/*
* Copyright (C) Igor Sysoev
* Copyright (C) Nginx, Inc.
*/
#ifndef _NGX_PALLOC_H_INCLUDED_
#define _NGX_PALLOC_H_INCLUDED_
#include <ngx_config.h>
#include <ngx_core.h>
/*
* NGX_MAX_ALLOC_FROM_POOL should be (ngx_pagesize - 1), i.e. 4095 on x86.
* On Windows NT it decreases a number of locked pages in a kernel.
*/
#define NGX_MAX_ALLOC_FROM_POOL (ngx_pagesize - 1)
#define NGX_DEFAULT_POOL_SIZE (16 * 1024)
#define NGX_POOL_ALIGNMENT 16
#define NGX_MIN_POOL_SIZE \
ngx_align((sizeof(ngx_pool_t) + 2 * sizeof(ngx_pool_large_t)), \
NGX_POOL_ALIGNMENT)
typedef void (*ngx_pool_cleanup_pt)(void *data);
typedef struct ngx_pool_cleanup_s ngx_pool_cleanup_t;
struct ngx_pool_cleanup_s {
ngx_pool_cleanup_pt handler;
void *data;
ngx_pool_cleanup_t *next;
};
typedef struct ngx_pool_large_s ngx_pool_large_t;
//大内存结构
struct ngx_pool_large_s {
ngx_pool_large_t *next; //下一个大块内存
void *alloc;//nginx分配的大块内存空间
};
//该结构用来维护内存池的数据块，供用户分配之用
typedef struct {
u_char *last; //当前内存分配结束位置，即下一段可分配内存的起始位置
u_char *end; //内存池结束位置
ngx_pool_t *next; //链接到下一个内存池
ngx_uint_t failed;//统计该内存池不能满足分配请求的次数
} ngx_pool_data_t;
//该结构维护整个内存池的头部信息
//Nginx使用内存池时总是只申请,不释放,使用完毕后直接destroy整个内存池
struct ngx_pool_s {
ngx_pool_data_t d; //数据块
size_t max; //数据块大小，即小块内存的最大值
ngx_pool_t *current; //保存当前内存值
ngx_chain_t *chain; //可以挂一个chain结构
ngx_pool_large_t *large; //分配大块内存用，即超过max的内存请求
ngx_pool_cleanup_t *cleanup; //挂载一些内存池释放的时候，同时释放的资源
ngx_log_t *log;
};
/*ngx_pool_cleanup_t中的*data成员通常指向ngx_pool_cleanup_file_t结构体*/
typedef struct {
ngx_fd_t fd; //文件句柄
u_char *name; //文件名称
ngx_log_t *log; //日志对象
} ngx_pool_cleanup_file_t;
//使用malloc分配内存空间
void *ngx_alloc(size_t size, ngx_log_t *log);
//使用malloc分配内存空间，并且将空间内容初始化为0
void *ngx_calloc(size_t size, ngx_log_t *log);
//通过ngx_create_pool可以创建一个内存池
ngx_pool_t *ngx_create_pool(size_t size, ngx_log_t *log);
void ngx_destroy_pool(ngx_pool_t *pool);
void ngx_reset_pool(ngx_pool_t *pool);
void *ngx_palloc(ngx_pool_t *pool, size_t size); //通过ngx_palloc可以从内存池中分配指定大小的内存. palloc取得的内存是对齐的
void *ngx_pnalloc(ngx_pool_t *pool, size_t size); //pnalloc取得的内存是不对齐的
void *ngx_pcalloc(ngx_pool_t *pool, size_t size); //pcalloc直接调用palloc分配好内存，然后进行一次0初始化操作
void *ngx_pmemalign(ngx_pool_t *pool, size_t size, size_t alignment); //在分配size大小的内存，并按照alignment对齐，然后挂到large字段下
ngx_int_t ngx_pfree(ngx_pool_t *pool, void *p);
ngx_pool_cleanup_t *ngx_pool_cleanup_add(ngx_pool_t *p, size_t size);
void ngx_pool_run_cleanup_file(ngx_pool_t *p, ngx_fd_t fd);
void ngx_pool_cleanup_file(void *data);
void ngx_pool_delete_file(void *data);
#endif /* _NGX_PALLOC_H_INCLUDED_ */
/*
* Copyright (C) Igor Sysoev
* Copyright (C) Nginx, Inc.
