xref: /freebsd/usr.sbin/nscd/cacheplcs.c (revision 734e82fe33aa764367791a7d603b383996c6b40b)
1 /*-
2  * Copyright (c) 2005 Michael Bushkov <bushman@rsu.ru>
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  *
26  */
27 
28 #include <sys/cdefs.h>
29 #include <sys/time.h>
30 
31 #include <assert.h>
32 #include <stdlib.h>
33 #include <string.h>
34 
35 #include "cacheplcs.h"
36 #include "debug.h"
37 
38 static void cache_fifo_policy_update_item(struct cache_policy_ *,
39 	struct cache_policy_item_ *);
40 static void cache_lfu_policy_add_item(struct cache_policy_ *,
41 	struct cache_policy_item_ *);
42 static struct cache_policy_item_ * cache_lfu_policy_create_item(void);
43 static void cache_lfu_policy_destroy_item(struct cache_policy_item_ *);
44 static struct cache_policy_item_ *cache_lfu_policy_get_first_item(
45 	struct cache_policy_ *);
46 static struct cache_policy_item_ *cache_lfu_policy_get_last_item(
47 	struct cache_policy_ *);
48 static struct cache_policy_item_ *cache_lfu_policy_get_next_item(
49 	struct cache_policy_ *, struct cache_policy_item_ *);
50 static struct cache_policy_item_ *cache_lfu_policy_get_prev_item(
51 	struct cache_policy_ *, struct cache_policy_item_ *);
52 static void cache_lfu_policy_remove_item(struct cache_policy_ *,
53 	struct cache_policy_item_ *);
54 static void cache_lfu_policy_update_item(struct cache_policy_ *,
55 	struct cache_policy_item_ *);
56 static void cache_lru_policy_update_item(struct cache_policy_ *,
57 	struct cache_policy_item_ *);
58 static void cache_queue_policy_add_item(struct cache_policy_ *,
59 	struct cache_policy_item_ *);
60 static struct cache_policy_item_ * cache_queue_policy_create_item(void);
61 static void cache_queue_policy_destroy_item(struct cache_policy_item_ *);
62 static struct cache_policy_item_ *cache_queue_policy_get_first_item(
63 	struct cache_policy_ *);
64 static struct cache_policy_item_ *cache_queue_policy_get_last_item(
65 	struct cache_policy_ *);
66 static struct cache_policy_item_ *cache_queue_policy_get_next_item(
67 	struct cache_policy_ *, struct cache_policy_item_ *);
68 static struct cache_policy_item_ *cache_queue_policy_get_prev_item(
69 	struct cache_policy_ *, struct cache_policy_item_ *);
70 static void cache_queue_policy_remove_item(struct cache_policy_ *,
71 	struct cache_policy_item_ *);
72 static void destroy_cache_queue_policy(struct cache_queue_policy_ *);
73 static struct cache_queue_policy_ *init_cache_queue_policy(void);
74 
75 /*
76  * All cache_queue_policy_XXX functions below will be used to fill
77  * the cache_queue_policy structure. They implement the most functionality of
78  * LRU and FIFO policies. LRU and FIFO policies are actually the
79  * cache_queue_policy_ with cache_update_item function changed.
