| //=- CachePruning.h - Helper to manage the pruning of a cache dir -*- C++ -*-=// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements pruning of a directory intended for cache storage, using |
| // various policies. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_SUPPORT_CACHE_PRUNING_H |
| #define LLVM_SUPPORT_CACHE_PRUNING_H |
| |
| #include "llvm/ADT/StringRef.h" |
| #include <chrono> |
| |
| namespace llvm { |
| |
| template <typename T> class Expected; |
| |
| /// Policy for the pruneCache() function. A default constructed |
| /// CachePruningPolicy provides a reasonable default policy. |
| struct CachePruningPolicy { |
| /// The pruning interval. This is intended to be used to avoid scanning the |
| /// directory too often. It does not impact the decision of which file to |
| /// prune. A value of 0 forces the scan to occur. A value of None disables |
| /// pruning. |
| llvm::Optional<std::chrono::seconds> Interval = std::chrono::seconds(1200); |
| |
| /// The expiration for a file. When a file hasn't been accessed for Expiration |
| /// seconds, it is removed from the cache. A value of 0 disables the |
| /// expiration-based pruning. |
| std::chrono::seconds Expiration = std::chrono::hours(7 * 24); // 1w |
| |
| /// The maximum size for the cache directory, in terms of percentage of the |
| /// available space on the disk. Set to 100 to indicate no limit, 50 to |
| /// indicate that the cache size will not be left over half the available disk |
| /// space. A value over 100 will be reduced to 100. A value of 0 disables the |
| /// percentage size-based pruning. |
| unsigned MaxSizePercentageOfAvailableSpace = 75; |
| |
| /// The maximum size for the cache directory in bytes. A value over the amount |
| /// of available space on the disk will be reduced to the amount of available |
| /// space. A value of 0 disables the absolute size-based pruning. |
| uint64_t MaxSizeBytes = 0; |
| |
| /// The maximum number of files in the cache directory. A value of 0 disables |
| /// the number of files based pruning. |
| /// |
| /// This defaults to 1000000 because with that many files there are |
| /// diminishing returns on the effectiveness of the cache. Some systems have a |
| /// limit on total number of files, and some also limit the number of files |
| /// per directory, such as Linux ext4, with the default setting (block size is |
| /// 4096 and large_dir disabled), there is a per-directory entry limit of |
| /// 508*510*floor(4096/(40+8))~=20M for average filename length of 40. |
| uint64_t MaxSizeFiles = 1000000; |
| }; |
| |
| /// Parse the given string as a cache pruning policy. Defaults are taken from a |
| /// default constructed CachePruningPolicy object. |
| /// For example: "prune_interval=30s:prune_after=24h:cache_size=50%" |
| /// which means a pruning interval of 30 seconds, expiration time of 24 hours |
| /// and maximum cache size of 50% of available disk space. |
| Expected<CachePruningPolicy> parseCachePruningPolicy(StringRef PolicyStr); |
| |
| /// Peform pruning using the supplied policy, returns true if pruning |
| /// occurred, i.e. if Policy.Interval was expired. |
| /// |
| /// As a safeguard against data loss if the user specifies the wrong directory |
| /// as their cache directory, this function will ignore files not matching the |
| /// pattern "llvmcache-*". |
| bool pruneCache(StringRef Path, CachePruningPolicy Policy); |
| |
| } // namespace llvm |
| |
| #endif |