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: [email protected] ]

结束