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Date: Fri, 3 Jun 2011 07:23:48 +0900 From: Minchan Kim <minchan.kim@...il.com> To: Andrea Arcangeli <aarcange@...hat.com> Cc: Mel Gorman <mgorman@...e.de>, Mel Gorman <mel@....ul.ie>, akpm@...ux-foundation.org, Ury Stankevich <urykhy@...il.com>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCH] mm: compaction: Abort compaction if too many pages are isolated and caller is asynchronous Hi Andrea, On Fri, Jun 3, 2011 at 6:40 AM, Andrea Arcangeli <aarcange@...hat.com> wrote: > Hello Minchan, > > On Fri, Jun 03, 2011 at 05:21:56AM +0900, Minchan Kim wrote: >> Isn't it rather aggressive? >> I think cursor page is likely to be PageTail rather than PageHead. >> Could we handle it simply with below code? > > It's not so likely, there is small percentage of compound pages that > aren't THP compared to the rest that is either regular pagecache or > anon regular or anon THP or regular shm. If it's THP chances are we I mean we have more tail pages than head pages. So I think we are likely to meet tail pages. Of course, compared to all pages(page cache, anon and so on), compound pages would be very small percentage. > isolated the head and it's useless to insist on more tail pages (at > least for large page size like on x86). Plus we've compaction so I can't understand your point. Could you elaborate it? > insisting and screwing lru ordering isn't worth it, better to be > permissive and abort... in fact I wouldn't dislike to remove the > entire lumpy logic when COMPACTION_BUILD is true, but that alters the > trace too... AFAIK, it's final destination to go as compaction will not break lru ordering if my patch(inorder-putback) is merged. > >> get_page(cursor_page) >> /* The page is freed already */ >> if (1 == page_count(cursor_page)) { >> put_page(cursor_page) >> continue; >> } >> put_page(cursor_page); > > We can't call get_page on an tail page or we break split_huge_page, Why don't we call get_page on tail page if tail page isn't free? Maybe I need investigating split_huge_page. > only an isolated lru can be boosted, if we take the lru_lock and we > check the page is in lru, then we can isolate and pin it safely. > Thanks. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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