Ngnix 源码学习----内存池的申请
这篇文章，主要是对代码的注释。就是对内存池的销毁，以及如何使用内存池的内存。如果 对内存的结构已经很了解，那么，对以下代码就很好理解了////销毁内存池 基本都是链表的基本操作。void
ngx_destroy_pool(ngx_pool_t *pool)
{
ngx_pool_t *p, *n;
ngx_pool_large_t *l;
ngx_pool_cleanup_t*c;
///根据注册的ngx_pool_cleanup_s 来逐个销毁内存
for (c = pool->cleanup; c; c = c->next) {
if (c->handler) {
ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, pool->log, 0,
"run cleanup: %p", c);
c->handler(c->data);
}
}
///销毁大大内存块
for (l = pool->large; l; l = l->next) {
ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, pool->log, 0, "free: %p", l->alloc);
if (l->alloc) {
ngx_free(l->alloc);
}
}
#if (NGX_DEBUG)
/*
* we could allocate the pool->log from this pool
* so we cannot use this log while free()ing the pool
*/
for (p = pool, n = pool->d.next; /* void */; p = n, n = n->d.next) {
ngx_log_debug2(NGX_LOG_DEBUG_ALLOC, pool->log, 0,
"free: %p, unused: %uz", p, p->d.end - p->d.last);
if (n == NULL) {
break;
}
}
#endif
///普通销毁，
for (p = pool, n = pool->d.next; /* void */; p = n, n = n->d.next) {
ngx_free(p);
if (n == NULL) {
break;
}
}
}
////充值内存池，先销毁，再重新分配内存
void
ngx_reset_pool(ngx_pool_t *pool)
{
ngx_pool_t *p;
ngx_pool_large_t*l;
for (l = pool->large; l; l = l->next) {
if (l->alloc) {
ngx_free(l->alloc);
}
}
pool->large = NULL;
for (p = pool; p; p = p->d.next) {
p->d.last = (u_char *) p + sizeof(ngx_pool_t);
}
}
/////这个方法就是 申请了内存后，
///对内存的使用了。
void *
ngx_palloc(ngx_pool_t *pool, size_t size)
{
u_char *m;
ngx_pool_t*p;
if (size <= pool->max) {
p = pool->current;
do {
m = ngx_align_ptr(p->d.last, NGX_ALIGNMENT);
if ((size_t) (p->d.end - m) >= size) {
p->d.last = m + size;
return m;
}
p = p->d.next;
} while (p);
return ngx_palloc_block(pool, size);///内存不够了，申请下一块内存池链表结构
}
return ngx_palloc_large(pool, size);/////申请大内存池块。
}
///同上。
void *
ngx_pnalloc(ngx_pool_t *pool, size_t size)
{
u_char *m;
ngx_pool_t*p;
if (size <= pool->max) {
p = pool->current;
do {
m = p->d.last;
if ((size_t) (p->d.end - m) >= size) {
p->d.last = m + size;
return m;
}
p = p->d.next;
} while (p);
return ngx_palloc_block(pool, size);
}
return ngx_palloc_large(pool, size);
}
////申请下一个内存块。
static void *
ngx_palloc_block(ngx_pool_t *pool, size_t size)
{
u_char *m;
size_t psize;
ngx_pool_t*p, *new, *current;
psize = (size_t) (pool->d.end - (u_char *) pool); //计算pool大小
m = ngx_memalign(NGX_POOL_ALIGNMENT, psize, pool->log);////申请psize大小的内存
if (m == NULL) {
return NULL;
}
new = (ngx_pool_t *) m; //给new。
new->d.end = m + psize;//在额外申一个等大小的内存 ，设置end 值
new->d.next = NULL;
new->d.failed = 0;
m += sizeof(ngx_pool_data_t);
m = ngx_align_ptr(m, NGX_ALIGNMENT);
new->d.last = m + size;
current = pool->current;
for (p = current; p->d.next; p = p->d.next) {
if (p->d.failed++ > 4) {
current = p->d.next;
}
}
p->d.next = new;
pool->current = current ? current : new;
return m;
}
////申请大内存块。
static void *
ngx_palloc_large(ngx_pool_t *pool, size_t size)
{
void *p;
ngx_uint_t n;
ngx_pool_large_t*large;
p = ngx_alloc(size, pool->log);
if (p == NULL) {
return NULL;
}
n = 0;
for (large = pool->large; large; large = large->next) {
if (large->alloc == NULL) {
large->alloc = p;
return p;
}
if (n++ > 3) {
break;
