1 /*
2  * Copyright 2010 Marek Olšák <maraeo@gmail.com>
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a
5  * copy of this software and associated documentation files (the "Software"),
6  * to deal in the Software without restriction, including without limitation
7  * on the rights to use, copy, modify, merge, publish, distribute, sub
8  * license, and/or sell copies of the Software, and to permit persons to whom
9  * the Software is furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice (including the next
12  * paragraph) shall be included in all copies or substantial portions of the
13  * Software.
14  *
15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
18  * THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
19  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
20  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
21  * USE OR OTHER DEALINGS IN THE SOFTWARE. */
22 
23 /**
24  * @file
25  * Simple slab allocator for equally sized memory allocations.
26  * util_slab_alloc and util_slab_free have time complexity in O(1).
27  *
28  * Good for allocations which have very low lifetime and are allocated
29  * and freed very often. Use a profiler first to know if it's worth using it!
30  *
31  * Candidates: get_transfer
32  *
33  * @author Marek Olšák
34  */
35 
36 #ifndef U_SLAB_H
37 #define U_SLAB_H
38 
39 #include "os/os_thread.h"
40 
41 enum util_slab_threading {
42    UTIL_SLAB_SINGLETHREADED = FALSE,
43    UTIL_SLAB_MULTITHREADED = TRUE
44 };
45 
46 /* The page is an array of blocks (allocations). */
47 struct util_slab_page {
48    /* The header (linked-list pointers). */
49    struct util_slab_page *prev, *next;
50 
51    /* Memory after the last member is dedicated to the page itself.
52     * The allocated size is always larger than this structure. */
53 };
54 
55 struct util_slab_mempool {
56    /* Public members. */
57    void *(*alloc)(struct util_slab_mempool *pool);
58    void (*free)(struct util_slab_mempool *pool, void *ptr);
59 
60    /* Private members. */
61    struct util_slab_block *first_free;
62 
63    struct util_slab_page list;
64 
65    unsigned block_size;
66    unsigned page_size;
67    unsigned num_blocks;
68    unsigned num_pages;
69    enum util_slab_threading threading;
70 
71    pipe_mutex mutex;
72 };
73 
74 void util_slab_create(struct util_slab_mempool *pool,
75                       unsigned item_size,
76                       unsigned num_blocks,
77                       enum util_slab_threading threading);
78 
79 void util_slab_destroy(struct util_slab_mempool *pool);
80 
81 void util_slab_set_thread_safety(struct util_slab_mempool *pool,
82                                  enum util_slab_threading threading);
83 
84 #define util_slab_alloc(pool)     (pool)->alloc(pool)
85 #define util_slab_free(pool, ptr) (pool)->free(pool, ptr)
86 
87 #endif
88