80  */
81 static struct cache_policy_item_ *
82 cache_queue_policy_create_item(void)
83 {
84 	struct cache_queue_policy_item_ *retval;
85 
86 	TRACE_IN(cache_queue_policy_create_item);
87 	retval = calloc(1,
88 		sizeof(*retval));
89 	assert(retval != NULL);
90 
91 	TRACE_OUT(cache_queue_policy_create_item);
92 	return ((struct cache_policy_item_ *)retval);
93 }
94 
95 static void
96 cache_queue_policy_destroy_item(struct cache_policy_item_ *item)
97 {
98 
99 	TRACE_IN(cache_queue_policy_destroy_item);
100 	assert(item != NULL);
101 	free(item);
102 	TRACE_OUT(cache_queue_policy_destroy_item);
103 }
104 
105 static void
106 cache_queue_policy_add_item(struct cache_policy_ *policy,
107 	struct cache_policy_item_ *item)
108 {
109 	struct cache_queue_policy_ *queue_policy;
110 	struct cache_queue_policy_item_ *queue_item;
111 
112 	TRACE_IN(cache_queue_policy_add_item);
113 	queue_policy = (struct cache_queue_policy_ *)policy;
114 	queue_item = (struct cache_queue_policy_item_ *)item;
115 	TAILQ_INSERT_TAIL(&queue_policy->head, queue_item, entries);
116 	TRACE_OUT(cache_queue_policy_add_item);
117 }
118 
119 static void
120 cache_queue_policy_remove_item(struct cache_policy_ *policy,
121 	struct cache_policy_item_ *item)
122 {
123 	struct cache_queue_policy_ *queue_policy;
124 	struct cache_queue_policy_item_	*queue_item;
125 
126 	TRACE_IN(cache_queue_policy_remove_item);
127 	queue_policy = (struct cache_queue_policy_ *)policy;
128 	queue_item = (struct cache_queue_policy_item_ *)item;
129 	TAILQ_REMOVE(&queue_policy->head, queue_item, entries);
130 	TRACE_OUT(cache_queue_policy_remove_item);
131 }
132 
133 static struct cache_policy_item_ *
134 cache_queue_policy_get_first_item(struct cache_policy_ *policy)
135 {
136 	struct cache_queue_policy_ *queue_policy;
137 
138 	TRACE_IN(cache_queue_policy_get_first_item);
139 	queue_policy = (struct cache_queue_policy_ *)policy;
140 	TRACE_OUT(cache_queue_policy_get_first_item);
141 	return ((struct cache_policy_item_ *)TAILQ_FIRST(&queue_policy->head));
142 }
143 
144 static struct cache_policy_item_ *
145 cache_queue_policy_get_last_item(struct cache_policy_ *policy)
146 {
147 	struct cache_queue_policy_ *queue_policy;
148 
149 	TRACE_IN(cache_queue_policy_get_last_item);
150 	queue_policy = (struct cache_queue_policy_ *)policy;
151 	TRACE_OUT(cache_queue_policy_get_last_item);
152 	return ((struct cache_policy_item_ *)TAILQ_LAST(&queue_policy->head,
153 		cache_queue_policy_head_));
154 }
155 
156 static struct cache_policy_item_ *
157 cache_queue_policy_get_next_item(struct cache_policy_ *policy,
158 	struct cache_policy_item_ *item)
159 {
160 	struct cache_queue_policy_item_	*queue_item;
161 
162 	TRACE_IN(cache_queue_policy_get_next_item);
163 	queue_item = (struct cache_queue_policy_item_ *)item;
164 
165 	TRACE_OUT(cache_queue_policy_get_next_item);
166 	return ((struct cache_policy_item_ *)TAILQ_NEXT(queue_item, entries));
167 }
168 
169 static struct cache_policy_item_ *
170 cache_queue_policy_get_prev_item(struct cache_policy_ *policy,
171 	struct cache_policy_item_ *item)
172 {
173 	struct cache_queue_policy_item_	*queue_item;
174 
175 	TRACE_IN(cache_queue_policy_get_prev_item);
176 	queue_item = (struct cache_queue_policy_item_ *)item;
177 
178 	TRACE_OUT(cache_queue_policy_get_prev_item);
179 	return ((struct cache_policy_item_ *)TAILQ_PREV(queue_item,
180 		cache_queue_policy_head_, entries));
181 }
182 
183 /*
184  * Initializes cache_queue_policy_ by filling the structure with the functions
185  * pointers, defined above
186  */
187 static struct cache_queue_policy_ *
188 init_cache_queue_policy(void)
189 {
190 	struct cache_queue_policy_	*retval;
191 
192 	TRACE_IN(init_cache_queue_policy);
193 	retval = calloc(1,
194 		sizeof(*retval));
195 	assert(retval != NULL);
196 
197 	retval->parent_data.create_item_func = cache_queue_policy_create_item;
198 	retval->parent_data.destroy_item_func = cache_queue_policy_destroy_item;
199 
200 	retval->parent_data.add_item_func = cache_queue_policy_add_item;
201 	retval->parent_data.remove_item_func = cache_queue_policy_remove_item;
202 
203 	retval->parent_data.get_first_item_func =
204 		cache_queue_policy_get_first_item;
