/*
* Copyright (C) Igor Sysoev
* Copyright (C) NGINX, Inc.
*/
#include <nxt_main.h>
/*
* A memory cache pool allocates memory in clusters of specified size and
* aligned to page_alignment. A cluster is divided on pages of specified
* size. Page size must be a power of 2. A page can be used entirely or
* can be divided on chunks of equal size. Chunk size must be a power of 2.
* A cluster can contains pages with different chunk sizes. Cluster size
* must be multiple of page size and may be not a power of 2. Allocations
* greater than page are allocated outside clusters. Start addresses and
* sizes of clusters and large allocations are stored in rbtree to find
* them on free operations. The rbtree nodes are sorted by start addresses.
*/
typedef struct nxt_mem_cache_page_s nxt_mem_cache_page_t;
struct nxt_mem_cache_page_s {
/* Chunk bitmap. There can be no more than 32 chunks in a page. */
uint8_t map[4];
/* Number of free chunks of a chunked page. */
uint8_t chunks;
/*
* Size of chunks or page shifted by pool->chunk_size_shift.
* Zero means that page is free.
*/
uint8_t size;
/*
* Page number in page cluster.
* There can be no more than 65536 pages in a cluster.
*/
uint16_t number;
/*
* Used to link pages with free chunks in pool chunk slot list
* or to link free pages in clusters.
*/
nxt_queue_link_t link;
};
typedef struct {
NXT_RBTREE_NODE (node);
uint8_t type;
uint32_t size;
u_char *start;
nxt_mem_cache_page_t pages[];
} nxt_mem_cache_block_t;
typedef struct {
nxt_queue_t pages;
#if (NXT_64BIT)
uint32_t size;
uint32_t chunks;
#else
uint16_t size;
uint16_t chunks;
#endif
} nxt_mem_cache_slot_t;
struct nxt_mem_cache_pool_s {
/* rbtree of nxt_mem_cache_block_t. */
nxt_rbtree_t pages;
nxt_queue_t free_pages;
uint8_t chunk_size_shift;
uint8_t page_size_shift;
uint32_t page_size;
uint32_t page_alignment;
uint32_t cluster_size;
nxt_mem_cache_slot_t slots[];
};
/* A cluster cache block. */
#define NXT_MEM_CACHE_CLUSTER_BLOCK 0
/* A discrete cache block of large allocation. */
#define NXT_MEM_CACHE_DISCRETE_BLOCK 1
/*
* An embedded cache block allocated together with large allocation
* just after the allocation.
*/
#define NXT_MEM_CACHE_EMBEDDED_BLOCK 2
#define \
nxt_mem_cache_chunk_is_free(map, chunk) \
((map[chunk / 8] & (0x80 >> (chunk & 7))) == 0)
#define \
nxt_mem_cache_chunk_set_free(map, chunk) \
map[chunk / 8] &= ~(0x80 >> (chunk & 7))
#define \
nxt_mem_cache_free_junk(p, size) \
nxt_memset((p), 0x5A, size)
static nxt_uint_t nxt_mem_cache_shift(nxt_uint_t n);
static void *nxt_mem_cache_alloc_small(nxt_mem_cache_pool_t *pool, size_t size);
static nxt_uint_t nxt_mem_cache_alloc_chunk(u_char *map, nxt_uint_t size);
static nxt_mem_cache_page_t *
nxt_mem_cache_alloc_page(nxt_mem_cache_pool_t *pool);
static nxt_mem_cache_block_t *
nxt_mem_cache_alloc_cluster(nxt_mem_cache_pool_t *pool);
static void *nxt_mem_cache_alloc_large(nxt_mem_cache_pool_t *pool,
size_t alignment, size_t size);
static intptr_t nxt_mem_cache_rbtree_compare(nxt_rbtree_node_t *node1,
