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/WithColor.h"
21 #include "llvm/Support/raw_ostream.h"
22
23 #define DEBUG_TYPE "cache-pruning"
24
25 #include <set>
26 #include <system_error>
27
28 using namespace llvm;
29
30 namespace {
31 struct FileInfo {
32 sys::TimePoint<> Time;
33 uint64_t Size;
34 std::string Path;
35
36 /// Used to determine which files to prune first. Also used to determine
37 /// set membership, so must take into account all fields.
operator <__anon941338bb0111::FileInfo38 bool operator<(const FileInfo &Other) const {
39 return std::tie(Time, Other.Size, Path) <
40 std::tie(Other.Time, Size, Other.Path);
41 }
42 };
43 } // anonymous namespace
44
45 /// Write a new timestamp file with the given path. This is used for the pruning
46 /// interval option.
writeTimestampFile(StringRef TimestampFile)47 static void writeTimestampFile(StringRef TimestampFile) {
48 std::error_code EC;
49 raw_fd_ostream Out(TimestampFile.str(), EC, sys::fs::OF_None);
50 }
51
parseDuration(StringRef Duration)52 static Expected<std::chrono::seconds> parseDuration(StringRef Duration) {
53 if (Duration.empty())
54 return make_error<StringError>("Duration must not be empty",
55 inconvertibleErrorCode());
56
57 StringRef NumStr = Duration.slice(0, Duration.size()-1);
58 uint64_t Num;
59 if (NumStr.getAsInteger(0, Num))
60 return make_error<StringError>("'" + NumStr + "' not an integer",
61 inconvertibleErrorCode());
62
63 switch (Duration.back()) {
64 case 's':
65 return std::chrono::seconds(Num);
66 case 'm':
67 return std::chrono::minutes(Num);
68 case 'h':
69 return std::chrono::hours(Num);
70 default:
71 return make_error<StringError>("'" + Duration +
72 "' must end with one of 's', 'm' or 'h'",
73 inconvertibleErrorCode());
74 }
75 }
76
77 Expected<CachePruningPolicy>
parseCachePruningPolicy(StringRef PolicyStr)78 llvm::parseCachePruningPolicy(StringRef PolicyStr) {
79 CachePruningPolicy Policy;
80 std::pair<StringRef, StringRef> P = {"", PolicyStr};
81 while (!P.second.empty()) {
82 P = P.second.split(':');
83
84 StringRef Key, Value;
85 std::tie(Key, Value) = P.first.split('=');
86 if (Key == "prune_interval") {
87 auto DurationOrErr = parseDuration(Value);
88 if (!DurationOrErr)
89 return DurationOrErr.takeError();
90 Policy.Interval = *DurationOrErr;
91 } else if (Key == "prune_after") {
92 auto DurationOrErr = parseDuration(Value);
93 if (!DurationOrErr)
94 return DurationOrErr.takeError();
95 Policy.Expiration = *DurationOrErr;
96 } else if (Key == "cache_size") {
97 if (Value.back() != '%')
98 return make_error<StringError>("'" + Value + "' must be a percentage",
99 inconvertibleErrorCode());
100 StringRef SizeStr = Value.drop_back();
101 uint64_t Size;
102 if (SizeStr.getAsInteger(0, Size))
103 return make_error<StringError>("'" + SizeStr + "' not an integer",
104 inconvertibleErrorCode());
105 if (Size > 100)
106 return make_error<StringError>("'" + SizeStr +
107 "' must be between 0 and 100",
108 inconvertibleErrorCode());
109 Policy.MaxSizePercentageOfAvailableSpace = Size;
110 } else if (Key == "cache_size_bytes") {
111 uint64_t Mult = 1;
112 switch (tolower(Value.back())) {
113 case 'k':
114 Mult = 1024;
115 Value = Value.drop_back();
116 break;
117 case 'm':
118 Mult = 1024 * 1024;
119 Value = Value.drop_back();
120 break;
121 case 'g':
122 Mult = 1024 * 1024 * 1024;
123 Value = Value.drop_back();
124 break;
125 }
126 uint64_t Size;
127 if (Value.getAsInteger(0, Size))
128 return make_error<StringError>("'" + Value + "' not an integer",
129 inconvertibleErrorCode());
130 Policy.MaxSizeBytes = Size * Mult;
131 } else if (Key == "cache_size_files") {
132 if (Value.getAsInteger(0, Policy.MaxSizeFiles))
133 return make_error<StringError>("'" + Value + "' not an integer",
134 inconvertibleErrorCode());
135 } else {
136 return make_error<StringError>("Unknown key: '" + Key + "'",
137 inconvertibleErrorCode());
138 }
139 }
140
141 return Policy;
142 }
143
144 /// Prune the cache of files that haven't been accessed in a long time.