205 	retval->parent_data.get_last_item_func =
206 		cache_queue_policy_get_last_item;
207 	retval->parent_data.get_next_item_func =
208 		cache_queue_policy_get_next_item;
209 	retval->parent_data.get_prev_item_func =
210 		cache_queue_policy_get_prev_item;
211 
212 	TAILQ_INIT(&retval->head);
213 	TRACE_OUT(init_cache_queue_policy);
214 	return (retval);
215 }
216 
217 static void
218 destroy_cache_queue_policy(struct cache_queue_policy_ *queue_policy)
219 {
220 	struct cache_queue_policy_item_	*queue_item;
221 
222 	TRACE_IN(destroy_cache_queue_policy);
223 	while (!TAILQ_EMPTY(&queue_policy->head)) {
224 		queue_item = TAILQ_FIRST(&queue_policy->head);
225 		TAILQ_REMOVE(&queue_policy->head, queue_item, entries);
226 		cache_queue_policy_destroy_item(
227 			(struct cache_policy_item_ *)queue_item);
228 	}
229 	free(queue_policy);
230 	TRACE_OUT(destroy_cache_queue_policy);
231 }
232 
233 /*
234  * Makes cache_queue_policy_ behave like FIFO policy - we don't do anything,
235  * when the cache element is updated. So it always stays in its initial
236  * position in the queue - that is exactly the FIFO functionality.
237  */
238 static void
239 cache_fifo_policy_update_item(struct cache_policy_ *policy,
240 	struct cache_policy_item_ *item)
241 {
242 
243 	TRACE_IN(cache_fifo_policy_update_item);
244 	/* policy and item arguments are ignored */
245 	TRACE_OUT(cache_fifo_policy_update_item);
246 }
247 
248 struct cache_policy_ *
249 init_cache_fifo_policy(void)
250 {
251 	struct cache_queue_policy_ *retval;
252 
253 	TRACE_IN(init_cache_fifo_policy);
254 	retval = init_cache_queue_policy();
255 	retval->parent_data.update_item_func = cache_fifo_policy_update_item;
256 
257 	TRACE_OUT(init_cache_fifo_policy);
258 	return ((struct cache_policy_ *)retval);
259 }
260 
261 void
262 destroy_cache_fifo_policy(struct cache_policy_ *policy)
263 {
264 	struct cache_queue_policy_	*queue_policy;
265 
266 	TRACE_IN(destroy_cache_fifo_policy);
267 	queue_policy = (struct cache_queue_policy_ *)policy;
268 	destroy_cache_queue_policy(queue_policy);
269 	TRACE_OUT(destroy_cache_fifo_policy);
270 }
271 
272 /*
273  * Makes cache_queue_policy_ behave like LRU policy. On each update, cache
274  * element is moved to the end of the queue - so it would be deleted in last
275  * turn. That is exactly the LRU policy functionality.
276  */
277 static void
278 cache_lru_policy_update_item(struct cache_policy_ *policy,
279 	struct cache_policy_item_ *item)
280 {
281 	struct cache_queue_policy_ *queue_policy;
282 	struct cache_queue_policy_item_ *queue_item;
283 
284 	TRACE_IN(cache_lru_policy_update_item);
285 	queue_policy = (struct cache_queue_policy_ *)policy;
286 	queue_item = (struct cache_queue_policy_item_ *)item;
287 
288 	TAILQ_REMOVE(&queue_policy->head, queue_item, entries);
289 	TAILQ_INSERT_TAIL(&queue_policy->head, queue_item, entries);
290 	TRACE_OUT(cache_lru_policy_update_item);
291 }
292 
293 struct cache_policy_ *
294 init_cache_lru_policy(void)
295 {
296 	struct cache_queue_policy_ *retval;
297 
298 	TRACE_IN(init_cache_lru_policy);
299 	retval = init_cache_queue_policy();
300 	retval->parent_data.update_item_func = cache_lru_policy_update_item;
301 
302 	TRACE_OUT(init_cache_lru_policy);
303 	return ((struct cache_policy_ *)retval);
304 }
305 
306 void
307 destroy_cache_lru_policy(struct cache_policy_ *policy)
308 {
309 	struct cache_queue_policy_	*queue_policy;
310 
311 	TRACE_IN(destroy_cache_lru_policy);
312 	queue_policy = (struct cache_queue_policy_ *)policy;
313 	destroy_cache_queue_policy(queue_policy);
314 	TRACE_OUT(destroy_cache_lru_policy);
315 }
316 
317 /*
318  * LFU (least frequently used) policy implementation differs much from the
319  * LRU and FIFO (both based on cache_queue_policy_). Almost all cache_policy_
320  * functions are implemented specifically for this policy. The idea of this
321  * policy is to represent frequency (real number) as the integer number and
322  * use it as the index in the array. Each array's element is
323  * the list of elements. For example, if we have the 100-elements
324  * array for this policy, the elements with frequency 0.1 (calls per-second)
325  * would be in 10th element of the array.
