Re: mm/compact: why use low watermark to determine whether compact is finished instead of use high watermark?
From: Vlastimil Babka
Date: Fri Jul 22 2016 - 05:04:28 EST
On 07/22/2016 10:56 AM, Xishi Qiu wrote:
I find all the watermarks in mm/compaction.c are low_wmark_pages(),
so why not use high watermark to determine whether compact is finished?
Why would you use high watermark? Quite the opposite, I want to move
towards min watermark (precisely, the one in alloc_flags which is
usually min) in this series:
this is fast path, use use low_wmark_pages() in __zone_watermark_ok()
this is slow path, usually use min_wmark_pages()
Yes, and compaction should be finished when allocation can succeed, so
use high_wmark_pages() to determine whether zone is balanced