Hi, all. In "mm/page_alloc.c: __setup_per_zone_wmarks(void)" Look this: --- snip --- zone->watermark[WMARK_LOW] = min_wmark_pages(zone) + (tmp >> 2); zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + (tmp >> 1); --- snip --- after min_wmark_pages(zone)(that is watermark[WMARK_MIN]) is calculated, the watermark[WMARK_HIGH] and watermark[WMARK_LOW] are based on it. And FYI, for non-highmem zones, watermark[WMARK_MIN] is exactly tmp. That said, watermark[WMARK_HIGH] = 1.5 times watermark[WMARK_MIN] watermark[WMARK_LOW] = 1.25 times watermark[WMARK_MIN] So we came to that question, are the relation among them are just established by usage or just by empirical formula? -- Regards, Zhan Jianyu