326  */
327 static struct cache_policy_item_ *
328 cache_lfu_policy_create_item(void)
329 {
330 	struct cache_lfu_policy_item_ *retval;
331 
332 	TRACE_IN(cache_lfu_policy_create_item);
333 	retval = calloc(1,
334 		sizeof(*retval));
335 	assert(retval != NULL);
336 
337 	TRACE_OUT(cache_lfu_policy_create_item);
338 	return ((struct cache_policy_item_ *)retval);
339 }
340 
341 static void
342 cache_lfu_policy_destroy_item(struct cache_policy_item_ *item)
343 {
344 
345 	TRACE_IN(cache_lfu_policy_destroy_item);
346 	assert(item != NULL);
347 	free(item);
348 	TRACE_OUT(cache_lfu_policy_destroy_item);
349 }
350 
351 /*
352  * When placed in the LFU policy queue for the first time, the maximum
353  * frequency is assigned to the element
354  */
355 static void
356 cache_lfu_policy_add_item(struct cache_policy_ *policy,
357 	struct cache_policy_item_ *item)
358 {
359 	struct cache_lfu_policy_ *lfu_policy;
360 	struct cache_lfu_policy_item_ *lfu_item;
361 
362 	TRACE_IN(cache_lfu_policy_add_item);
363 	lfu_policy = (struct cache_lfu_policy_ *)policy;
364 	lfu_item = (struct cache_lfu_policy_item_ *)item;
365 
366 	lfu_item->frequency = CACHELIB_MAX_FREQUENCY - 1;
367 	TAILQ_INSERT_HEAD(&(lfu_policy->groups[CACHELIB_MAX_FREQUENCY - 1]),
368 		lfu_item, entries);
369 	TRACE_OUT(cache_lfu_policy_add_item);
370 }
371 
372 /*
373  * On each update the frequency of the element is recalculated and, if it
374  * changed, the element would be moved to the another place in the array.
375  */
376 static void
377 cache_lfu_policy_update_item(struct cache_policy_ *policy,
378 	struct cache_policy_item_ *item)
379 {
380 	struct cache_lfu_policy_ *lfu_policy;
381 	struct cache_lfu_policy_item_ *lfu_item;
382 	int index;
383 
384 	TRACE_IN(cache_lfu_policy_update_item);
385 	lfu_policy = (struct cache_lfu_policy_ *)policy;
386 	lfu_item = (struct cache_lfu_policy_item_ *)item;
387 
388 	/*
389 	 * We calculate the square of the request_count to avoid grouping of
390 	 * all elements at the start of the array (for example, if array size is
391 	 * 100 and most of its elements has frequency below the 0.01, they
392 	 * all would be grouped in the first array's position). Other
393 	 * techniques should be used here later to ensure, that elements are
394 	 * equally distributed  in the array and not grouped in its beginning.
