On Fri, 19 Feb 2010, Balbir Singh wrote: > >> zone_reclaim. The others back off and try the next zone in the zonelist > >> instead. I'm not sure what the original intention was but most likely it > >> was to prevent too many parallel reclaimers in the same zone potentially > >> dumping out way more data than necessary. > > > > Yes it was to prevent concurrency slowing down reclaim. At that time the > > number of processors per NUMA node was 2 or so. The number of pages that > > are reclaimed is limited to avoid tossing too many page cache pages. > > > > That is interesting, I always thought it was to try and free page > cache first. For example with zone->min_unmapped_pages, if > zone_pagecache_reclaimable is greater than unmapped pages, we start > reclaim the cached pages first. The min_unmapped_pages almost sounds > like the higher level watermark - or am I misreading the code.
Indeed the purpose is to free *old* page cache pages. The min_unmapped_pages is to protect a mininum of the page cache pages / fs metadata from zone reclaim so that ongoing file I/O is not impacted. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
