GCC Code Coverage Report

Directory: cvmfs/
File: cvmfs/lru.h
Date: 2025-11-09 02:35:23
Exec Total Coverage
Lines: 320 324 98.8%
Branches: 135 246 54.9%
Line Branch Exec Source
1 /**
2 * This file is part of the CernVM File System.
3 *
4 * This class provides an Least Recently Used (LRU) cache for arbitrary data
5 * It stores Key-Value pairs of arbitrary data types in a hash table and
6 * automatically deletes the entries which are least touched in the last time
7 * to prevent the structure from growing beyond a given maximal cache size.
8 * The cache uses a hand crafted memory allocator to use memory efficiently
9 *
10 * Hash functions have to be provided. They should return an equal distribution
11 * of keys in uint32_t. In addition, a special key has to be provided that is
12 * used to mark "empty" elements in the hash table.
13 *
14 * The cache size has to be a multiply of 64.
15 *
16 * usage:
17 * // 100 entries, -1 special key
18 * LruCache<int, string> cache(100, -1, hasher_int);
19 *
20 * // Inserting some stuff
21 * cache.insert(42, "fourtytwo");
22 * cache.insert(2, "small prime number");
23 * cache.insert(1337, "leet");
24 *
25 * // Trying to retrieve a value
26 * int result;
27 * if (cache.lookup(21, result)) {
28 * cout << "cache hit: " << result << endl;
29 * } else {
30 * cout << "cache miss" << endl;
31 * }
32 *
33 * cache.drop(); // Empty the cache
34 */
35
36 #ifndef CVMFS_LRU_H_
37 #define CVMFS_LRU_H_
38
39 // If defined the cache is secured by a posix mutex
40 #define LRU_CACHE_THREAD_SAFE
41
42 #include <stdint.h>
43
44 #include <algorithm>
45 #include <cassert>
46 #include <cstring>
47 #include <functional>
48 #include <map>
49 #include <string>
50
51 #include "smallhash.h"
52 #include "statistics.h"
53 #include "util/atomic.h"
54 #include "util/platform.h"
55 #include "util/single_copy.h"
56 #include "util/smalloc.h"
57
58 namespace lru {
59
60 /**
61 * Counting of cache operations.
62 */
63 struct Counters {
64 perf::Counter *sz_size;
65 perf::Counter *n_hit;
66 perf::Counter *n_miss;
67 perf::Counter *n_insert;
68 perf::Counter *n_insert_negative;
69 uint64_t num_collisions;
70 uint32_t max_collisions;
71 perf::Counter *n_update;
72 perf::Counter *n_update_value;
73 perf::Counter *n_replace;
74 perf::Counter *n_forget;
75 perf::Counter *n_drop;
76 perf::Counter *sz_allocated;
77
78 2396 explicit Counters(perf::StatisticsTemplate statistics) {
79
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 sz_size = statistics.RegisterTemplated("sz_size", "Total size");
80 2396 num_collisions = 0;
81 2396 max_collisions = 0;
82
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 n_hit = statistics.RegisterTemplated("n_hit", "Number of hits");
83
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 n_miss = statistics.RegisterTemplated("n_miss", "Number of misses");
84
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 n_insert = statistics.RegisterTemplated("n_insert", "Number of inserts");
85
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 n_insert_negative = statistics.RegisterTemplated(
86 "n_insert_negative", "Number of negative inserts");
87
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 n_update = statistics.RegisterTemplated("n_update", "Number of updates");
88
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 n_update_value = statistics.RegisterTemplated("n_update_value",
89 "Number of value changes");
90
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 n_replace = statistics.RegisterTemplated("n_replace", "Number of replaces");
91
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 n_forget = statistics.RegisterTemplated("n_forget", "Number of forgets");
92
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 n_drop = statistics.RegisterTemplated("n_drop", "Number of drops");
93
3/6
✓ Branch 2 taken 2396 times.
✗ Branch 3 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
✓ Branch 9 taken 2396 times.
✗ Branch 10 not taken.