395 	 */
396 	if (lfu_item->parent_data.last_request_time.tv_sec !=
397 		lfu_item->parent_data.creation_time.tv_sec) {
398 		index = ((double)lfu_item->parent_data.request_count *
399 			(double)lfu_item->parent_data.request_count /
400 			(lfu_item->parent_data.last_request_time.tv_sec -
401 			    lfu_item->parent_data.creation_time.tv_sec + 1)) *
402 			    CACHELIB_MAX_FREQUENCY;
403 		if (index >= CACHELIB_MAX_FREQUENCY)
404 			index = CACHELIB_MAX_FREQUENCY - 1;
405 	} else
406 		index = CACHELIB_MAX_FREQUENCY - 1;
407 
408 	TAILQ_REMOVE(&(lfu_policy->groups[lfu_item->frequency]), lfu_item,
409 		entries);
410 	lfu_item->frequency = index;
411 	TAILQ_INSERT_HEAD(&(lfu_policy->groups[index]), lfu_item, entries);
412 
413 	TRACE_OUT(cache_lfu_policy_update_item);
414 }
415 
416 static void
417 cache_lfu_policy_remove_item(struct cache_policy_ *policy,
418 	struct cache_policy_item_ *item)
419 {
420 	struct cache_lfu_policy_ *lfu_policy;
421 	struct cache_lfu_policy_item_ *lfu_item;
422 
423 	TRACE_IN(cache_lfu_policy_remove_item);
424 	lfu_policy = (struct cache_lfu_policy_ *)policy;
425 	lfu_item = (struct cache_lfu_policy_item_ *)item;
426 
427 	TAILQ_REMOVE(&(lfu_policy->groups[lfu_item->frequency]), lfu_item,
428 		entries);
429 	TRACE_OUT(cache_lfu_policy_remove_item);
430 }
431 
432 static struct cache_policy_item_ *
433 cache_lfu_policy_get_first_item(struct cache_policy_ *policy)
434 {
435 	struct cache_lfu_policy_ *lfu_policy;
436 	struct cache_lfu_policy_item_ *lfu_item;
437 	int i;
438 
439 	TRACE_IN(cache_lfu_policy_get_first_item);
440 	lfu_item = NULL;
441 	lfu_policy = (struct cache_lfu_policy_ *)policy;
442 	for (i = 0; i < CACHELIB_MAX_FREQUENCY; ++i)
443 		if (!TAILQ_EMPTY(&(lfu_policy->groups[i]))) {
444 			lfu_item = TAILQ_FIRST(&(lfu_policy->groups[i]));
445 			break;
446 		}
447 
448 	TRACE_OUT(cache_lfu_policy_get_first_item);
449 	return ((struct cache_policy_item_ *)lfu_item);
450 }
451 
452 static struct cache_policy_item_ *
453 cache_lfu_policy_get_last_item(struct cache_policy_ *policy)
454 {
455 	struct cache_lfu_policy_ *lfu_policy;
456 	struct cache_lfu_policy_item_ *lfu_item;
457 	int i;
458 
459 	TRACE_IN(cache_lfu_policy_get_last_item);
460 	lfu_item = NULL;
461 	lfu_policy = (struct cache_lfu_policy_ *)policy;
462 	for (i = CACHELIB_MAX_FREQUENCY - 1; i >= 0; --i)
463 		if (!TAILQ_EMPTY(&(lfu_policy->groups[i]))) {
464 			lfu_item = TAILQ_LAST(&(lfu_policy->groups[i]),
465 				cache_lfu_policy_group_);
466 			break;
467 		}
468 
469 	TRACE_OUT(cache_lfu_policy_get_last_item);
470 	return ((struct cache_policy_item_ *)lfu_item);
471 }
472 
473 static struct cache_policy_item_ *
474 cache_lfu_policy_get_next_item(struct cache_policy_ *policy,
475 	struct cache_policy_item_ *item)
476 {
477 	struct cache_lfu_policy_ *lfu_policy;
478 	struct cache_lfu_policy_item_ *lfu_item;
479 	int i;
480 
481 	TRACE_IN(cache_lfu_policy_get_next_item);
482 	lfu_policy = (struct cache_lfu_policy_ *)policy;
483 	lfu_item = TAILQ_NEXT((struct cache_lfu_policy_item_ *)item, entries);
484 	if (lfu_item == NULL)
485 	{
486 		for (i = ((struct cache_lfu_policy_item_ *)item)->frequency + 1;