pruneCache(StringRef Path,CachePruningPolicy Policy,const std::vector<std::unique_ptr<MemoryBuffer>> & Files)145 bool llvm::pruneCache(StringRef Path, CachePruningPolicy Policy,
146 const std::vector<std::unique_ptr<MemoryBuffer>> &Files) {
147 using namespace std::chrono;
148
149 if (Path.empty())
150 return false;
151
152 bool isPathDir;
153 if (sys::fs::is_directory(Path, isPathDir))
154 return false;
155
156 if (!isPathDir)
157 return false;
158
159 Policy.MaxSizePercentageOfAvailableSpace =
160 std::min(Policy.MaxSizePercentageOfAvailableSpace, 100u);
161
162 if (Policy.Expiration == seconds(0) &&
163 Policy.MaxSizePercentageOfAvailableSpace == 0 &&
164 Policy.MaxSizeBytes == 0 && Policy.MaxSizeFiles == 0) {
165 LLVM_DEBUG(dbgs() << "No pruning settings set, exit early\n");
166 // Nothing will be pruned, early exit
167 return false;
168 }
169
170 // Try to stat() the timestamp file.
171 SmallString<128> TimestampFile(Path);
172 sys::path::append(TimestampFile, "llvmcache.timestamp");
173 sys::fs::file_status FileStatus;
174 const auto CurrentTime = system_clock::now();
175 if (auto EC = sys::fs::status(TimestampFile, FileStatus)) {
176 if (EC == errc::no_such_file_or_directory) {
177 // If the timestamp file wasn't there, create one now.
178 writeTimestampFile(TimestampFile);
179 } else {
180 // Unknown error?
181 return false;
182 }
183 } else {
184 if (!Policy.Interval)
185 return false;
186 if (Policy.Interval != seconds(0)) {
187 // Check whether the time stamp is older than our pruning interval.
188 // If not, do nothing.
189 const auto TimeStampModTime = FileStatus.getLastModificationTime();
190 auto TimeStampAge = CurrentTime - TimeStampModTime;
191 if (TimeStampAge <= *Policy.Interval) {
192 LLVM_DEBUG(dbgs() << "Timestamp file too recent ("
193 << duration_cast<seconds>(TimeStampAge).count()
194 << "s old), do not prune.\n");
195 return false;
196 }
197 }
198 // Write a new timestamp file so that nobody else attempts to prune.
199 // There is a benign race condition here, if two processes happen to
200 // notice at the same time that the timestamp is out-of-date.
201 writeTimestampFile(TimestampFile);
202 }
203
204 // Keep track of files to delete to get below the size limit.
205 // Order by time of last use so that recently used files are preserved.
206 std::set<FileInfo> FileInfos;
207 uint64_t TotalSize = 0;
208
209 // Walk the entire directory cache, looking for unused files.
210 std::error_code EC;
211 SmallString<128> CachePathNative;
212 sys::path::native(Path, CachePathNative);
213 // Walk all of the files within this directory.
214 for (sys::fs::directory_iterator File(CachePathNative, EC), FileEnd;
215 File != FileEnd && !EC; File.increment(EC)) {
216 // Ignore filenames not beginning with "llvmcache-" or "Thin-". This
217 // includes the timestamp file as well as any files created by the user.
218 // This acts as a safeguard against data loss if the user specifies the
219 // wrong directory as their cache directory.
220 StringRef filename = sys::path::filename(File->path());
221 if (!filename.starts_with("llvmcache-") && !filename.starts_with("Thin-"))
222 continue;
223
224 // Look at this file. If we can't stat it, there's nothing interesting
225 // there.
