函数buf_page_init_for_read
/********************************************************************//**
Function which inits a page for read to the buffer buf_pool. If the page is
(1) already in buf_pool, or
(2) if we specify to read only ibuf pages and the page is not an ibuf page, or
(3) if the space is deleted or being deleted,
then this function does nothing.
Sets the io_fix flag to BUF_IO_READ and sets a non-recursive exclusive lock
on the buffer frame. The io-handler must take care that the flag is cleared
and the lock released later.
@return pointer to the block or NULL */
UNIV_INTERN
buf_page_t*
buf_page_init_for_read(
/*===================*/
ulint* err, /*!< out: DB_SUCCESS or DB_TABLESPACE_DELETED */
ulint mode, /*!< in: BUF_READ_IBUF_PAGES_ONLY, ... */
ulint space, /*!< in: space id */
ulint zip_size,/*!< in: compressed page size, or 0 */
ibool unzip, /*!< in: TRUE=request uncompressed page */
ib_int64_t tablespace_version,
/*!< in: prevents reading from a wrong
version of the tablespace in case we have done
DISCARD + IMPORT */
ulint offset) /*!< in: page number */
{
buf_block_t* block;
buf_page_t* bpage = NULL;
buf_page_t* watch_page;
mtr_t mtr;
ulint fold;
ibool lru = FALSE;
void* data;
buf_pool_t* buf_pool = buf_pool_get(space, offset);
ut_ad(buf_pool);
*err = DB_SUCCESS;
if (mode == BUF_READ_IBUF_PAGES_ONLY) {
/* It is a read-ahead within an ibuf routine */
ut_ad(!ibuf_bitmap_page(zip_size, offset));
ibuf_mtr_start(&mtr);
if (!recv_no_ibuf_operations
&& !ibuf_page(space, zip_size, offset, &mtr)) {
ibuf_mtr_commit(&mtr);
return(NULL);
}
} else {
ut_ad(mode == BUF_READ_ANY_PAGE);
}
if (zip_size && UNIV_LIKELY(!unzip)
&& UNIV_LIKELY(!recv_recovery_is_on())) {
block = NULL;
} else { /** *按理说 会走到这里 zip_size 为0 ,非压缩页 * * */
block = buf_LRU_get_free_block(buf_pool); //获得一块余闲的block free_list->uzip_lru->common_lru顺序 详见
ut_ad(block);
ut_ad(buf_pool_from_block(block) == buf_pool);
}
fold = buf_page_address_fold(space, offset);
buf_pool_mutex_enter(buf_pool);
watch_page = buf_page_hash_get_low(buf_pool, space, offset, fold);
if (watch_page && !buf_pool_watch_is_sentinel(buf_pool, watch_page)) {
/* The page is already in the buffer pool. */
watch_page = NULL;
err_exit:
if (block) {
mutex_enter(&block->mutex);
buf_LRU_block_free_non_file_page(block);
mutex_exit(&block->mutex);
}
bpage = NULL;
goto func_exit;
}
if (fil_tablespace_deleted_or_being_deleted_in_mem(
space, tablespace_version)) {
/* The page belongs to a space which has been
deleted or is being deleted. */
*err = DB_TABLESPACE_DELETED;
goto err_exit;
}
if (block) {
bpage = &block->page;
mutex_enter(&block->mutex);
ut_ad(buf_pool_from_bpage(bpage) == buf_pool);
buf_page_init(buf_pool, space, offset, fold, zip_size, block); //详见 /* The block must be put to the LRU list, to the old blocks */
buf_LRU_add_block(bpage, TRUE/* to old blocks */);
/* We set a pass-type x-lock on the frame because then
the same thread which called for the read operation
(and is running now at this point of code) can wait
for the read to complete by waiting for the x-lock on
the frame; if the x-lock were recursive, the same
thread would illegally get the x-lock before the page
read is completed. The x-lock is cleared by the
io-handler thread. */
rw_lock_x_lock_gen(&block->lock, BUF_IO_READ);
buf_page_set_io_fix(bpage, BUF_IO_READ);//设置bpage->io_fix为BUF_IO_READ,表示将从磁盘读取Page