 2396 sz_allocated = statistics.RegisterTemplated("sz_allocated",
94 "Number of allocated bytes ");
95 2396 }
96 };
97
98
99 /**
100 * Template class to create a LRU cache
101 * @param Key type of the key values
102 * @param Value type of the value values
103 */
104 template<class Key, class Value>
105 class LruCache : SingleCopy {
106 private:
107 // Forward declarations of private internal data structures
108 template<class T>
109 class ListEntry;
110 template<class T>
111 class ListEntryHead;
112 template<class T>
113 class ListEntryContent;
114 template<class M>
115 class MemoryAllocator;
116
117 // Helpers to get the template magic right
118 typedef ListEntryContent<Key> ConcreteListEntryContent;
119 typedef MemoryAllocator<ConcreteListEntryContent> ConcreteMemoryAllocator;
120
121 /**
122 * This structure wraps the user data and relates it to the LRU list entry
123 */
124 typedef struct {
125 ListEntryContent<Key> *list_entry;
126 Value value;
127 } CacheEntry;
128
129 // static uint64_t GetEntrySize() { return sizeof(Key) + sizeof(Value); }
130
131 /**
132 * A special purpose memory allocator for the cache entries.
133 * It allocates enough memory for the maximal number of cache entries at
134 * startup, and assigns new ListEntryContent objects to a free spot in this
135 * memory pool (by overriding the 'new' and 'delete' operators of
136 * ListEntryContent).
137 *
138 * @param T the type of object to be allocated by this MemoryAllocator
139 */
140 template<class T>
141 class MemoryAllocator : SingleCopy {
142 public:
143 /**
144 * Creates a MemoryAllocator to handle a memory pool for objects of type T
145 * @param num_slots the number of slots to be allocated for the given
146 * datatype T
147 */
148 3427 explicit MemoryAllocator(const unsigned int num_slots) {
149 // how many bitmap chunks (chars) do we need?
150 3427 const unsigned int num_bytes_bitmap = num_slots / 8;
151 3427 bits_per_block_ = 8 * sizeof(bitmap_[0]);
152
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 2396 times.
 3427 assert((num_slots % bits_per_block_) == 0);
153
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 2396 times.
 3427 assert(num_slots >= 2 * bits_per_block_);
154
155 // How much actual memory do we need?
156 3427 const unsigned int num_bytes_memory = sizeof(T) * num_slots;
157
158 // Allocate zero'd memory
159 3427 bitmap_ = reinterpret_cast<uint64_t *>(scalloc(num_bytes_bitmap, 1));
160 3427 memory_ = reinterpret_cast<T *>(scalloc(num_bytes_memory, 1));
161
162 // Create initial state
163 3427 num_slots_ = num_slots;
164 3427 num_free_slots_ = num_slots;
165 3427 next_free_slot_ = 0;
166 3427 bytes_allocated_ = num_bytes_bitmap + num_bytes_memory;
167 3427 }
168
169 /**
170 * Number of bytes for a single entry
171 */
172 1848 static double GetEntrySize() {
173 1848 return static_cast<double>(sizeof(T)) + 1.0 / 8.0;
174 }
175
176 /**
177 * The memory allocator also frees all allocated data
178 */
179 4788 virtual ~MemoryAllocator() {
180 4788 free(bitmap_);
181 4788 free(memory_);
182 }
183
184 /**
185 * Check if the memory pool is full.
186 * @return true if all slots are occupied, otherwise false
187 */
188 186516 inline bool IsFull() const { return num_free_slots_ == 0; }
189
190 93258 T *Construct(const T object) {
191 93258 T *mem = Allocate();
192
1/2
✓ Branch 0 taken 92960 times.
✗ Branch 1 not taken.
 93258 if (mem != NULL) {
193
1/2
✓ Branch 2 taken 92960 times.
✗ Branch 3 not taken.
 93258 new (static_cast<void *>(mem)) T(object);
194 }
195 93258 return mem;
196 }
197
198 93254 void Destruct(T *object) {
199 93254 object->~T();
200 93254 Deallocate(object);
201 93254 }
202
203 /**
204 * Allocate a slot and returns a pointer to the memory.
205 * @return a pointer to a chunk of the memory pool
206 */
207 93258 T *Allocate() {
208
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 92960 times.
 93258 if (this->IsFull())
209 ✗ return NULL;
210
211 // Allocate a slot
212 93258 this->SetBit(next_free_slot_);
213 93258 --num_free_slots_;
214 93258 T *slot = memory_ + next_free_slot_;
215
216 // Find a new free slot if there are some left
217
2/2
✓ Branch 1 taken 72514 times.
✓ Branch 2 taken 20446 times.
 93258 if (!this->IsFull()) {
218 72812 unsigned bitmap_block = next_free_slot_ / bits_per_block_;
219
2/2
✓ Branch 0 taken 1009 times.
✓ Branch 1 taken 72514 times.
 73821 while (~bitmap_[bitmap_block] == 0)
220 1009 bitmap_block = (bitmap_block + 1) % (num_slots_ / bits_per_block_);
221 // TODO(jblomer): faster search inside the int
222 72812 next_free_slot_ = bitmap_block * bits_per_block_;
223
2/2
✓ Branch 1 taken 2202917 times.