}
}
large = ngx_palloc(pool, sizeof(ngx_pool_large_t));
if (large == NULL) {
ngx_free(p);
return NULL;
}
large->alloc = p;
large->next = pool->large;
pool->large = large;
return p;
}
void *
ngx_pmemalign(ngx_pool_t *pool, size_t size, size_t alignment)
{
void *p;
ngx_pool_large_t*large;
p = ngx_memalign(alignment, size, pool->log);
if (p == NULL) {
return NULL;
}
large = ngx_palloc(pool, sizeof(ngx_pool_large_t));
if (large == NULL) {
ngx_free(p);
return NULL;
}
large->alloc = p;
large->next = pool->large;
pool->large = large;
return p;
}
////释放内存内存。基本的链表操作
ngx_int_t
ngx_pfree(ngx_pool_t *pool, void *p)
{
ngx_pool_large_t*l;
for (l = pool->large; l; l = l->next) {
if (p == l->alloc) {
ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, pool->log, 0,
"free: %p", l->alloc);
ngx_free(l->alloc);
l->alloc = NULL;
return NGX_OK;
}
}
return NGX_DECLINED;
}
void *
ngx_pcalloc(ngx_pool_t *pool, size_t size)
{
void *p;
p = ngx_palloc(pool, size);
if (p) {
ngx_memzero(p, size);
}
return p;
}
/////注册cleanup的一个内存池分配
ngx_pool_cleanup_t *
ngx_pool_cleanup_add(ngx_pool_t *p, size_t size)
{
ngx_pool_cleanup_t*c;
c = ngx_palloc(p, sizeof(ngx_pool_cleanup_t));
if (c == NULL) {
return NULL;
}
if (size) {
c->data = ngx_palloc(p, size);
if (c->data == NULL) {
return NULL;
}
} else {
c->data = NULL;
}
c->handler = NULL;
c->next = p->cleanup;
p->cleanup = c;
ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, p->log, 0, "add cleanup: %p", c);
return c;
}
void
ngx_pool_run_cleanup_file(ngx_pool_t *p, ngx_fd_t fd)
{
ngx_pool_cleanup_t *c;
ngx_pool_cleanup_file_t*cf;
for (c = p->cleanup; c; c = c->next) {
if (c->handler == ngx_pool_cleanup_file) {
cf = c->data;
if (cf->fd == fd) {
c->handler(cf);
c->handler = NULL;
return;
}
}
}
}
void
ngx_pool_cleanup_file(void *data)
{
ngx_pool_cleanup_file_t*c = data;
ngx_log_debug1(NGX_LOG_DEBUG_ALLOC, c->log, 0, "file cleanup: fd:%d",
c->fd);
if (ngx_close_file(c->fd) == NGX_FILE_ERROR) {
ngx_log_error(NGX_LOG_ALERT, c->log, ngx_errno,
ngx_close_file_n " \"%s\" failed", c->name);
}
}
void
ngx_pool_delete_file(void *data)
{
ngx_pool_cleanup_file_t*c = data;
ngx_err_terr;
ngx_log_debug2(NGX_LOG_DEBUG_ALLOC, c->log, 0, "file cleanup: fd:%d %s",
c->fd, c->name);
if (ngx_delete_file(c->name) == NGX_FILE_ERROR) {
err = ngx_errno;
if (err != NGX_ENOENT) {
ngx_log_error(NGX_LOG_CRIT, c->log, err,
ngx_delete_file_n " \"%s\" failed", c->name);
}
}
if (ngx_close_file(c->fd) == NGX_FILE_ERROR) {
ngx_log_error(NGX_LOG_ALERT, c->log, ngx_errno,
ngx_close_file_n " \"%s\" failed", c->name);
}
}
#if 0
static void *
ngx_get_cached_block(size_t size)
{
void *p;
ngx_cached_block_slot_t*slot;
if (ngx_cycle->cache == NULL) {
return NULL;
}
slot = &ngx_cycle->cache[(size + ngx_pagesize - 1) / ngx_pagesize];
slot->tries++;
if (slot->number) {
p = slot->block;
slot->block = slot->block->next;
slot->number--;
return p;
}
return NULL;
}
#endif
下面给几个图片以帮助大家理解。不是我画的
基本的内存数据结构
内存配图，很清晰了，都是链表的操作
看完之后，已经对ngnix的内存池的分配有很清晰的认识了，以后写个内存可以借鉴他的。哈哈，
更多文章欢迎访问：http://blog.csdn.net/wallwind
作者：wallwind 发表于2012-4-16 0:18:56 原文链接
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