if (UNIV_UNLIKELY(zip_size)) {
/* buf_pool->mutex may be released and
reacquired by buf_buddy_alloc(). Thus, we
must release block->mutex in order not to
break the latching order in the reacquisition
of buf_pool->mutex. We also must defer this
operation until after the block descriptor has
been added to buf_pool->LRU and
buf_pool->page_hash. */
mutex_exit(&block->mutex);
data = buf_buddy_alloc(buf_pool, zip_size, &lru);
mutex_enter(&block->mutex);
block->page.zip.data = data;
/* To maintain the invariant
block->in_unzip_LRU_list
== buf_page_belongs_to_unzip_LRU(&block->page)
we have to add this block to unzip_LRU
after block->page.zip.data is set. */
ut_ad(buf_page_belongs_to_unzip_LRU(&block->page));
buf_unzip_LRU_add_block(block, TRUE);
}
mutex_exit(&block->mutex);
} else {
/* The compressed page must be allocated before the
control block (bpage), in order to avoid the
invocation of buf_buddy_relocate_block() on
uninitialized data. */
data = buf_buddy_alloc(buf_pool, zip_size, &lru);
/* If buf_buddy_alloc() allocated storage from the LRU list,
it released and reacquired buf_pool->mutex. Thus, we must
check the page_hash again, as it may have been modified. */
if (UNIV_UNLIKELY(lru)) {
watch_page = buf_page_hash_get_low(
buf_pool, space, offset, fold);
if (watch_page
&& !buf_pool_watch_is_sentinel(buf_pool,
watch_page)) {
/* The block was added by some other thread. */
watch_page = NULL;
buf_buddy_free(buf_pool, data, zip_size);
bpage = NULL;
goto func_exit;
}
}
bpage = buf_page_alloc_descriptor();
/* Initialize the buf_pool pointer. */
bpage->buf_pool_index = buf_pool_index(buf_pool);
page_zip_des_init(&bpage->zip);
page_zip_set_size(&bpage->zip, zip_size);
bpage->zip.data = data;
mutex_enter(&buf_pool->zip_mutex);
UNIV_MEM_DESC(bpage->zip.data,
page_zip_get_size(&bpage->zip), bpage);
buf_page_init_low(bpage);
bpage->state = BUF_BLOCK_ZIP_PAGE;
bpage->space = space;
bpage->offset = offset;
#ifdef UNIV_DEBUG
bpage->in_page_hash = FALSE;
bpage->in_zip_hash = FALSE;
bpage->in_flush_list = FALSE;
bpage->in_free_list = FALSE;
bpage->in_LRU_list = FALSE;
#endif /* UNIV_DEBUG */
ut_d(bpage->in_page_hash = TRUE);
if (UNIV_LIKELY_NULL(watch_page)) {
/* Preserve the reference count. */
ulint buf_fix_count = watch_page->buf_fix_count;
ut_a(buf_fix_count > );
bpage->buf_fix_count += buf_fix_count;
ut_ad(buf_pool_watch_is_sentinel(buf_pool, watch_page));
buf_pool_watch_remove(buf_pool, fold, watch_page);
}
HASH_INSERT(buf_page_t, hash, buf_pool->page_hash, fold,
bpage);
/* The block must be put to the LRU list, to the old blocks
The zip_size is already set into the page zip */
buf_LRU_add_block(bpage, TRUE/* to old blocks */);
#if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG
buf_LRU_insert_zip_clean(bpage);
#endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */
buf_page_set_io_fix(bpage, BUF_IO_READ);
mutex_exit(&buf_pool->zip_mutex);
}
buf_pool->n_pend_reads++;
func_exit:
buf_pool_mutex_exit(buf_pool);
if (mode == BUF_READ_IBUF_PAGES_ONLY) {
ibuf_mtr_commit(&mtr);
}
ut_ad(!bpage || buf_page_in_file(bpage));
return(bpage);
}
函数buf_page_init_for_read的更多相关文章
- InnoDB源码分析--缓冲池(二)
转载请附原文链接:http://www.cnblogs.com/wingsless/p/5578727.html 上一篇中我简单的分析了一下InnoDB缓冲池LRU算法的相关源码,其实说不上是分析,应 ...
- 服务器IO瓶颈对MySQL性能的影响
[背景] 之前我们碰到一些MySQL的性能问题,比如服务器日志备份时可能会导致慢查询增多,一句简单的select或insert语句可能执行几秒,IO负载较高的服务器更容易出现并发线程数升高,CPU上升 ...