✓ Branch 2 taken 72514 times.
 2276375 while (this->GetBit(next_free_slot_))
224 2203563 next_free_slot_++;
225 }
226
227 93258 return slot;
228 }
229
230 /**
231 * Free a given slot in the memory pool
232 * @param slot a pointer to the slot be freed
233 */
234 93254 void Deallocate(T *slot) {
235 // Check if given slot is in bounds
236
2/4
✓ Branch 0 taken 92956 times.
✗ Branch 1 not taken.
✓ Branch 2 taken 92956 times.
✗ Branch 3 not taken.
 93254 assert((slot >= memory_) && (slot <= memory_ + num_slots_));
237
238 // Get position of slot
239 93254 const unsigned int position = slot - memory_;
240
241 // Check if slot was already freed
242
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 92956 times.
 93254 assert(this->GetBit(position));
243
244 // Free slot, save the position of this slot as free (faster reallocation)
245 93254 this->UnsetBit(position);
246 93254 next_free_slot_ = position;
247 93254 ++num_free_slots_;
248 93254 }
249
250 3469 uint64_t bytes_allocated() { return bytes_allocated_; }
251
252 private:
253 /**
254 * Check a bit in the internal allocation bitmap.
255 * @param position the position to check
256 * @return true if bit is set, otherwise false
257 */
258 2369629 inline bool GetBit(const unsigned position) {
259
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 2368387 times.
 2369629 assert(position < num_slots_);
260 2369629 return ((bitmap_[position / bits_per_block_]
261 2369629 & (uint64_t(1) << (position % bits_per_block_)))
262 2369629 != 0);
263 }
264
265 /**
266 * set a bit in the internal allocation bitmap
267 * @param position the number of the bit to be set
268 */
269 93258 inline void SetBit(const unsigned position) {
270
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 92960 times.
 93258 assert(position < num_slots_);
271 93258 bitmap_[position / bits_per_block_] |= uint64_t(1)
272 93258 << (position % bits_per_block_);
273 93258 }
274
275 /**
276 * Clear a bit in the internal allocation bitmap
277 * @param position the number of the bit to be cleared
278 */
279 93254 inline void UnsetBit(const unsigned position) {
280
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 92956 times.
 93254 assert(position < num_slots_);
281 93254 bitmap_[position / bits_per_block_] &= ~(uint64_t(1)
282 93254 << (position % bits_per_block_));
283 93254 }
284
285 unsigned int num_slots_; /**< Overall number of slots in memory pool. */
286 unsigned int num_free_slots_; /**< Current number of free slots left. */
287 unsigned int next_free_slot_; /**< Position of next free slot in pool. */
288 uint64_t bytes_allocated_;
289 uint64_t *bitmap_; /**< A bitmap to mark slots as allocated. */
290 unsigned bits_per_block_;
291 T *memory_; /**< The memory pool, array of Ms. */
292 };
293
294
295 /**
296 * Internal LRU list entry, to maintain the doubly linked list.
297 * The list keeps track of the least recently used keys in the cache.
298 */
299 template<class T>
300 class ListEntry {
301 friend class LruCache;
302
303 public:
304 /**
305 * Create a new list entry as lonely, both next and prev pointing to this.
306 */
307 96685 ListEntry() {
308 96685 this->next = this;
309 96685 this->prev = this;
310 96685 }
311
312 93258 ListEntry(const ListEntry<T> &other) {
313
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 92960 times.
 93258 next = (other.next == &other) ? this : other.next;
314
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 92960 times.
 93258 prev = (other.prev == &other) ? this : other.prev;
315 93258 }
316
317 376620 virtual ~ListEntry() { }
318
319 /**
320 * Checks if the ListEntry is the list head
321 * @return true if ListEntry is list head otherwise false
322 */
323 virtual bool IsListHead() const = 0;
324
325 /**
326 * A lonely ListEntry has no connection to other elements.
327 * @return true if ListEntry is lonely otherwise false
328 */
329
3/4
✓ Branch 0 taken 712950 times.
✓ Branch 1 taken 1999026 times.
✓ Branch 2 taken 712950 times.
✗ Branch 3 not taken.
 2713416 bool IsLonely() const { return (this->next == this && this->prev == this); }
330
331 ListEntry<T> *next; /**< Pointer to next element in the list. */
332 ListEntry<T> *prev; /**< Pointer to previous element in the list. */
333
334 protected:
335 /**
336 * Insert a given ListEntry after this one.
