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4cf89436d1
nginx/src/core/ngx_slab.c
Ruslan Ermilov 4cf89436d1 Slab: added comment about list heads.
2016-12-07 22:25:37 +03:00

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/*
* Copyright (C) Igor Sysoev
* Copyright (C) Nginx, Inc.
*/
#include <ngx_config.h>
#include <ngx_core.h>
#define NGX_SLAB_PAGE_MASK 3
#define NGX_SLAB_PAGE 0
#define NGX_SLAB_BIG 1
#define NGX_SLAB_EXACT 2
#define NGX_SLAB_SMALL 3
#if (NGX_PTR_SIZE == 4)
#define NGX_SLAB_PAGE_FREE 0
#define NGX_SLAB_PAGE_BUSY 0xffffffff
#define NGX_SLAB_PAGE_START 0x80000000
#define NGX_SLAB_SHIFT_MASK 0x0000000f
#define NGX_SLAB_MAP_MASK 0xffff0000
#define NGX_SLAB_MAP_SHIFT 16
#define NGX_SLAB_BUSY 0xffffffff
#else /* (NGX_PTR_SIZE == 8) */
#define NGX_SLAB_PAGE_FREE 0
#define NGX_SLAB_PAGE_BUSY 0xffffffffffffffff
#define NGX_SLAB_PAGE_START 0x8000000000000000
#define NGX_SLAB_SHIFT_MASK 0x000000000000000f
#define NGX_SLAB_MAP_MASK 0xffffffff00000000
#define NGX_SLAB_MAP_SHIFT 32
#define NGX_SLAB_BUSY 0xffffffffffffffff
#endif
#define ngx_slab_slots(pool) \
(ngx_slab_page_t *) ((u_char *) (pool) + sizeof(ngx_slab_pool_t))
#define ngx_slab_page_type(page) ((page)->prev & NGX_SLAB_PAGE_MASK)
#define ngx_slab_page_prev(page) \
(ngx_slab_page_t *) ((page)->prev & ~NGX_SLAB_PAGE_MASK)
#define ngx_slab_page_addr(pool, page) \
((((page) - (pool)->pages) << ngx_pagesize_shift) \
+ (uintptr_t) (pool)->start)
#if (NGX_DEBUG_MALLOC)
#define ngx_slab_junk(p, size) ngx_memset(p, 0xA5, size)
#elif (NGX_HAVE_DEBUG_MALLOC)
#define ngx_slab_junk(p, size) \
if (ngx_debug_malloc) ngx_memset(p, 0xA5, size)
#else
#define ngx_slab_junk(p, size)
#endif
static ngx_slab_page_t *ngx_slab_alloc_pages(ngx_slab_pool_t *pool,
ngx_uint_t pages);
static void ngx_slab_free_pages(ngx_slab_pool_t *pool, ngx_slab_page_t *page,
ngx_uint_t pages);
static void ngx_slab_error(ngx_slab_pool_t *pool, ngx_uint_t level,
char *text);
static ngx_uint_t ngx_slab_max_size;
static ngx_uint_t ngx_slab_exact_size;
static ngx_uint_t ngx_slab_exact_shift;
void
ngx_slab_init(ngx_slab_pool_t *pool)
{
u_char *p;
size_t size;
ngx_int_t m;
ngx_uint_t i, n, pages;
ngx_slab_page_t *slots, *page;
/* STUB */
if (ngx_slab_max_size == 0) {
ngx_slab_max_size = ngx_pagesize / 2;
ngx_slab_exact_size = ngx_pagesize / (8 * sizeof(uintptr_t));
for (n = ngx_slab_exact_size; n >>= 1; ngx_slab_exact_shift++) {
/* void */
}
}
/**/
pool->min_size = 1 << pool->min_shift;
slots = ngx_slab_slots(pool);
p = (u_char *) slots;
size = pool->end - p;
ngx_slab_junk(p, size);
n = ngx_pagesize_shift - pool->min_shift;
for (i = 0; i < n; i++) {
/* only "next" is used in list head */
slots[i].slab = 0;
slots[i].next = &slots[i];
slots[i].prev = 0;
}
p += n * sizeof(ngx_slab_page_t);
