42 } // anonymous namespace
44 /// Write a new timestamp file with the given path. This is used for the pruning
46 static void writeTimestampFile(StringRef TimestampFile) {
48 raw_fd_ostream Out(TimestampFile.str(), EC, sys::fs::F_None);
51 static Expected<std::chrono::seconds> parseDuration(StringRef Duration) {
53 return make_error<StringError>("Duration must not be empty",
54 inconvertibleErrorCode());
56 StringRef NumStr = Duration.slice(0, Duration.size()-1);
58 if (NumStr.getAsInteger(0, Num))
59 return make_error<StringError>("'" + NumStr + "' not an integer",
60 inconvertibleErrorCode());
62 switch (Duration.back()) {
64 return std::chrono::seconds(Num);
66 return std::chrono::minutes(Num);
68 return std::chrono::hours(Num);
70 return make_error<StringError>("'" + Duration +
71 "' must end with one of 's', 'm' or 'h'",
72 inconvertibleErrorCode());
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(':');
84 std::tie(Key, Value) = P.first.split('=');
85 if (Key == "prune_interval") {
86 auto DurationOrErr = parseDuration(Value);
88 return DurationOrErr.takeError();
89 Policy.Interval = *DurationOrErr;
90 } else if (Key == "prune_after") {
91 auto DurationOrErr = parseDuration(Value);
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();
101 if (SizeStr.getAsInteger(0, Size))
102 return make_error<StringError>("'" + SizeStr + "' not an integer",
103 inconvertibleErrorCode());
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") {
111 switch (tolower(Value.back())) {
114 Value = Value.drop_back();
118 Value = Value.drop_back();
121 Mult = 1024 * 1024 * 1024;
122 Value = Value.drop_back();
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());
135 return make_error<StringError>("Unknown key: '" + Key + "'",
136 inconvertibleErrorCode());
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;
151 if (sys::fs::is_directory(Path, isPathDir))
157 Policy.MaxSizePercentageOfAvailableSpace =
158 std::min(Policy.MaxSizePercentageOfAvailableSpace, 100u);
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
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);
182 if (!Policy.Interval)
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");
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);
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;
207 // Walk the entire directory cache, looking for unused files.
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 any files not beginning with the string "llvmcache-". 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 if (!sys::path::filename(File->path()).startswith("llvmcache-"))
221 // Look at this file. If we can't stat it, there's nothing interesting
223 ErrorOr<sys::fs::basic_file_status> StatusOrErr = File->status();
225 LLVM_DEBUG(dbgs() << "Ignore " << File->path() << " (can't stat)\n");
229 // If the file hasn't been used recently enough, delete it
230 const auto FileAccessTime = StatusOrErr->getLastAccessedTime();
231 auto FileAge = CurrentTime - FileAccessTime;
232 if (Policy.Expiration != seconds(0) && FileAge > Policy.Expiration) {
233 LLVM_DEBUG(dbgs() << "Remove " << File->path() << " ("
234 << duration_cast<seconds>(FileAge).count()
236 sys::fs::remove(File->path());
240 // Leave it here for now, but add it to the list of size-based pruning.
241 TotalSize += StatusOrErr->getSize();
242 FileInfos.insert({FileAccessTime, StatusOrErr->getSize(), File->path()});
245 auto FileInfo = FileInfos.begin();
246 size_t NumFiles = FileInfos.size();
248 auto RemoveCacheFile = [&]() {
250 sys::fs::remove(FileInfo->Path);
252 TotalSize -= FileInfo->Size;
254 LLVM_DEBUG(dbgs() << " - Remove " << FileInfo->Path << " (size "
255 << FileInfo->Size << "), new occupancy is " << TotalSize
260 // Prune for number of files.
261 if (Policy.MaxSizeFiles)
262 while (NumFiles > Policy.MaxSizeFiles)
265 // Prune for size now if needed
266 if (Policy.MaxSizePercentageOfAvailableSpace > 0 || Policy.MaxSizeBytes > 0) {
267 auto ErrOrSpaceInfo = sys::fs::disk_space(Path);
268 if (!ErrOrSpaceInfo) {
269 report_fatal_error("Can't get available size");
271 sys::fs::space_info SpaceInfo = ErrOrSpaceInfo.get();
272 auto AvailableSpace = TotalSize + SpaceInfo.free;
274 if (Policy.MaxSizePercentageOfAvailableSpace == 0)
275 Policy.MaxSizePercentageOfAvailableSpace = 100;
276 if (Policy.MaxSizeBytes == 0)
277 Policy.MaxSizeBytes = AvailableSpace;
278 auto TotalSizeTarget = std::min<uint64_t>(
279 AvailableSpace * Policy.MaxSizePercentageOfAvailableSpace / 100ull,
280 Policy.MaxSizeBytes);
282 LLVM_DEBUG(dbgs() << "Occupancy: " << ((100 * TotalSize) / AvailableSpace)
284 << Policy.MaxSizePercentageOfAvailableSpace << "%, "
285 << Policy.MaxSizeBytes << " bytes\n");
287 // Remove the oldest accessed files first, till we get below the threshold.
288 while (TotalSize > TotalSizeTarget && FileInfo != FileInfos.end())