On Fri, Oct 28, 2011 at 01:11:55PM +0800, Shaohua Li wrote: > On Fri, 2011-10-28 at 07:34 +0800, Minchan Kim wrote: > > On Tue, Oct 25, 2011 at 10:59:40AM +0800, Shaohua Li wrote: > > > With current logic, if page reclaim finds a huge page, it will just reclaim > > > the head page and leave tail pages reclaimed later. Let's take an example, > > > lru list has page A and B, page A is huge page: > > > 1. page A is isolated > > > 2. page B is isolated > > > 3. shrink_page_list() adds page A to swap page cache. so page A is split. > > > page A+1, page A+2, ... are added to lru list. > > > 4. shrink_page_list() adds page B to swap page cache. > > > 5. page A and B is written out and reclaimed. > > > 6. page A+1, A+2 ... is isolated and reclaimed later. > > > So the reclaim order is A, B, ...(maybe other pages), A+1, A+2 ... > > > > I don't see your code yet but have a question. > > You mitigate this problem by 4/5 which could add subpages into lru tail > > so subpages would reclaim next interation of reclaim. > > > > What do we need 5/5? > > Do I miss something? > Both patches are required. without this patch, current page reclaim will > only reclaim the first page of a huge page, because the hugepage isn't > split yet. The hugepage is split when the first page is being written to > swap, which is too later and page reclaim might already isolated a lot > of pages. When split happens, subpages would be located in tail of LRU by your 4/5. (Assume tail of LRU is old age). In addtion, isolation happens 32 page chunk so the subpages would be isolated and reclaimed in next iteration. I think 32 pages are not too many. What do you think about it? -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>