337 * @param entry the ListEntry to insert after this one
338 */
339 inline void InsertAsSuccessor(ListEntryContent<T> *entry) {
340 assert(entry->IsLonely());
341
342 // Mount the new element between this and this->next
343 entry->next = this->next;
344 entry->prev = this;
345
346 // Fix pointers of existing list elements
347 this->next->prev = entry;
348 this->next = entry;
349 assert(!entry->IsLonely());
350 }
351
352 /**
353 * Insert a given ListEntry in front of this one
354 * @param entry the ListEntry to insert in front of this one
355 */
356 713459 inline void InsertAsPredecessor(ListEntryContent<T> *entry) {
357
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 712950 times.
 713459 assert(entry->IsLonely());
358
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 712950 times.
 713459 assert(!entry->IsListHead());
359
360 // Mount the new element between this and this->prev
361 713459 entry->next = this;
362 713459 entry->prev = this->prev;
363
364 // Fix pointers of existing list elements
365 713459 this->prev->next = entry;
366 713459 this->prev = entry;
367
368
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 712950 times.
 713459 assert(!entry->IsLonely());
369 713459 }
370
371 /**
372 * Remove this element from it's list.
373 * The function connects this->next with this->prev leaving the list
374 * in a consistent state. The ListEntry itself is lonely afterwards,
375 * but not deleted.
376 */
377 virtual void RemoveFromList() = 0;
378
379 private:
380 // No assignment operator (enforced by linker error)
381 ListEntry<T> &operator=(const ListEntry<T> &other);
382 }; // template<class T> class ListEntry
383
384 /**
385 * Specialized ListEntry to contain a data entry of type T
386 */
387 template<class T>
388 class ListEntryContent : public ListEntry<T> {
389 public:
390
1/2
✓ Branch 2 taken 5922 times.
✗ Branch 3 not taken.
 93258 explicit ListEntryContent(T content) { content_ = content; }
391
392 816938 inline bool IsListHead() const { return false; }
393 30532 inline T content() const { return content_; }
394
395 /**
396 * See ListEntry base class.
397 */
398 645915 inline void RemoveFromList() {
399
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 645704 times.
 645915 assert(!this->IsLonely());
400
401 // Remove this from list
402 645915 this->prev->next = this->next;
403 645915 this->next->prev = this->prev;
404
405 // Make this lonely
406 645915 this->next = this;
407 645915 this->prev = this;
408 645915 }
409
410 private:
411 T content_; /**< The data content of this ListEntry */
412 };
413
414 /**
415 * Specialized ListEntry to form a list head.
416 * Every list has exactly one list head which is also the entry point
417 * in the list. It is used to manipulate the list.
418 */
419 template<class T>
420 class ListEntryHead : public ListEntry<T> {
421 public:
422 3427 explicit ListEntryHead(ConcreteMemoryAllocator *allocator)
423 3427 : allocator_(allocator) { }
424
425 4788 virtual ~ListEntryHead() { this->clear(); }
426
427 /**
428 * Remove all entries from the list.
429 * ListEntry objects are deleted but contained data keeps available
430 */
431 3467 void clear() {
432 // Delete all list entries
433 3467 ListEntry<T> *entry = this->next;
434 ListEntry<T> *delete_me;
435
2/2
✓ Branch 1 taken 67242 times.
✓ Branch 2 taken 2436 times.
 71007 while (!entry->IsListHead()) {
436 67540 delete_me = entry;
437 67540 entry = entry->next;
438 67540 allocator_->Destruct(
439 static_cast<ConcreteListEntryContent *>(delete_me));
440 }
441
442 // Reset the list to lonely
443 3467 this->next = this;
444 3467 this->prev = this;
445 3467 }
446
447 3568 inline bool IsListHead() const { return true; }
448 20382 inline bool IsEmpty() const { return this->IsLonely(); }
449
450 /**
451 * Push a new data object to the end of the list.
452 * @param the data object to insert
453 * @return the ListEntryContent structure wrapped around the data object
454 */
455 93258 inline ListEntryContent<T> *PushBack(T content) {
456
1/2
✓ Branch 1 taken 92960 times.
✗ Branch 2 not taken.
 93258 ListEntryContent<T> *new_entry = allocator_->Construct(
457 186516 ListEntryContent<T>(content));
458 93258 this->InsertAsPredecessor(new_entry);
459 93258 return new_entry;
460 }
461
462 /**
463 * Pop the first object of the list.
464 * The object is returned and removed from the list
465 * @return the data object which resided in the first list entry
466 */
467 20382 inline T PopFront() {
468
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 20382 times.
