src/util/slab.h

   1 /*
   2  * Copyright 2010 Marek Olšák <maraeo@gmail.com>
   3  * Copyright 2016 Advanced Micro Devices, Inc.
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a
   6  * copy of this software and associated documentation files (the "Software"),
   7  * to deal in the Software without restriction, including without limitation
   8  * on the rights to use, copy, modify, merge, publish, distribute, sub
   9  * license, and/or sell copies of the Software, and to permit persons to whom
  10  * the Software is furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice (including the next
  13  * paragraph) shall be included in all copies or substantial portions of the
  14  * Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
  20  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  21  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  22  * USE OR OTHER DEALINGS IN THE SOFTWARE. */
  23
  24 /**
  25  * Slab allocator for equally sized memory allocations.
  26  *
  27  * Objects are allocated from "child" pools that are connected to a "parent"
  28  * pool.
  29  *
  30  * Calls to slab_alloc/slab_free for the same child pool must not occur from
  31  * multiple threads simultaneously.
  32  *
  33  * Allocations obtained from one child pool should usually be freed in the
  34  * same child pool. Freeing an allocation in a different child pool associated
  35  * to the same parent is allowed (and requires no locking by the caller), but
  36  * it is discouraged because it implies a performance penalty.
  37  *
  38  * For convenience and to ease the transition, there is also a set of wrapper
  39  * functions around a single parent-child pair.
  40  */
  41
  42 #ifndef SLAB_H
  43 #define SLAB_H
  44
  45 #include "c11/threads.h"
  46
  47 struct slab_element_header;
  48 struct slab_page_header;
  49
  50 struct slab_parent_pool {
  51    mtx_t mutex;
  52    unsigned element_size;
  53    unsigned num_elements;
  54 };
  55
  56 struct slab_child_pool {
  57    struct slab_parent_pool *parent;
  58
  59    struct slab_page_header *pages;
  60
  61    /* Free elements. */
  62    struct slab_element_header *free;
  63
  64    /* Elements that are owned by this pool but were freed with a different
  65     * pool as the argument to slab_free.
  66     *
  67     * This list is protected by the parent mutex.
  68     */
  69    struct slab_element_header *migrated;
  70 };
  71
  72 void slab_create_parent(struct slab_parent_pool *parent,
  73                         unsigned item_size,
  74                         unsigned num_items);
  75 void slab_destroy_parent(struct slab_parent_pool *parent);
  76 void slab_create_child(struct slab_child_pool *pool,
  77                        struct slab_parent_pool *parent);
  78 void slab_destroy_child(struct slab_child_pool *pool);
  79 void *slab_alloc(struct slab_child_pool *pool);
  80 void slab_free(struct slab_child_pool *pool, void *ptr);
  81
  82 struct slab_mempool {
  83    struct slab_parent_pool parent;
  84    struct slab_child_pool child;
  85 };
  86
  87 void slab_create(struct slab_mempool *mempool,
  88                  unsigned item_size,
  89                  unsigned num_items);
  90 void slab_destroy(struct slab_mempool *mempool);
  91 void *slab_alloc_st(struct slab_mempool *mempool);
  92 void slab_free_st(struct slab_mempool *mempool, void *ptr);
  93
  94 #endif