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
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