226 ErrorOr<sys::fs::basic_file_status> StatusOrErr = File->status();
227 if (!StatusOrErr) {
228 LLVM_DEBUG(dbgs() << "Ignore " << File->path() << " (can't stat)\n");
229 continue;
230 }
231
232 // If the file hasn't been used recently enough, delete it
233 const auto FileAccessTime = StatusOrErr->getLastAccessedTime();
234 auto FileAge = CurrentTime - FileAccessTime;
235 if (Policy.Expiration != seconds(0) && FileAge > Policy.Expiration) {
236 LLVM_DEBUG(dbgs() << "Remove " << File->path() << " ("
237 << duration_cast<seconds>(FileAge).count()
238 << "s old)\n");
239 sys::fs::remove(File->path());
240 continue;
241 }
242
243 // Leave it here for now, but add it to the list of size-based pruning.
244 TotalSize += StatusOrErr->getSize();
245 FileInfos.insert({FileAccessTime, StatusOrErr->getSize(), File->path()});
246 }
247
248 auto FileInfo = FileInfos.begin();
249 size_t NumFiles = FileInfos.size();
250
251 auto RemoveCacheFile = [&]() {
252 // Remove the file.
253 sys::fs::remove(FileInfo->Path);
254 // Update size
255 TotalSize -= FileInfo->Size;
256 NumFiles--;
257 LLVM_DEBUG(dbgs() << " - Remove " << FileInfo->Path << " (size "
258 << FileInfo->Size << "), new occupancy is " << TotalSize
259 << "%\n");
260 ++FileInfo;
261 };
262
263 // files.size() is greater the number of inputs by one. However, a timestamp
264 // file is created and stored in the cache directory if --thinlto-cache-policy
265 // option is used. Therefore, files.size() is used as ActualNums.
266 const size_t ActualNums = Files.size();
267 if (Policy.MaxSizeFiles && ActualNums > Policy.MaxSizeFiles)
268 WithColor::warning()
269 << "ThinLTO cache pruning happens since the number of created files ("
270 << ActualNums << ") exceeds the maximum number of files ("
271 << Policy.MaxSizeFiles
272 << "); consider adjusting --thinlto-cache-policy\n";
273
274 // Prune for number of files.
275 if (Policy.MaxSizeFiles)
276 while (NumFiles > Policy.MaxSizeFiles)
277 RemoveCacheFile();
278
279 // Prune for size now if needed
280 if (Policy.MaxSizePercentageOfAvailableSpace > 0 || Policy.MaxSizeBytes > 0) {
281 auto ErrOrSpaceInfo = sys::fs::disk_space(Path);
282 if (!ErrOrSpaceInfo) {
283 report_fatal_error("Can't get available size");
284 }
285 sys::fs::space_info SpaceInfo = ErrOrSpaceInfo.get();
286 auto AvailableSpace = TotalSize + SpaceInfo.free;
287
288 if (Policy.MaxSizePercentageOfAvailableSpace == 0)
289 Policy.MaxSizePercentageOfAvailableSpace = 100;
290 if (Policy.MaxSizeBytes == 0)
291 Policy.MaxSizeBytes = AvailableSpace;
292 auto TotalSizeTarget = std::min<uint64_t>(
293 AvailableSpace * Policy.MaxSizePercentageOfAvailableSpace / 100ull,
294 Policy.MaxSizeBytes);
295
296 LLVM_DEBUG(dbgs() << "Occupancy: " << ((100 * TotalSize) / AvailableSpace)
297 << "% target is: "
298 << Policy.MaxSizePercentageOfAvailableSpace << "%, "
299 << Policy.MaxSizeBytes << " bytes\n");
300
301 size_t ActualSizes = 0;
302 for (const auto &File : Files)
303 if (File)
304 ActualSizes += File->getBufferSize();
305
306 if (ActualSizes > TotalSizeTarget)
307 WithColor::warning()
308 << "ThinLTO cache pruning happens since the total size of the cache "
309 "files consumed by the current link job ("
310 << ActualSizes << " bytes) exceeds maximum cache size ("
311 << TotalSizeTarget
312 << " bytes); consider adjusting --thinlto-cache-policy\n";
313
314 // Remove the oldest accessed files first, till we get below the threshold.
315 while (TotalSize > TotalSizeTarget && FileInfo != FileInfos.end())
316 RemoveCacheFile();
317 }
318 return true;
319 }
320