 20382 assert(!this->IsEmpty());
469 20382 return Pop(this->next);
470 }
471
472 /**
473 * Take a list entry out of it's list and reinsert at the end of this list.
474 * @param the ListEntry to be moved to the end of this list
475 */
476 620201 inline void MoveToBack(ListEntryContent<T> *entry) {
477
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 619990 times.
 620201 assert(!entry->IsLonely());
478
479 620201 entry->RemoveFromList();
480 620201 this->InsertAsPredecessor(entry);
481 620201 }
482
483 /**
484 * See ListEntry base class
485 */
486 ✗ inline void RemoveFromList() { assert(false); }
487
488 private:
489 /**
490 * Pop a ListEntry from the list (arbitrary position).
491 * The given ListEntry is removed from the list, deleted and it's
492 * data content is returned
493 * @param popped_entry the entry to be popped
494 * @return the data object of the popped ListEntry
495 */
496 20382 inline T Pop(ListEntry<T> *popped_entry) {
497
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 20382 times.
 20382 assert(!popped_entry->IsListHead());
498
499 20382 ListEntryContent<T> *popped = (ListEntryContent<T> *)popped_entry;
500 20382 popped->RemoveFromList();
501 20382 T result = popped->content();
502 20382 allocator_->Destruct(
503 static_cast<ConcreteListEntryContent *>(popped_entry));
504 20382 return result;
505 }
506
507 private:
508 ConcreteMemoryAllocator *allocator_;
509 };
510
511 public: // LruCache
512 /**
513 * Create a new LRU cache object
514 * @param cache_size the maximal size of the cache
515 */
516 3427 LruCache(const unsigned cache_size,
517 const Key &empty_key,
518 uint32_t (*hasher)(const Key &key),
519 perf::StatisticsTemplate statistics)
520
1/2
✓ Branch 1 taken 2396 times.
✗ Branch 2 not taken.
 3427 : counters_(statistics)
521 3427 , pause_(false)
522 3427 , cache_gauge_(0)
523 3427 , cache_size_(cache_size)
524 3427 , allocator_(cache_size)
525
2/4
✓ Branch 3 taken 2396 times.
✗ Branch 4 not taken.
✓ Branch 6 taken 2396 times.
✗ Branch 7 not taken.
 6854 , lru_list_(&allocator_) {
526
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 2396 times.
 3427 assert(cache_size > 0);
527
528 3427 counters_.sz_size->Set(cache_size_);
529 3427 filter_entry_ = NULL;
530 // cache_ = Cache(cache_size_);
531
1/2
✓ Branch 1 taken 2396 times.
✗ Branch 2 not taken.
 3427 cache_.Init(cache_size_, empty_key, hasher);
532 3427 perf::Xadd(counters_.sz_allocated,
533 3427 allocator_.bytes_allocated() + cache_.bytes_allocated());
534
535 #ifdef LRU_CACHE_THREAD_SAFE
536 3427 const int retval = pthread_mutex_init(&lock_, NULL);
537
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 2396 times.
 3427 assert(retval == 0);
538 #endif
539 3427 }
540
541 1848 static double GetEntrySize() {
542 1848 return SmallHashFixed<Key, CacheEntry>::GetEntrySize()
543 1848 + ConcreteMemoryAllocator::GetEntrySize();
544 }
545
546 4788 virtual ~LruCache() {
547 #ifdef LRU_CACHE_THREAD_SAFE
548 4788 pthread_mutex_destroy(&lock_);
549 #endif
550 }
551
552 /**
553 * Insert a new key-value pair to the list.
554 * If the cache is already full, the least recently used object is removed;
555 * afterwards the new object is inserted.
556 * If the object is already present it is updated and moved back to the end
557 * of the list
558 * @param key the key where the value is saved
559 * @param value the value of the cache entry
560 * @return true on insert, false on update
561 */
562 380939 virtual bool Insert(const Key &key, const Value &value) {
563 380939 this->Lock();
564
2/2
✓ Branch 0 taken 40 times.
✓ Branch 1 taken 380601 times.
 380939 if (pause_) {
565 40 Unlock();
566 40 return false;
567 }
568
569
1/2
✓ Branch 1 taken 293365 times.
✗ Branch 2 not taken.
 380899 CacheEntry entry;
570
571 // Check if we have to update an existent entry
572
3/4
✓ Branch 1 taken 380601 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 287641 times.
✓ Branch 4 taken 92960 times.
 380899 if (this->DoLookup(key, &entry)) {
573 287641 perf::Inc(counters_.n_update);
574
1/2
✓ Branch 1 taken 198 times.