487 			i < CACHELIB_MAX_FREQUENCY; ++i) {
488 			if (!TAILQ_EMPTY(&(lfu_policy->groups[i]))) {
489 			    lfu_item = TAILQ_FIRST(&(lfu_policy->groups[i]));
490 			    break;
491 			}
492 		}
493 	}
494 
495 	TRACE_OUT(cache_lfu_policy_get_next_item);
496 	return ((struct cache_policy_item_ *)lfu_item);
497 }
498 
499 static struct cache_policy_item_ *
500 cache_lfu_policy_get_prev_item(struct cache_policy_ *policy,
501 	struct cache_policy_item_ *item)
502 {
503 	struct cache_lfu_policy_ *lfu_policy;
504 	struct cache_lfu_policy_item_ *lfu_item;
505 	int i;
506 
507 	TRACE_IN(cache_lfu_policy_get_prev_item);
508 	lfu_policy = (struct cache_lfu_policy_ *)policy;
509 	lfu_item = TAILQ_PREV((struct cache_lfu_policy_item_ *)item,
510 		cache_lfu_policy_group_, entries);
511 	if (lfu_item == NULL)
512 	{
513 		for (i = ((struct cache_lfu_policy_item_ *)item)->frequency - 1;
514 			i >= 0; --i)
515 			if (!TAILQ_EMPTY(&(lfu_policy->groups[i]))) {
516 				lfu_item = TAILQ_LAST(&(lfu_policy->groups[i]),
517 					cache_lfu_policy_group_);
518 				break;
519 		}
520 	}
521 
522 	TRACE_OUT(cache_lfu_policy_get_prev_item);
523 	return ((struct cache_policy_item_ *)lfu_item);
524 }
525 
526 /*
527  * Initializes the cache_policy_ structure by filling it with appropriate
528  * functions pointers
529  */
530 struct cache_policy_ *
531 init_cache_lfu_policy(void)
532 {
533 	int i;
534 	struct cache_lfu_policy_ *retval;
535 
536 	TRACE_IN(init_cache_lfu_policy);
537 	retval = calloc(1,
538 		sizeof(*retval));
539 	assert(retval != NULL);
540 
541 	retval->parent_data.create_item_func = cache_lfu_policy_create_item;
542 	retval->parent_data.destroy_item_func = cache_lfu_policy_destroy_item;
543 
544 	retval->parent_data.add_item_func = cache_lfu_policy_add_item;
545 	retval->parent_data.update_item_func = cache_lfu_policy_update_item;
546 	retval->parent_data.remove_item_func = cache_lfu_policy_remove_item;
547 
548 	retval->parent_data.get_first_item_func =
549 		cache_lfu_policy_get_first_item;
550 	retval->parent_data.get_last_item_func =
551 		cache_lfu_policy_get_last_item;
552 	retval->parent_data.get_next_item_func =
553 		cache_lfu_policy_get_next_item;
554 	retval->parent_data.get_prev_item_func =
555 		cache_lfu_policy_get_prev_item;
556 
557 	for (i = 0; i < CACHELIB_MAX_FREQUENCY; ++i)
558 		TAILQ_INIT(&(retval->groups[i]));
559 
560 	TRACE_OUT(init_cache_lfu_policy);
561 	return ((struct cache_policy_ *)retval);
562 }
563 
564 void
565 destroy_cache_lfu_policy(struct cache_policy_ *policy)
566 {
567 	int i;
568 	struct cache_lfu_policy_ *lfu_policy;
569 	struct cache_lfu_policy_item_ *lfu_item;
570 
571 	TRACE_IN(destroy_cache_lfu_policy);
572 	lfu_policy = (struct cache_lfu_policy_ *)policy;
573 	for (i = 0; i < CACHELIB_MAX_FREQUENCY; ++i) {
574 		while (!TAILQ_EMPTY(&(lfu_policy->groups[i]))) {
575 			lfu_item = TAILQ_FIRST(&(lfu_policy->groups[i]));
576 			TAILQ_REMOVE(&(lfu_policy->groups[i]), lfu_item,
577 				entries);
578 			cache_lfu_policy_destroy_item(
579 				(struct cache_policy_item_ *)lfu_item);
580 		}
581 	}
582 	free(policy);
583 	TRACE_OUT(destroy_cache_lfu_policy);
584 }
585