*/
#include <ngx_config.h>
#include <ngx_core.h>
static void *ngx_palloc_block(ngx_pool_t *pool, size_t size);
static void *ngx_palloc_large(ngx_pool_t *pool, size_t size);
//通过ngx_create_pool可以创建一个内存池
ngx_pool_t *
ngx_create_pool(size_t size, ngx_log_t *log)
{
ngx_pool_t *p;
p = ngx_memalign(NGX_POOL_ALIGNMENT, size, log); // 分配内存函数，uinx,windows分开走
if (p == NULL) {
return NULL;
}
p->d.last = (u_char *) p + sizeof(ngx_pool_t); //初始指向 ngx_pool_t 结构体后面
p->d.end = (u_char *) p + size; //整个结构的结尾后面
p->d.next = NULL;
p->d.failed = 0;
//sizeof(ngx_pool_t)用来存储自身
size = size - sizeof(ngx_pool_t);
p->max = (size < NGX_MAX_ALLOC_FROM_POOL) ? size : NGX_MAX_ALLOC_FROM_POOL; //最大不超过 NGX_MAX_ALLOC_FROM_POOL,也就是getpagesize()-1 大小
p->current = p;
p->chain = NULL;
p->large = NULL;
p->cleanup = NULL;
p->log = log;
return p;
}
//销毁内存池
void
ngx_destroy_pool(ngx_pool_t *pool)
{
ngx_pool_t *p, *n;
ngx_pool_large_t *l;
ngx_pool_cleanup_t *c;
// 遍历节点上的各个节点
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); //释放节点占用的内存
}
}
//对大块数据内存的清理
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); // 直接ngx_free，宏，本质是free
}
}
#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
for (p = pool, n = pool->d.next; /* void */; p = n, n = n->d.next) {
ngx_free(p);
if (n == NULL) {
break;
}
}
}
//重置，将内存池恢复到初始分配的状态
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); //释放大块内存
}
}
pool->large = NULL;
for (p = pool; p; p = p->d.next) {
p->d.last = (u_char *) p + sizeof(ngx_pool_t); //小块内存结尾指针指向刚分配的位置，其中的数据将被覆盖
}
}
//ngx_palloc相对ngx_pnalloc，其会将申请的内存大小向上扩增到NGX_ALIGNMENT的倍数，以方便内存对齐，减少内存访问次数。
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); // 对齐内存指针，加快存取速度
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);
}
//size过大，需要在大数据块内存链表上申请内存空间
return ngx_palloc_large(pool, size);
}
/* 原理和ngx_alloc一样，只是没有考虑数据对齐*/
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);
}
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);
m = ngx_memalign(NGX_POOL_ALIGNMENT, psize, pool->log);
if (m == NULL) {
return NULL;
}
new = (ngx_pool_t *) m;
new->d.end = m + psize;
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;
}
//控制大块内存的申请
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); // 在大数据块链表中申请调用了ngx_alloc
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;
}
//控制大块内存的释放。注意，这个函数只会释放大内存，不会释放其对应的头部结构，遗留下来的头部结构会做下一次申请大内存之用
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;
}
//ngx_pcalloc其只是ngx_palloc的一个封装，将申请到的内存全部初始化为0。
void *
ngx_pcalloc(ngx_pool_t *pool, size_t size)
{
void *p;
p = ngx_palloc(pool, size);
if (p) {
ngx_memzero(p, size); //初始化
}
return p;
}
// 用于向内存回收链表中添加节点数据
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); // 申请存放目标数据的空间
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;
}
}
}
}
//关闭文件句柄
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_t err;
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
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