✗ Branch 2 not taken.
 287641 entry.value = value;
575
1/2
✓ Branch 1 taken 287641 times.
✗ Branch 2 not taken.
 287641 cache_.Insert(key, entry);
576
1/2
✓ Branch 1 taken 287641 times.
✗ Branch 2 not taken.
 287641 this->Touch(entry);
577 287641 this->Unlock();
578 287641 return false;
579 }
580
581 93258 perf::Inc(counters_.n_insert);
582 // Check if we have to make some space in the cache a
583
2/2
✓ Branch 1 taken 20382 times.
✓ Branch 2 taken 72578 times.
 93258 if (this->IsFull())
584
1/2
✓ Branch 1 taken 20382 times.
✗ Branch 2 not taken.
 20382 this->DeleteOldest();
585
586
1/2
✓ Branch 1 taken 92960 times.
✗ Branch 2 not taken.
 93258 entry.list_entry = lru_list_.PushBack(key);
587
1/2
✓ Branch 1 taken 87336 times.
✗ Branch 2 not taken.
 93258 entry.value = value;
588
589
1/2
✓ Branch 1 taken 92960 times.
✗ Branch 2 not taken.
 93258 cache_.Insert(key, entry);
590 93258 cache_gauge_++;
591
592 93258 Unlock();
593 93258 return true;
594 87832 }
595
596
597 /**
598 * Updates object and moves back to the end of the list. The object must be
599 * present.
600 */
601 22 virtual void Update(const Key &key) {
602 22 Lock();
603 // Is not called from the client, only from the cache plugin
604
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 22 times.
 22 assert(!pause_);
605
0/2
✗ Branch 1 not taken.
✗ Branch 2 not taken.
 22 CacheEntry entry;
606
1/2
✓ Branch 1 taken 22 times.
✗ Branch 2 not taken.
 22 const bool retval = DoLookup(key, &entry);
607
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 22 times.
 22 assert(retval);
608 22 perf::Inc(counters_.n_update);
609
1/2
✓ Branch 1 taken 22 times.
✗ Branch 2 not taken.
 22 Touch(entry);
610 22 Unlock();
611 22 }
612
613
614 /**
615 * Changes the value of an entry in the LRU cache without updating the LRU
616 * order.
617 */
618 66 virtual bool UpdateValue(const Key &key, const Value &value) {
619 66 this->Lock();
620
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 66 times.
 66 if (pause_) {
621 ✗ Unlock();
622 ✗ return false;
623 }
624
625
0/2
✗ Branch 1 not taken.
✗ Branch 2 not taken.
 66 CacheEntry entry;
626
3/4
✓ Branch 1 taken 66 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 22 times.
✓ Branch 4 taken 44 times.
 66 if (!this->DoLookup(key, &entry)) {
627 22 this->Unlock();
628 22 return false;
629 }
630
631 44 perf::Inc(counters_.n_update_value);
632
1/2
✓ Branch 1 taken 44 times.
✗ Branch 2 not taken.
 44 entry.value = value;
633
1/2
✓ Branch 1 taken 44 times.
✗ Branch 2 not taken.
 44 cache_.Insert(key, entry);
634 44 this->Unlock();
635 44 return true;
636 66 }
637
638
639 /**
640 * Retrieve an element from the cache.
641 * If the element was found, it will be marked as 'recently used' and returned
642 * @param key the key to perform a lookup on
643 * @param value (out) here the result is saved (not touch in case of miss)
644 * @return true on successful lookup, false if key was not found
645 */
646 341445 virtual bool Lookup(const Key &key, Value *value, bool update_lru = true) {
647 341445 bool found = false;
648 341445 Lock();
649
2/2
✓ Branch 0 taken 400 times.
✓ Branch 1 taken 340536 times.
 341445 if (pause_) {
650 400 Unlock();
651 400 return false;
652 }
653
654
1/2
✓ Branch 1 taken 295352 times.
✗ Branch 2 not taken.
 341045 CacheEntry entry;
655
3/4
✓ Branch 1 taken 340536 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 332993 times.
✓ Branch 4 taken 7543 times.
 341045 if (DoLookup(key, &entry)) {
656 // Hit
657 333204 perf::Inc(counters_.n_hit);
658
2/2
✓ Branch 0 taken 332327 times.
✓ Branch 1 taken 666 times.
 333204 if (update_lru)
659
1/2
✓ Branch 1 taken 332327 times.
✗ Branch 2 not taken.
 332538 Touch(entry);
660
1/2
✓ Branch 1 taken 44497 times.
✗ Branch 2 not taken.
