On 2016/7/22 17:04, Vlastimil Babka wrote: > On 07/22/2016 10:56 AM, Xishi Qiu wrote: >> Hi, >> >> 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: > > https://lkml.org/lkml/2016/6/24/222 > > especially: > > https://lkml.org/lkml/2016/6/24/214 > >> e.g. >> __alloc_pages_nodemask() >> get_page_from_freelist() >> this is fast path, use use low_wmark_pages() in __zone_watermark_ok() >> >> __alloc_pages_slowpath() >> this is slow path, usually use min_wmark_pages() > > Yes, and compaction should be finished when allocation can succeed, so match > __alloc_pages_slowpath(). >
Sounds reasonable, but now we have kcompactd which called from kswapd, so still use low wmark? Thanks, Xishi Qiu >> >> kswapd >> balance_pgdat() >> use high_wmark_pages() to determine whether zone is balanced >> >> Thanks, >> Xishi Qiu >> > > > . >
