Messages in this thread | | | Date | Fri, 28 Oct 2011 08:19:28 +0900 | From | Minchan Kim <> | Subject | Re: [patch 4/5]thp: correct order in lru list for split huge page |
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On Tue, Oct 25, 2011 at 10:59:37AM +0800, Shaohua Li wrote: > If a huge page is split, all the subpages should live in lru list adjacently > because they should be taken as a whole. > In page split, with current code: > a. if huge page is in lru list, the order is: page, page+HPAGE_PMD_NR-1, > page + HPAGE_PMD_NR-2, ..., page + 1(in lru page reclaim order) > b. otherwise, the order is: page, ..other pages.., page + 1, page + 2, ...(in > lru page reclaim order). page + 1 ... page + HPAGE_PMD_NR - 1 are in the lru > reclaim tail. > > In case a, the order is wrong. In case b, page is isolated (to be reclaimed), > but other tail pages will not soon. > > With below patch: > in case a, the order is: page, page + 1, ... page + HPAGE_PMD_NR-1(in lru page > reclaim order). > in case b, the order is: page + 1, ... page + HPAGE_PMD_NR-1 (in lru page reclaim > order). The tail pages are in the lru reclaim head. > > Signed-off-by: Shaohua Li <shaohua.li@intel.com>
In case of a, it doesn't matter ordering of subpages. As a huge page, age of sub pages are same.
In case of b, what a page is located in tail and other subpages are located in head isn't critical problem.
Having said that, it's more consistent and simple patch. So I like that. Nice catch, Shaohua!
Reviewed-by: Minchan Kim <minchan.kim@gmail.com> -- Kind regards, Minchan Kim
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