 333204 *value = entry.value;
661 333204 found = true;
662 } else {
663 7841 perf::Inc(counters_.n_miss);
664 }
665
666 341045 Unlock();
667 341045 return found;
668 46202 }
669
670 /**
671 * Forgets about a specific cache entry
672 * @param key the key to delete from the cache
673 * @return true if key was deleted, false if key was not in the cache
674 */
675 596 virtual bool Forget(const Key &key) {
676 596 bool found = false;
677 596 this->Lock();
678
2/2
✓ Branch 0 taken 40 times.
✓ Branch 1 taken 556 times.
 596 if (pause_) {
679 40 Unlock();
680 40 return false;
681 }
682
683
1/2
✓ Branch 1 taken 196 times.
✗ Branch 2 not taken.
 556 CacheEntry entry;
684
3/4
✓ Branch 1 taken 556 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 416 times.
✓ Branch 4 taken 140 times.
 556 if (this->DoLookup(key, &entry)) {
685 416 found = true;
686 416 perf::Inc(counters_.n_forget);
687
688
1/2
✓ Branch 1 taken 416 times.
✗ Branch 2 not taken.
 416 entry.list_entry->RemoveFromList();
689
1/2
✓ Branch 1 taken 416 times.
✗ Branch 2 not taken.
 416 allocator_.Destruct(entry.list_entry);
690
1/2
✓ Branch 1 taken 416 times.
✗ Branch 2 not taken.
 416 cache_.Erase(key);
691 416 --cache_gauge_;
692 }
693
694 556 this->Unlock();
695 556 return found;
696 360 }
697
698 /**
699 * Clears all elements from the cache.
700 * All memory of internal data structures will be freed but data of
701 * cache entries may stay in use, we do not call delete on any user data.
702 */
703 42 virtual void Drop() {
704 42 this->Lock();
705
706 42 cache_gauge_ = 0;
707 42 lru_list_.clear();
708 42 cache_.Clear();
709 42 perf::Inc(counters_.n_drop);
710 42 counters_.sz_allocated->Set(0);
711 42 perf::Xadd(counters_.sz_allocated,
712 42 allocator_.bytes_allocated() + cache_.bytes_allocated());
713
714 42 this->Unlock();
715 42 }
716
717 121 void Pause() {
718 121 Lock();
719 121 pause_ = true;
720 121 Unlock();
721 121 }
722
723 60 void Resume() {
724 60 Lock();
725 60 pause_ = false;
726 60 Unlock();
727 60 }
728
729 202506 inline bool IsFull() const { return cache_gauge_ >= cache_size_; }
730 21206 inline bool IsEmpty() const { return cache_gauge_ == 0; }
731
732 Counters counters() {
733 Lock();
734 cache_.GetCollisionStats(&counters_.num_collisions,
735 &counters_.max_collisions);
736 Unlock();
737 return counters_;
738 }
739
740 /**
741 * Prepares for in-order iteration of the cache entries to perform a filter
742 * operation. To ensure consistency, the LruCache must be locked for the
743 * duration of the filter operation.
744 */
745 318 virtual void FilterBegin() {
746
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 318 times.
 318 assert(!filter_entry_);
747 318 Lock();
748 318 filter_entry_ = &lru_list_;
749 318 }
750
751 /**
752 * Get the current key and value for the filter operation
753 * @param key Address to write the key
754 * @param value Address to write the value
755 */
756 5234 virtual void FilterGet(Key *key, Value *value) {
757
1/2
✓ Branch 1 taken 5190 times.
✗ Branch 2 not taken.
 5234 CacheEntry entry;
758
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 5234 times.
 5234 assert(filter_entry_);
759
2/4
✓ Branch 1 taken 5234 times.
✗ Branch 2 not taken.
✗ Branch 3 not taken.
✓ Branch 4 taken 5234 times.
 5234 assert(!filter_entry_->IsListHead());
760 5234 *key = static_cast<ConcreteListEntryContent *>(filter_entry_)->content();
761
1/2
✓ Branch 1 taken 5234 times.
✗ Branch 2 not taken.
 5234 const bool rc = this->DoLookup(*key, &entry);
762
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 5234 times.
 5234 assert(rc);
763
1/2
✓ Branch 1 taken 44 times.
✗ Branch 2 not taken.
 5234 *value = entry.value;
764 5234 }
765
766 /**
767 * Advance to the next entry in the list
768 * @returns false upon reaching the end of the cache list
769 */
770 5508 virtual bool FilterNext() {
771
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 5508 times.
