对PostgreSQL中bufmgr.c的进一步学习

开始

重要的是：必须了解到 静态变量的使用，它们是贯穿其BgBufferSync 的主线。在一次次调用中始终存在，值也在累积。

bool                    
BgBufferSync(void)                    
{                    
                    
    /* info obtained from freelist.c */                
    int        strategy_buf_id;        
    uint32     strategy_passes;        
    uint32     recent_alloc;        
                    
    /*                
     * Information saved between calls so we can determine the strategy                
     * point's advance rate and avoid scanning already-cleaned buffers.                
     */                
    static           bool          saved_info_valid = false;                
    static           int        prev_strategy_buf_id;        
    static          uint32         prev_strategy_passes;        
    static          int        next_to_clean;        
    static     uint32     next_passes;        
                    
                    
    /* Moving averages of allocation rate and clean-buffer density */                
    static     float     smoothed_alloc = 0;        
    static     float     smoothed_density = 10.0;        
                    
        ......
}

 [作者：技术者高健@博客园  mail: luckyjackgao@gmail.com ]

结束