Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755081Ab2FDOWz (ORCPT ); Mon, 4 Jun 2012 10:22:55 -0400 Received: from mail-ee0-f46.google.com ([74.125.83.46]:36984 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753795Ab2FDOWy convert rfc822-to-8bit (ORCPT ); Mon, 4 Jun 2012 10:22:54 -0400 Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Bartlomiej Zolnierkiewicz" Cc: "Minchan Kim" , "Hugh Dickins" , "Linus Torvalds" , "Kyungmin Park" , "Marek Szyprowski" , "Mel Gorman" , "Rik van Riel" , "Dave Jones" , "Andrew Morton" , "Cong Wang" , "Markus Trippelsdorf" Subject: Re: [PATCH v9] mm: compaction: handle incorrect MIGRATE_UNMOVABLE type pageblocks References: <201206041543.56917.b.zolnierkie@samsung.com> Date: Mon, 04 Jun 2012 16:22:51 +0200 MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT From: "Michal Nazarewicz" Message-ID: In-Reply-To: <201206041543.56917.b.zolnierkie@samsung.com> User-Agent: Opera Mail/12.00 (Linux) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3045 Lines: 95 On Mon, 04 Jun 2012 15:43:56 +0200, Bartlomiej Zolnierkiewicz wrote: > +/* > + * Returns true if MIGRATE_UNMOVABLE pageblock can be successfully > + * converted to MIGRATE_MOVABLE type, false otherwise. > + */ > +static bool can_rescue_unmovable_pageblock(struct page *page, bool locked) > +{ > + unsigned long pfn, start_pfn, end_pfn; > + struct page *start_page, *end_page, *cursor_page; > + > + pfn = page_to_pfn(page); > + start_pfn = pfn & ~(pageblock_nr_pages - 1); > + end_pfn = start_pfn + pageblock_nr_pages - 1; > + > + start_page = pfn_to_page(start_pfn); > + end_page = pfn_to_page(end_pfn); > + > + for (cursor_page = start_page, pfn = start_pfn; cursor_page <= end_page; > + pfn++, cursor_page++) { > + struct zone *zone = page_zone(start_page); > + unsigned long flags; > + > + if (!pfn_valid_within(pfn)) > + continue; > + > + /* Do not deal with pageblocks that overlap zones */ > + if (page_zone(cursor_page) != zone) > + return false; > + > + if (!locked) > + spin_lock_irqsave(&zone->lock, flags); > + > + if (PageBuddy(cursor_page)) { > + int order = page_order(cursor_page); >-/* Returns true if the page is within a block suitable for migration to */ > -static bool suitable_migration_target(struct page *page) > + pfn += (1 << order) - 1; > + cursor_page += (1 << order) - 1; > + > + if (!locked) > + spin_unlock_irqrestore(&zone->lock, flags); > + continue; > + } else if (page_count(cursor_page) == 0 || > + PageLRU(cursor_page)) { > + if (!locked) > + spin_unlock_irqrestore(&zone->lock, flags); > + continue; > + } > + > + if (!locked) > + spin_unlock_irqrestore(&zone->lock, flags); spin_unlock in three spaces is ugly. How about adding a flag that holds the result of the function which you use as for loop condition and you set it to false inside an additional else clause? Eg.: bool result = true; for (...; result && cursor_page <= end_page; ...) { ... if (!pfn_valid_within(pfn)) continue; if (page_zone(cursor_page) != zone) return false; if (!locked) spin_lock_irqsave(...); if (PageBuddy(...)) { ... } else if (page_count(cursor_page) == 0 || PageLRU(cursor_page)) { ... } else { result = false; } if (!locked) spin_unlock_irqsave(...); } return result; > + return false; > + } > + > + return true; > +} How do you make sure that a page is not allocated while this runs? Or you just don't care? Not that even with zone lock, page may be allocated from pcp list on (another) CPU. -- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +------------------ooO--(_)--Ooo-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/