nxt_rbtree_node_t *node2);
static nxt_mem_cache_block_t *nxt_mem_cache_find_block(nxt_rbtree_t *tree,
u_char *p);
static const char *nxt_mem_cache_chunk_free(nxt_mem_cache_pool_t *pool,
nxt_mem_cache_block_t *cluster, u_char *p);
nxt_mem_cache_pool_t *
nxt_mem_cache_pool_create(size_t cluster_size, size_t page_alignment,
size_t page_size, size_t min_chunk_size)
{
/* Alignment and sizes must be a power of 2. */
if (nxt_slow_path((page_alignment & (page_alignment - 1)) != 0
|| (page_size & (page_size - 1)) != 0
|| (min_chunk_size & (min_chunk_size - 1)) != 0))
{
return NULL;
}
page_alignment = nxt_max(page_alignment, NXT_MAX_ALIGNMENT);
if (nxt_slow_path(page_size < 64
|| page_size < page_alignment
|| page_size < min_chunk_size
|| min_chunk_size * 32 < page_size
|| cluster_size < page_size
|| cluster_size % page_size != 0))
{
return NULL;
}
return nxt_mem_cache_pool_fast_create(cluster_size, page_alignment,
page_size, min_chunk_size);
}
nxt_mem_cache_pool_t *
nxt_mem_cache_pool_fast_create(size_t cluster_size, size_t page_alignment,
size_t page_size, size_t min_chunk_size)
{
nxt_uint_t slots, chunk_size;
nxt_mem_cache_slot_t *slot;
nxt_mem_cache_pool_t *pool;
slots = 0;
chunk_size = page_size;
do {
slots++;
chunk_size /= 2;
} while (chunk_size > min_chunk_size);
pool = nxt_zalloc(sizeof(nxt_mem_cache_pool_t)
+ slots * sizeof(nxt_mem_cache_slot_t));
if (nxt_fast_path(pool != NULL)) {
pool->page_size = page_size;
pool->page_alignment = nxt_max(page_alignment, NXT_MAX_ALIGNMENT);
pool->cluster_size = cluster_size;
slot = pool->slots;
do {
nxt_queue_init(&slot->pages);
slot->size = chunk_size;
/* slot->chunks should be one less than actual number of chunks. */
slot->chunks = (page_size / chunk_size) - 1;
slot++;
chunk_size *= 2;
} while (chunk_size < page_size);
pool->chunk_size_shift = nxt_mem_cache_shift(min_chunk_size);
pool->page_size_shift = nxt_mem_cache_shift(page_size);
nxt_rbtree_init(&pool->pages, nxt_mem_cache_rbtree_compare);
nxt_queue_init(&pool->free_pages);
}
return pool;
}
static nxt_uint_t
nxt_mem_cache_shift(nxt_uint_t n)
{
nxt_uint_t shift;
shift = 0;
n /= 2;
do {
shift++;
n /= 2;
} while (n != 0);
return shift;
}
nxt_bool_t
nxt_mem_cache_pool_is_empty(nxt_mem_cache_pool_t *pool)
{
return (nxt_rbtree_is_empty(&pool->pages)
&& nxt_queue_is_empty(&pool->free_pages));
}
void
nxt_mem_cache_pool_destroy(nxt_mem_cache_pool_t *pool)
{
void *p;
nxt_rbtree_node_t *node, *next;
nxt_mem_cache_block_t *block;
for (node = nxt_rbtree_min(&pool->pages);
nxt_rbtree_is_there_successor(&pool->pages, node);
node = next)
{
next = nxt_rbtree_node_successor(&pool->pages, node);
block = (nxt_mem_cache_block_t *) node;
nxt_rbtree_delete(&pool->pages, &block->node);
p = block->start;
if (block->type != NXT_MEM_CACHE_EMBEDDED_BLOCK) {
nxt_free(block);
}
nxt_free(p);
}
nxt_free(pool);
}
nxt_inline u_char *
nxt_mem_cache_page_addr(nxt_mem_cache_pool_t *pool, nxt_mem_cache_page_t *page)
{
nxt_mem_cache_block_t *block;
block = (nxt_mem_cache_block_t *)
((u_char *) page - page->number * sizeof(nxt_mem_cache_page_t)
