/// 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) {
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 =
time_point_cast<decltype(Policy.Interval)>(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 != seconds(0)) {
// Check whether the time stamp is older than our pruning interval.
// If not, do nothing.
const auto TimeStampModTime = time_point_cast<decltype(Policy.Interval)>(
FileStatus.getLastModificationTime());
auto TimeStampAge = CurrentTime - TimeStampModTime;
if (TimeStampAge <= Policy.Interval) {
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// notice at the same time that the timestamp is out-of-date.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 space. Needs to be kept ordered by size for determinism.
std::set<std::pair<uint64_t, std::string>> FileSizes;
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) {
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) {
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();
FileSizes.insert({StatusOrErr->getSize(), std::string(File->path())});
}
auto FileAndSize = FileSizes.rbegin();
size_t NumFiles = FileSizes.size();
auto RemoveCacheFile = [&]() {
// Remove the file.
sys::fs::remove(FileAndSize->second);
// Update size
TotalSize -= FileAndSize->first;
NumFiles--;
DEBUG(dbgs() << " - Remove " << FileAndSize->second << " (size "
<< FileAndSize->first << "), new occupancy is " << TotalSize
<< "%\n");
++FileAndSize;
};
// 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);
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 && FileAndSize != FileSizes.rend())
RemoveCacheFile();
}
return true;
}