pages = (ngx_uint_t) (size / (ngx_pagesize + sizeof(ngx_slab_page_t)));
pool->pages = (ngx_slab_page_t *) p;
ngx_memzero(pool->pages, pages * sizeof(ngx_slab_page_t));
page = pool->pages;
/* only "next" is used in list head */
pool->free.slab = 0;
pool->free.next = page;
pool->free.prev = 0;
page->slab = pages;
page->next = &pool->free;
page->prev = (uintptr_t) &pool->free;
pool->start = ngx_align_ptr(p + pages * sizeof(ngx_slab_page_t),
ngx_pagesize);
m = pages - (pool->end - pool->start) / ngx_pagesize;
if (m > 0) {
pages -= m;
page->slab = pages;
}
pool->last = pool->pages + pages;
pool->log_nomem = 1;
pool->log_ctx = &pool->zero;
pool->zero = '\0';
}
void *
ngx_slab_alloc(ngx_slab_pool_t *pool, size_t size)
{
void *p;
ngx_shmtx_lock(&pool->mutex);
p = ngx_slab_alloc_locked(pool, size);
ngx_shmtx_unlock(&pool->mutex);
return p;
}
void *
ngx_slab_alloc_locked(ngx_slab_pool_t *pool, size_t size)
{
size_t s;
uintptr_t p, n, m, mask, *bitmap;
ngx_uint_t i, slot, shift, map;
ngx_slab_page_t *page, *prev, *slots;
if (size > ngx_slab_max_size) {
ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, ngx_cycle->log, 0,
"slab alloc: %uz", size);
page = ngx_slab_alloc_pages(pool, (size >> ngx_pagesize_shift)
+ ((size % ngx_pagesize) ? 1 : 0));
if (page) {
p = ngx_slab_page_addr(pool, page);
} else {
p = 0;
}
goto done;
}
if (size > pool->min_size) {
shift = 1;
for (s = size - 1; s >>= 1; shift++) { /* void */ }
slot = shift - pool->min_shift;
} else {
shift = pool->min_shift;
slot = 0;
}
ngx_log_debug2(NGX_LOG_DEBUG_ALLOC, ngx_cycle->log, 0,
"slab alloc: %uz slot: %ui", size, slot);
slots = ngx_slab_slots(pool);
page = slots[slot].next;
if (page->next != page) {
if (shift < ngx_slab_exact_shift) {
do {
bitmap = (uintptr_t *) ngx_slab_page_addr(pool, page);
map = (1 << (ngx_pagesize_shift - shift))
/ (sizeof(uintptr_t) * 8);
for (n = 0; n < map; n++) {
if (bitmap[n] != NGX_SLAB_BUSY) {
for (m = 1, i = 0; m; m <<= 1, i++) {
if (bitmap[n] & m) {
continue;
}
bitmap[n] |= m;
i = ((n * sizeof(uintptr_t) * 8) << shift)
+ (i << shift);
if (bitmap[n] == NGX_SLAB_BUSY) {
for (n = n + 1; n < map; n++) {
if (bitmap[n] != NGX_SLAB_BUSY) {
p = (uintptr_t) bitmap + i;
goto done;
}
}
prev = ngx_slab_page_prev(page);
prev->next = page->next;
page->next->prev = page->prev;
page->next = NULL;
page->prev = NGX_SLAB_SMALL;
}
p = (uintptr_t) bitmap + i;
goto done;
}
}
}
page = page->next;
} while (page);
} else if (shift == ngx_slab_exact_shift) {
do {
if (page->slab != NGX_SLAB_BUSY) {
for (m = 1, i = 0; m; m <<= 1, i++) {
if (page->slab & m) {
continue;
}
page->slab |= m;
if (page->slab == NGX_SLAB_BUSY) {
prev = ngx_slab_page_prev(page);
prev->next = page->next;
page->next->prev = page->prev;
page->next = NULL;
page->prev = NGX_SLAB_EXACT;
}
p = ngx_slab_page_addr(pool, page) + (i << shift);
goto done;
}
}
