bgwriter_delay — specifies the delay between the activity rounds for the background writer. The default value is 200 milliseconds.bgwriter_lru_maxpages —In each round, no more than this many buffers will be written by the background writer. Setting this to zero disables background writing. The default value is 100 buffers.bgwriter_lru_multiplier
bgwriter_delay -- 表示多久写入一次，默认200ms bgwriter_lru_maxpages -- 在单个轮次（即上述 delay 间隔后的一次运行）中，bgwriter 最多能写入多少个页面。 bgwriter_lru_multiplier -- 这是一个相对智能的比例系数，用于根据当前系统的繁忙程度动态估算下次需要写入的页面数。 调大（如 4.0 或更高）：bgwriter 会变得更“激进”，预估会产生更多空位，适合突发性写入较多的场景。
调小：写入更保守