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:  ]

结束