page = page->next;
} while (page);
} else { /* shift > ngx_slab_exact_shift */
n = ngx_pagesize_shift - (page->slab & NGX_SLAB_SHIFT_MASK);
n = 1 << n;
n = ((uintptr_t) 1 << n) - 1;
mask = n << NGX_SLAB_MAP_SHIFT;
do {
if ((page->slab & NGX_SLAB_MAP_MASK) != mask) {
for (m = (uintptr_t) 1 << NGX_SLAB_MAP_SHIFT, i = 0;
m & mask;
m <<= 1, i++)
{
if (page->slab & m) {
continue;
}
page->slab |= m;
if ((page->slab & NGX_SLAB_MAP_MASK) == mask) {
prev = ngx_slab_page_prev(page);
prev->next = page->next;
page->next->prev = page->prev;
page->next = NULL;
page->prev = NGX_SLAB_BIG;
}
p = ngx_slab_page_addr(pool, page) + (i << shift);
goto done;
}
}
page = page->next;
} while (page);
}
}
page = ngx_slab_alloc_pages(pool, 1);
if (page) {
if (shift < ngx_slab_exact_shift) {
bitmap = (uintptr_t *) ngx_slab_page_addr(pool, page);
s = 1 << shift;
n = (1 << (ngx_pagesize_shift - shift)) / 8 / s;
if (n == 0) {
n = 1;
}
bitmap[0] = (2 << n) - 1;
map = (1 << (ngx_pagesize_shift - shift)) / (sizeof(uintptr_t) * 8);
for (i = 1; i < map; i++) {
bitmap[i] = 0;
}
page->slab = shift;
page->next = &slots[slot];
page->prev = (uintptr_t) &slots[slot] | NGX_SLAB_SMALL;
slots[slot].next = page;
p = ngx_slab_page_addr(pool, page) + s * n;
goto done;
} else if (shift == ngx_slab_exact_shift) {
page->slab = 1;
page->next = &slots[slot];
page->prev = (uintptr_t) &slots[slot] | NGX_SLAB_EXACT;
slots[slot].next = page;
p = ngx_slab_page_addr(pool, page);
goto done;
} else { /* shift > ngx_slab_exact_shift */
page->slab = ((uintptr_t) 1 << NGX_SLAB_MAP_SHIFT) | shift;
page->next = &slots[slot];
page->prev = (uintptr_t) &slots[slot] | NGX_SLAB_BIG;
slots[slot].next = page;
p = ngx_slab_page_addr(pool, page);
goto done;
}
}
p = 0;
done:
ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, ngx_cycle->log, 0,
"slab alloc: %p", (void *) p);
return (void *) p;
}
void *
ngx_slab_calloc(ngx_slab_pool_t *pool, size_t size)
{
void *p;
ngx_shmtx_lock(&pool->mutex);
p = ngx_slab_calloc_locked(pool, size);
ngx_shmtx_unlock(&pool->mutex);
return p;
}
void *
ngx_slab_calloc_locked(ngx_slab_pool_t *pool, size_t size)
{
void *p;
p = ngx_slab_alloc_locked(pool, size);
if (p) {
ngx_memzero(p, size);
}
return p;
}
void
ngx_slab_free(ngx_slab_pool_t *pool, void *p)
{
ngx_shmtx_lock(&pool->mutex);
ngx_slab_free_locked(pool, p);
ngx_shmtx_unlock(&pool->mutex);
}
void
ngx_slab_free_locked(ngx_slab_pool_t *pool, void *p)
{
size_t size;
uintptr_t slab, m, *bitmap;
ngx_uint_t n, type, slot, shift, map;
ngx_slab_page_t *slots, *page;
ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, ngx_cycle->log, 0, "slab free: %p", p);
if ((u_char *) p < pool->start || (u_char *) p > pool->end) {
ngx_slab_error(pool, NGX_LOG_ALERT, "ngx_slab_free(): outside of pool");
goto fail;
}
n = ((u_char *) p - pool->start) >> ngx_pagesize_shift;