- Python 小而美的函数
python提供了一些有趣且实用的函数,如any all zip,这些函数能够大幅简化我们得代码,可以更优雅的处理可迭代的对象,同时使用的时候也得注意一些情况 any any(iterable) ...
- 探究javascript对象和数组的异同,及函数变量缓存技巧
javascript中最经典也最受非议的一句话就是:javascript中一切皆是对象.这篇重点要提到的,就是任何jser都不陌生的Object和Array. 有段时间曾经很诧异,到底两种数据类型用来 ...
- JavaScript权威指南 - 函数
函数本身就是一段JavaScript代码,定义一次但可能被调用任意次.如果函数挂载在一个对象上,作为对象的一个属性,通常这种函数被称作对象的方法.用于初始化一个新创建的对象的函数被称作构造函数. 相对 ...
- C++对C的函数拓展
一,内联函数 1.内联函数的概念 C++中的const常量可以用来代替宏常数的定义,例如:用const int a = 10来替换# define a 10.那么C++中是否有什么解决方案来替代宏代码 ...
- 菜鸟Python学习笔记第一天:关于一些函数库的使用
2017年1月3日 星期二 大一学习一门新的计算机语言真的很难,有时候连函数拼写出错查错都能查半天,没办法,谁让我英语太渣. 关于计算机语言的学习我想还是从C语言学习开始为好,Python有很多语言的 ...
- javascript中的this与函数讲解
前言 javascript中没有块级作用域(es6以前),javascript中作用域分为函数作用域和全局作用域.并且,大家可以认为全局作用域其实就是Window函数的函数作用域,我们编写的js代码, ...
- 复杂的 Hash 函数组合有意义吗?
很久以前看到一篇文章,讲某个大网站储存用户口令时,会经过十分复杂的处理.怎么个复杂记不得了,大概就是先 Hash,结果加上一些特殊字符再 Hash,结果再加上些字符.再倒序.再怎么怎么的.再 Hash ...
随机推荐
- 初涉Node.js
Node.js的是建立在Chrome的JavaScript的运行时,可方便地构建快速,可扩展的网络应用程序的平台. Node.js使用事件驱动.非阻塞I/ O模型,是轻量级.高效.完美的跨分布式设备运 ...
- SpringMVC+redis整合
在网络上有一个很多人转载的springmvc+redis整合的案例,不过一直不完整,也是被各种人装来转去,现在基本将该框架搭建起来. package com.pudp.bae.base; import ...
- win7 telnet命令无法使用
很多做网络测试的同学发现安装win7后,无法使用telnet命令了,提示“telnet不是内部或外部命令,也不是可运行的程序”,但是很需要在win7中使用telnet工具,怎么办? 首先你要要确认你的 ...
- UVALive 4872 Underground Cables 最小生成树
题目链接: 题目 Underground Cables Time Limit: 3000MS Memory Limit: Unknown 64bit IO Format: %lld & %ll ...
- maven工程的如何进行代码调试
1.maven项目的父项目右键选择:maven build 注意: 1.选择Browser workspace,让BaseDirectory变成:${***}形式. 2. ...
- EXT4.2--Ext Designer 使用
前言: “画EXT”是一个美好的想法,如果有一款可视化工具能够只需进行拖拽而设计EXT,生成代码--那真是一件美丽的事.然而现实是,即使是为Eclipse装上EXT插件,用上idea,手写代码的提示也 ...
- Asp.Net修改上传文件大小限制(修改web.config)
i. Configuration节点下 <system.webServer> <security> <requestFiltering> <!--单位为字节 ...
- 【C++基础】构造函数
说说你对构造函数的理解? 构造函数:对象创建时,利用特定的值构造对象(不是构造类),将对象初始化(保证数据成员有初始值),是类的一个public 函数 ① 与类同名 ② 无返回值 ③ 声明 ...
- Tries
trie,又称前缀树或字典樹,是一种有序树,用于保存关联数组,其中的键通常是字符串.与二叉查找树不同,键不是直接保存在节点中,而是由节点在树中的位置决定.一个节点的所有子孙都有相同的前缀,也就是这个节 ...
- SDUT1500 Message Flood
以前做过的用的字典树,可是貌似现在再用超内存....求解释... 问了LYN用的map函数做的,又去小小的学了map函数.... http://wenku.baidu.com/view/0b08cec ...