LLVM  8.0.0svn
CachePruning.h
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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.
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.
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.
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
uint64_t MaxSizeBytes
The maximum size for the cache directory in bytes.
Definition: CachePruning.h:49
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
Interval Class - An Interval is a set of nodes defined such that every node in the interval has all o...
Definition: Interval.h:37
std::chrono::seconds Expiration
The expiration for a file.
Definition: CachePruning.h:37
uint64_t MaxSizeFiles
The maximum number of files in the cache directory.
Definition: CachePruning.h:60
Tagged union holding either a T or a Error.
Definition: CachePruning.h:23
unsigned MaxSizePercentageOfAvailableSpace
The maximum size for the cache directory, in terms of percentage of the available space on the disk...
Definition: CachePruning.h:44
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:27
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49