page = &pool->pages[n];
slab = page->slab;
type = ngx_slab_page_type(page);
switch (type) {
case NGX_SLAB_SMALL:
shift = slab & NGX_SLAB_SHIFT_MASK;
size = 1 << shift;
if ((uintptr_t) p & (size - 1)) {
goto wrong_chunk;
}
n = ((uintptr_t) p & (ngx_pagesize - 1)) >> shift;
m = (uintptr_t) 1 << (n & (sizeof(uintptr_t) * 8 - 1));
n /= (sizeof(uintptr_t) * 8);
bitmap = (uintptr_t *)
((uintptr_t) p & ~((uintptr_t) ngx_pagesize - 1));
if (bitmap[n] & m) {
if (page->next == NULL) {
slots = ngx_slab_slots(pool);
slot = shift - pool->min_shift;
page->next = slots[slot].next;
slots[slot].next = page;
page->prev = (uintptr_t) &slots[slot] | NGX_SLAB_SMALL;
page->next->prev = (uintptr_t) page | NGX_SLAB_SMALL;
}
bitmap[n] &= ~m;
n = (1 << (ngx_pagesize_shift - shift)) / 8 / (1 << shift);
if (n == 0) {
n = 1;
}
if (bitmap[0] & ~(((uintptr_t) 1 << n) - 1)) {
goto done;
}
map = (1 << (ngx_pagesize_shift - shift)) / (sizeof(uintptr_t) * 8);
for (n = 1; n < map; n++) {
if (bitmap[n]) {
goto done;
}
}
ngx_slab_free_pages(pool, page, 1);
goto done;
}
goto chunk_already_free;
case NGX_SLAB_EXACT:
m = (uintptr_t) 1 <<
(((uintptr_t) p & (ngx_pagesize - 1)) >> ngx_slab_exact_shift);
size = ngx_slab_exact_size;
if ((uintptr_t) p & (size - 1)) {
goto wrong_chunk;
}
if (slab & m) {
if (slab == NGX_SLAB_BUSY) {
slots = ngx_slab_slots(pool);
slot = ngx_slab_exact_shift - pool->min_shift;
page->next = slots[slot].next;
slots[slot].next = page;
page->prev = (uintptr_t) &slots[slot] | NGX_SLAB_EXACT;
page->next->prev = (uintptr_t) page | NGX_SLAB_EXACT;
}
page->slab &= ~m;
if (page->slab) {
goto done;
}
ngx_slab_free_pages(pool, page, 1);
goto done;
}
goto chunk_already_free;
case NGX_SLAB_BIG:
shift = slab & NGX_SLAB_SHIFT_MASK;
size = 1 << shift;
if ((uintptr_t) p & (size - 1)) {
goto wrong_chunk;
}
m = (uintptr_t) 1 << ((((uintptr_t) p & (ngx_pagesize - 1)) >> shift)
+ NGX_SLAB_MAP_SHIFT);
if (slab & m) {
if (page->next == NULL) {
slots = ngx_slab_slots(pool);
slot = shift - pool->min_shift;
page->next = slots[slot].next;
slots[slot].next = page;
page->prev = (uintptr_t) &slots[slot] | NGX_SLAB_BIG;
page->next->prev = (uintptr_t) page | NGX_SLAB_BIG;
}
page->slab &= ~m;
if (page->slab & NGX_SLAB_MAP_MASK) {
goto done;
}
ngx_slab_free_pages(pool, page, 1);
goto done;
}
goto chunk_already_free;
case NGX_SLAB_PAGE:
if ((uintptr_t) p & (ngx_pagesize - 1)) {
goto wrong_chunk;
}
if (!(slab & NGX_SLAB_PAGE_START)) {
ngx_slab_error(pool, NGX_LOG_ALERT,
"ngx_slab_free(): page is already free");
goto fail;
}
if (slab == NGX_SLAB_PAGE_BUSY) {
ngx_slab_error(pool, NGX_LOG_ALERT,
"ngx_slab_free(): pointer to wrong page");
goto fail;
}
n = ((u_char *) p - pool->start) >> ngx_pagesize_shift;
size = slab & ~NGX_SLAB_PAGE_START;
ngx_slab_free_pages(pool, &pool->pages[n], size);
