LLVM  9.0.0svn
CachePruning.h
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1 //=- CachePruning.h - Helper to manage the pruning of a cache dir -*- C++ -*-=//
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 pruning of a directory intended for cache storage, using
10 // various policies.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_SUPPORT_CACHE_PRUNING_H
15 #define LLVM_SUPPORT_CACHE_PRUNING_H
16 
17 #include "llvm/ADT/StringRef.h"
18 #include <chrono>
19 
20 namespace llvm {
21 
22 template <typename T> class Expected;
23 
24 /// Policy for the pruneCache() function. A default constructed
25 /// CachePruningPolicy provides a reasonable default policy.
27  /// The pruning interval. This is intended to be used to avoid scanning the
28  /// directory too often. It does not impact the decision of which file to
29  /// prune. A value of 0 forces the scan to occur. A value of None disables
30  /// pruning.
31  llvm::Optional<std::chrono::seconds> Interval = std::chrono::seconds(1200);
32 
33  /// The expiration for a file. When a file hasn't been accessed for Expiration
34  /// seconds, it is removed from the cache. A value of 0 disables the
35  /// expiration-based pruning.
36  std::chrono::seconds Expiration = std::chrono::hours(7 * 24); // 1w
37 
38  /// The maximum size for the cache directory, in terms of percentage of the
39  /// available space on the disk. Set to 100 to indicate no limit, 50 to
40  /// indicate that the cache size will not be left over half the available disk
41  /// space. A value over 100 will be reduced to 100. A value of 0 disables the
42  /// percentage size-based pruning.
44 
45  /// The maximum size for the cache directory in bytes. A value over the amount
46  /// of available space on the disk will be reduced to the amount of available
47  /// space. A value of 0 disables the absolute size-based pruning.
48  uint64_t MaxSizeBytes = 0;
49 
50  /// The maximum number of files in the cache directory. A value of 0 disables
51  /// the number of files based pruning.
52  ///
53  /// This defaults to 1000000 because with that many files there are
54  /// diminishing returns on the effectiveness of the cache. Some systems have a
55  /// limit on total number of files, and some also limit the number of files
56  /// per directory, such as Linux ext4, with the default setting (block size is
57  /// 4096 and large_dir disabled), there is a per-directory entry limit of
58  /// 508*510*floor(4096/(40+8))~=20M for average filename length of 40.
59  uint64_t MaxSizeFiles = 1000000;
60 };
61 
62 /// Parse the given string as a cache pruning policy. Defaults are taken from a
63 /// default constructed CachePruningPolicy object.
64 /// For example: "prune_interval=30s:prune_after=24h:cache_size=50%"
65 /// which means a pruning interval of 30 seconds, expiration time of 24 hours
66 /// and maximum cache size of 50% of available disk space.
68 
69 /// Peform pruning using the supplied policy, returns true if pruning
70 /// occurred, i.e. if Policy.Interval was expired.
71 ///
72 /// As a safeguard against data loss if the user specifies the wrong directory
73 /// as their cache directory, this function will ignore files not matching the
74 /// pattern "llvmcache-*".
75 bool pruneCache(StringRef Path, CachePruningPolicy Policy);
76 
77 } // namespace llvm
78 
79 #endif
uint64_t MaxSizeBytes
The maximum size for the cache directory in bytes.
Definition: CachePruning.h:48
This class represents lattice values for constants.
Definition: AllocatorList.h:23
Interval Class - An Interval is a set of nodes defined such that every node in the interval has all o...
Definition: Interval.h:36
std::chrono::seconds Expiration
The expiration for a file.
Definition: CachePruning.h:36
uint64_t MaxSizeFiles
The maximum number of files in the cache directory.
Definition: CachePruning.h:59
Tagged union holding either a T or a Error.
Definition: CachePruning.h:22
unsigned MaxSizePercentageOfAvailableSpace
The maximum size for the cache directory, in terms of percentage of the available space on the disk...
Definition: CachePruning.h:43
Expected< CachePruningPolicy > parseCachePruningPolicy(StringRef PolicyStr)
Parse the given string as a cache pruning policy.
bool pruneCache(StringRef Path, CachePruningPolicy Policy)
Peform pruning using the supplied policy, returns true if pruning occurred, i.e.
Policy for the pruneCache() function.
Definition: CachePruning.h:26
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48