1 //=- CachePruning.h - Helper to manage the pruning of a cache dir -*- C++ -*-=// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements pruning of a directory intended for cache storage, using 11 // various policies. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_SUPPORT_CACHE_PRUNING_H 16 #define LLVM_SUPPORT_CACHE_PRUNING_H 17 18 #include "llvm/ADT/StringRef.h" 19 #include <chrono> 20 21 namespace llvm { 22 23 template <typename T> class Expected; 24 25 /// Policy for the pruneCache() function. A default constructed 26 /// CachePruningPolicy provides a reasonable default policy. 27 struct CachePruningPolicy { 28 /// The pruning interval. This is intended to be used to avoid scanning the 29 /// directory too often. It does not impact the decision of which file to 30 /// prune. A value of 0 forces the scan to occur. A value of None disables 31 /// pruning. 32 llvm::Optional<std::chrono::seconds> Interval = std::chrono::seconds(1200); 33 34 /// The expiration for a file. When a file hasn't been accessed for Expiration 35 /// seconds, it is removed from the cache. A value of 0 disables the 36 /// expiration-based pruning. 37 std::chrono::seconds Expiration = std::chrono::hours(7 * 24); // 1w 38 39 /// The maximum size for the cache directory, in terms of percentage of the 40 /// available space on the disk. Set to 100 to indicate no limit, 50 to 41 /// indicate that the cache size will not be left over half the available disk 42 /// space. A value over 100 will be reduced to 100. A value of 0 disables the 43 /// percentage size-based pruning. 44 unsigned MaxSizePercentageOfAvailableSpace = 75; 45 46 /// The maximum size for the cache directory in bytes. A value over the amount 47 /// of available space on the disk will be reduced to the amount of available 48 /// space. A value of 0 disables the absolute size-based pruning. 49 uint64_t MaxSizeBytes = 0; 50 51 /// The maximum number of files in the cache directory. A value of 0 disables 52 /// the number of files based pruning. 53 /// 54 /// This defaults to 1000000 because with that many files there are 55 /// diminishing returns on the effectiveness of the cache. Some systems have a 56 /// limit on total number of files, and some also limit the number of files 57 /// per directory, such as Linux ext4, with the default setting (block size is 58 /// 4096 and large_dir disabled), there is a per-directory entry limit of 59 /// 508*510*floor(4096/(40+8))~=20M for average filename length of 40. 60 uint64_t MaxSizeFiles = 1000000; 61 }; 62 63 /// Parse the given string as a cache pruning policy. Defaults are taken from a 64 /// default constructed CachePruningPolicy object. 65 /// For example: "prune_interval=30s:prune_after=24h:cache_size=50%" 66 /// which means a pruning interval of 30 seconds, expiration time of 24 hours 67 /// and maximum cache size of 50% of available disk space. 68 Expected<CachePruningPolicy> parseCachePruningPolicy(StringRef PolicyStr); 69 70 /// Peform pruning using the supplied policy, returns true if pruning 71 /// occurred, i.e. if Policy.Interval was expired. 72 /// 73 /// As a safeguard against data loss if the user specifies the wrong directory 74 /// as their cache directory, this function will ignore files not matching the 75 /// pattern "llvmcache-*". 76 bool pruneCache(StringRef Path, CachePruningPolicy Policy); 77 78 } // namespace llvm 79 80 #endif 81