- offsetof(nxt_mem_cache_block_t, pages));
return block->start + (page->number << pool->page_size_shift);
}
void *
nxt_mem_cache_alloc(nxt_mem_cache_pool_t *pool, size_t size)
{
nxt_thread_log_debug("mem cache alloc: %uz", size);
if (size <= pool->page_size) {
return nxt_mem_cache_alloc_small(pool, size);
}
return nxt_mem_cache_alloc_large(pool, NXT_MAX_ALIGNMENT, size);
}
void *
nxt_mem_cache_zalloc(nxt_mem_cache_pool_t *pool, size_t size)
{
void *p;
p = nxt_mem_cache_alloc(pool, size);
if (nxt_fast_path(p != NULL)) {
nxt_memzero(p, size);
}
return p;
}
void *
nxt_mem_cache_align(nxt_mem_cache_pool_t *pool, size_t alignment, size_t size)
{
nxt_thread_log_debug("mem cache align: @%uz:%uz", alignment, size);
/* Alignment must be a power of 2. */
if (nxt_fast_path((alignment - 1) & alignment) == 0) {
if (size <= pool->page_size && alignment <= pool->page_alignment) {
size = nxt_max(size, alignment);
if (size <= pool->page_size) {
return nxt_mem_cache_alloc_small(pool, size);
}
}
return nxt_mem_cache_alloc_large(pool, alignment, size);
}
return NULL;
}
void *
nxt_mem_cache_zalign(nxt_mem_cache_pool_t *pool, size_t alignment, size_t size)
{
void *p;
p = nxt_mem_cache_align(pool, alignment, size);
if (nxt_fast_path(p != NULL)) {
nxt_memzero(p, size);
}
return p;
}
static void *
nxt_mem_cache_alloc_small(nxt_mem_cache_pool_t *pool, size_t size)
{
u_char *p;
nxt_queue_link_t *link;
nxt_mem_cache_page_t *page;
nxt_mem_cache_slot_t *slot;
p = NULL;
if (size <= pool->page_size / 2) {
/* Find a slot with appropriate chunk size. */
for (slot = pool->slots; slot->size < size; slot++) { /* void */ }
size = slot->size;
if (nxt_fast_path(!nxt_queue_is_empty(&slot->pages))) {
link = nxt_queue_first(&slot->pages);
page = nxt_queue_link_data(link, nxt_mem_cache_page_t, link);
p = nxt_mem_cache_page_addr(pool, page);
p += nxt_mem_cache_alloc_chunk(page->map, size);
page->chunks--;
if (page->chunks == 0) {
/*
* Remove full page from the pool chunk slot list
* of pages with free chunks.
*/
nxt_queue_remove(&page->link);
}
} else {
page = nxt_mem_cache_alloc_page(pool);
if (nxt_fast_path(page != NULL)) {
nxt_queue_insert_head(&slot->pages, &page->link);
/* Mark the first chunk as busy. */
page->map[0] = 0x80;
page->map[1] = 0;
page->map[2] = 0;
page->map[3] = 0;
/* slot->chunks are already one less. */
page->chunks = slot->chunks;
page->size = size >> pool->chunk_size_shift;
p = nxt_mem_cache_page_addr(pool, page);
}
}
} else {
page = nxt_mem_cache_alloc_page(pool);
if (nxt_fast_path(page != NULL)) {
page->size = pool->page_size >> pool->chunk_size_shift;
p = nxt_mem_cache_page_addr(pool, page);
}
#if (NXT_DEBUG)
size = pool->page_size;
#endif
}
nxt_thread_log_debug("mem cache chunk:%uz alloc: %p", size, p);
return p;
}
static nxt_uint_t
nxt_mem_cache_alloc_chunk(uint8_t *map, nxt_uint_t size)
{
uint8_t mask;
nxt_uint_t n, offset;
offset = 0;
n = 0;
/* The page must have at least one free chunk. */
for ( ;; ) {
if (map[n] != 0xff) {
mask = 0x80;
do {