ngx_slab_junk(p, size << ngx_pagesize_shift);
return;
}
/* not reached */
return;
done:
ngx_slab_junk(p, size);
return;
wrong_chunk:
ngx_slab_error(pool, NGX_LOG_ALERT,
"ngx_slab_free(): pointer to wrong chunk");
goto fail;
chunk_already_free:
ngx_slab_error(pool, NGX_LOG_ALERT,
"ngx_slab_free(): chunk is already free");
fail:
return;
}
static ngx_slab_page_t *
ngx_slab_alloc_pages(ngx_slab_pool_t *pool, ngx_uint_t pages)
{
ngx_slab_page_t *page, *p;
for (page = pool->free.next; page != &pool->free; page = page->next) {
if (page->slab >= pages) {
if (page->slab > pages) {
page[page->slab - 1].prev = (uintptr_t) &page[pages];
page[pages].slab = page->slab - pages;
page[pages].next = page->next;
page[pages].prev = page->prev;
p = (ngx_slab_page_t *) page->prev;
p->next = &page[pages];
page->next->prev = (uintptr_t) &page[pages];
} else {
p = (ngx_slab_page_t *) page->prev;
p->next = page->next;
page->next->prev = page->prev;
}
page->slab = pages | NGX_SLAB_PAGE_START;
page->next = NULL;
page->prev = NGX_SLAB_PAGE;
if (--pages == 0) {
return page;
}
for (p = page + 1; pages; pages--) {
p->slab = NGX_SLAB_PAGE_BUSY;
p->next = NULL;
p->prev = NGX_SLAB_PAGE;
p++;
}
return page;
}
}
if (pool->log_nomem) {
ngx_slab_error(pool, NGX_LOG_CRIT,
"ngx_slab_alloc() failed: no memory");
}
return NULL;
}
static void
ngx_slab_free_pages(ngx_slab_pool_t *pool, ngx_slab_page_t *page,
ngx_uint_t pages)
{
ngx_slab_page_t *prev, *join;
page->slab = pages--;
if (pages) {
ngx_memzero(&page[1], pages * sizeof(ngx_slab_page_t));
}
if (page->next) {
prev = ngx_slab_page_prev(page);
prev->next = page->next;
page->next->prev = page->prev;
}
join = page + page->slab;
if (join < pool->last) {
if (ngx_slab_page_type(join) == NGX_SLAB_PAGE) {
if (join->next != NULL) {
pages += join->slab;
page->slab += join->slab;
prev = ngx_slab_page_prev(join);
prev->next = join->next;
join->next->prev = join->prev;
join->slab = NGX_SLAB_PAGE_FREE;
join->next = NULL;
join->prev = NGX_SLAB_PAGE;
}
}
}
if (page > pool->pages) {
join = page - 1;
if (ngx_slab_page_type(join) == NGX_SLAB_PAGE) {
if (join->slab == NGX_SLAB_PAGE_FREE) {
join = ngx_slab_page_prev(join);
}
if (join->next != NULL) {
pages += join->slab;
join->slab += page->slab;
prev = ngx_slab_page_prev(join);
prev->next = join->next;
join->next->prev = join->prev;
page->slab = NGX_SLAB_PAGE_FREE;
page->next = NULL;
page->prev = NGX_SLAB_PAGE;
page = join;
}
}
}
if (pages) {
page[pages].prev = (uintptr_t) page;
}
page->prev = (uintptr_t) &pool->free;
page->next = pool->free.next;
page->next->prev = (uintptr_t) page;
pool->free.next = page;
}
static void
ngx_slab_error(ngx_slab_pool_t *pool, ngx_uint_t level, char *text)
{
ngx_log_error(level, ngx_cycle->log, 0, "%s%s", text, pool->log_ctx);
}
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