 5508 assert(filter_entry_);
772 5508 filter_entry_ = filter_entry_->next;
773 5508 return !filter_entry_->IsListHead();
774 }
775
776 /**
777 * Delete the current cache list entry
778 */
779 4916 virtual void FilterDelete() {
780
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 4916 times.
 4916 assert(filter_entry_);
781
2/4
✓ Branch 1 taken 4916 times.
✗ Branch 2 not taken.
✗ Branch 3 not taken.
✓ Branch 4 taken 4916 times.
 4916 assert(!filter_entry_->IsListHead());
782 4916 ListEntry<Key> *new_current = filter_entry_->prev;
783 4916 perf::Inc(counters_.n_forget);
784 4916 Key k = static_cast<ConcreteListEntryContent *>(filter_entry_)->content();
785
1/2
✓ Branch 1 taken 4916 times.
✗ Branch 2 not taken.
 4916 filter_entry_->RemoveFromList();
786
1/2
✓ Branch 1 taken 4916 times.
✗ Branch 2 not taken.
 4916 allocator_.Destruct(static_cast<ConcreteListEntryContent *>(filter_entry_));
787
1/2
✓ Branch 1 taken 4916 times.
✗ Branch 2 not taken.
 4916 cache_.Erase(k);
788 4916 --cache_gauge_;
789 4916 filter_entry_ = new_current;
790 4916 }
791
792 /**
793 * Finish filtering the entries and unlock the cache
794 */
795 318 virtual void FilterEnd() {
796
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 318 times.
 318 assert(filter_entry_);
797 318 filter_entry_ = NULL;
798 318 Unlock();
799 318 }
800
801 protected:
802 Counters counters_;
803
804 private:
805 /**
806 * this just performs a lookup in the cache
807 * WITHOUT changing the LRU order
808 * @param key the key to perform a lookup on
809 * @param entry a pointer to the entry structure
810 * @return true on successful lookup, false otherwise
811 */
812 727822 inline bool DoLookup(const Key &key, CacheEntry *entry) {
813 727822 return cache_.Lookup(key, entry);
814 }
815
816 /**
817 * Touch an entry.
818 * The entry will be moved to the back of the LRU list to mark it
819 * as 'recently used'... this saves the entry from being deleted
820 * @param entry the CacheEntry to be touched (CacheEntry is the internal
821 * wrapper data structure)
822 */
823 620201 inline void Touch(const CacheEntry &entry) {
824 620201 lru_list_.MoveToBack(entry.list_entry);
825 620201 }
826
827 /**
828 * Deletes the least recently used entry from the cache.
829 */
830 20382 inline void DeleteOldest() {
831
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 20382 times.
 20382 assert(!this->IsEmpty());
832
833 20382 perf::Inc(counters_.n_replace);
834
1/2
✓ Branch 1 taken 20382 times.
✗ Branch 2 not taken.
 20382 Key delete_me = lru_list_.PopFront();
835
1/2
✓ Branch 1 taken 20382 times.
✗ Branch 2 not taken.
 20382 cache_.Erase(delete_me);
836
837 20382 --cache_gauge_;
838 20382 }
839
840 /**
841 * Locks the cache (thread safety).
842 */
843 723609 inline void Lock() {
844 #ifdef LRU_CACHE_THREAD_SAFE
845 723609 pthread_mutex_lock(&lock_);
846 #endif
847 723609 }
848
849 /**
850 * Unlocks the cache (thread safety).
851 */
852 723609 inline void Unlock() {
853 #ifdef LRU_CACHE_THREAD_SAFE
854 723609 pthread_mutex_unlock(&lock_);
855 #endif
856 723609 }
857
858 bool pause_; /**< Temporarily stops the cache in order to avoid poisoning */
859
860 // Internal data fields
861 unsigned int cache_gauge_;
862 const unsigned int cache_size_;
863 ConcreteMemoryAllocator allocator_;
864
865 /**
866 * A doubly linked list to keep track of the least recently used data entries.
867 * New entries get pushed back to the list. If an entry is touched
868 * it is moved to the back of the list again.
869 * If the cache gets too long, the first element (the oldest) gets
870 * deleted to obtain some space.
871 */
872 ListEntryHead<Key> lru_list_;
873 SmallHashFixed<Key, CacheEntry> cache_;
874
875 ListEntry<Key> *filter_entry_;
876 #ifdef LRU_CACHE_THREAD_SAFE
877 pthread_mutex_t lock_; /**< Mutex to make cache thread safe. */
878 #endif
879 }; // class LruCache
880
881 } // namespace lru
882
883 #endif // CVMFS_LRU_H_
884