if ((map[n] & mask) == 0) {
/* A free chunk is found. */
map[n] |= mask;
return offset;
}
offset += size;
mask >>= 1;
} while (mask != 0);
} else {
/* Fast-forward: all 8 chunks are occupied. */
offset += size * 8;
}
n++;
}
}
static nxt_mem_cache_page_t *
nxt_mem_cache_alloc_page(nxt_mem_cache_pool_t *pool)
{
nxt_queue_link_t *link;
nxt_mem_cache_page_t *page;
nxt_mem_cache_block_t *cluster;
if (nxt_queue_is_empty(&pool->free_pages)) {
cluster = nxt_mem_cache_alloc_cluster(pool);
if (nxt_slow_path(cluster == NULL)) {
return NULL;
}
}
link = nxt_queue_first(&pool->free_pages);
nxt_queue_remove(link);
page = nxt_queue_link_data(link, nxt_mem_cache_page_t, link);
return page;
}
static nxt_mem_cache_block_t *
nxt_mem_cache_alloc_cluster(nxt_mem_cache_pool_t *pool)
{
nxt_uint_t n;
nxt_mem_cache_block_t *cluster;
n = pool->cluster_size >> pool->page_size_shift;
cluster = nxt_zalloc(sizeof(nxt_mem_cache_block_t)
+ n * sizeof(nxt_mem_cache_page_t));
if (nxt_slow_path(cluster == NULL)) {
return NULL;
}
/* NXT_MEM_CACHE_CLUSTER_BLOCK type is zero. */
cluster->size = pool->cluster_size;
cluster->start = nxt_memalign(pool->page_alignment, pool->cluster_size);
if (nxt_slow_path(cluster->start == NULL)) {
nxt_free(cluster);
return NULL;
}
n--;
cluster->pages[n].number = n;
nxt_queue_insert_head(&pool->free_pages, &cluster->pages[n].link);
while (n != 0) {
n--;
cluster->pages[n].number = n;
nxt_queue_insert_before(&cluster->pages[n + 1].link,
&cluster->pages[n].link);
}
nxt_rbtree_insert(&pool->pages, &cluster->node);
return cluster;
}
static void *
nxt_mem_cache_alloc_large(nxt_mem_cache_pool_t *pool, size_t alignment,
size_t size)
{
u_char *p;
size_t aligned_size;
uint8_t type;
nxt_mem_cache_block_t *block;
if (nxt_slow_path((size - 1) & size) != 0) {
aligned_size = nxt_align_size(size, sizeof(uintptr_t));
p = nxt_memalign(alignment,
aligned_size + sizeof(nxt_mem_cache_block_t));
if (nxt_slow_path(p == NULL)) {
return NULL;
}
block = (nxt_mem_cache_block_t *) (p + aligned_size);
type = NXT_MEM_CACHE_EMBEDDED_BLOCK;
} else {
block = nxt_malloc(sizeof(nxt_mem_cache_block_t));
if (nxt_slow_path(block == NULL)) {
nxt_free(block);
return NULL;
}
p = nxt_memalign(alignment, size);
if (nxt_slow_path(p == NULL)) {
return NULL;
}
type = NXT_MEM_CACHE_DISCRETE_BLOCK;
}
block->type = type;
block->size = size;
block->start = p;
nxt_rbtree_insert(&pool->pages, &block->node);
return p;
}
static intptr_t
nxt_mem_cache_rbtree_compare(nxt_rbtree_node_t *node1, nxt_rbtree_node_t *node2)
{
nxt_mem_cache_block_t *block1, *block2;
block1 = (nxt_mem_cache_block_t *) node1;
block2 = (nxt_mem_cache_block_t *) node2;
return (uintptr_t) block1->start - (uintptr_t) block2->start;
}
void
nxt_mem_cache_free(nxt_mem_cache_pool_t *pool, void *p)
{
const char *err;
nxt_mem_cache_block_t *block;
nxt_thread_log_debug("mem cache free %p", p);
block = nxt_mem_cache_find_block(&pool->pages, p);
if (nxt_fast_path(block != NULL)) {
if (block->type == NXT_MEM_CACHE_CLUSTER_BLOCK) {
err = nxt_mem_cache_chunk_free(pool, block, p);
} else if (nxt_fast_path(p == block->start)) {
nxt_rbtree_delete(&pool->pages, &block->node);
if (block->type == NXT_MEM_CACHE_DISCRETE_BLOCK) {
nxt_free(block);
}
nxt_free(p);
err = NULL;
} else {
err = "pointer to wrong page";
}
} else {
err = "pointer is out of pool";
}
if (nxt_slow_path(err != NULL)) {
nxt_thread_log_alert("nxt_mem_cache_pool_free(%p): %s", p, err);
}
}
static nxt_mem_cache_block_t *
nxt_mem_cache_find_block(nxt_rbtree_t *tree, u_char *p)
{
nxt_rbtree_node_t *node, *sentinel;
nxt_mem_cache_block_t *block;
node = nxt_rbtree_root(tree);
sentinel = nxt_rbtree_sentinel(tree);
while (node != sentinel) {
block = (nxt_mem_cache_block_t *) node;
if (p < block->start) {
node = node->left;
} else if (p >= block->start + block->size) {
node = node->right;
} else {
return block;
}
}
return NULL;
}
static const char *
nxt_mem_cache_chunk_free(nxt_mem_cache_pool_t *pool,
nxt_mem_cache_block_t *cluster, u_char *p)
{
u_char *start;
uintptr_t offset;
nxt_uint_t n, size, chunk;
nxt_mem_cache_page_t *page;
nxt_mem_cache_slot_t *slot;
n = (p - cluster->start) >> pool->page_size_shift;
start = cluster->start + (n << pool->page_size_shift);
page = &cluster->pages[n];
if (page->size == 0) {
return "page is already free";
}
size = page->size << pool->chunk_size_shift;
if (size != pool->page_size) {
offset = (uintptr_t) (p - start) & (pool->page_size - 1);
chunk = offset / size;
if (nxt_slow_path(offset != chunk * size)) {
return "pointer to wrong chunk";
}
if (nxt_slow_path(nxt_mem_cache_chunk_is_free(page->map, chunk))) {
return "chunk is already free";
}
nxt_mem_cache_chunk_set_free(page->map, chunk);
/* Find a slot with appropriate chunk size. */
for (slot = pool->slots; slot->size < size; slot++) { /* void */ }
if (page->chunks != slot->chunks) {
page->chunks++;
if (page->chunks == 1) {
/*
* Add the page to the head of pool chunk slot list
* of pages with free chunks.
*/
nxt_queue_insert_head(&slot->pages, &page->link);
}
nxt_mem_cache_free_junk(p, size);
return NULL;
} else {
/*
* All chunks are free, remove the page from pool chunk slot
* list of pages with free chunks.
*/
nxt_queue_remove(&page->link);
}
} else if (nxt_slow_path(p != start)) {
return "invalid pointer to chunk";
}
/* Add the free page to the pool's free pages tree. */
page->size = 0;
nxt_queue_insert_head(&pool->free_pages, &page->link);
nxt_mem_cache_free_junk(p, size);
/* Test if all pages in the cluster are free. */
page = cluster->pages;
n = pool->cluster_size >> pool->page_size_shift;
do {
if (page->size != 0) {
return NULL;
}
page++;
n--;
} while (n != 0);
/* Free cluster. */
page = cluster->pages;
n = pool->cluster_size >> pool->page_size_shift;
do {
nxt_queue_remove(&page->link);
page++;
n--;
} while (n != 0);
nxt_rbtree_delete(&pool->pages, &cluster->node);
p = cluster->start;
nxt_free(cluster);
nxt_free(p);
return NULL;
}
const nxt_mem_proto_t nxt_mem_cache_proto = {
(nxt_mem_proto_alloc_t) nxt_mem_cache_alloc,
(nxt_mem_proto_free_t) nxt_mem_cache_free,
};
