From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx183.postini.com [74.125.245.183]) by kanga.kvack.org (Postfix) with SMTP id 1E33A6B005C for ; Mon, 4 Jun 2012 10:22:55 -0400 (EDT) Received: by eaan1 with SMTP id n1so1602196eaa.14 for ; Mon, 04 Jun 2012 07:22:53 -0700 (PDT) Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes 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: Quoted-Printable From: "Michal Nazarewicz" Message-ID: In-Reply-To: <201206041543.56917.b.zolnierkie@samsung.com> Sender: owner-linux-mm@kvack.org List-ID: 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 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 lo= cked) > +{ > + unsigned long pfn, start_pfn, end_pfn; > + struct page *start_page, *end_page, *cursor_page; > + > + pfn =3D page_to_pfn(page); > + start_pfn =3D pfn & ~(pageblock_nr_pages - 1); > + end_pfn =3D start_pfn + pageblock_nr_pages - 1; > + > + start_page =3D pfn_to_page(start_pfn); > + end_page =3D pfn_to_page(end_pfn); > + > + for (cursor_page =3D start_page, pfn =3D start_pfn; cursor_page <=3D= end_page; > + pfn++, cursor_page++) { > + struct zone *zone =3D 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) !=3D zone) > + return false; > + > + if (!locked) > + spin_lock_irqsave(&zone->lock, flags); > + > + if (PageBuddy(cursor_page)) { > + int order =3D page_order(cursor_page); >-/* Returns true if the page is within a block suitable for migration t= o */ > -static bool suitable_migration_target(struct page *page) > + pfn +=3D (1 << order) - 1; > + cursor_page +=3D (1 << order) - 1; > + > + if (!locked) > + spin_unlock_irqrestore(&zone->lock, flags); > + continue; > + } else if (page_count(cursor_page) =3D=3D 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 i= t to false inside an additional else clause? Eg.: bool result =3D true; for (...; result && cursor_page <=3D end_page; ...) { ... if (!pfn_valid_within(pfn)) continue; if (page_zone(cursor_page) !=3D zone) return false; if (!locked) spin_lock_irqsave(...); = if (PageBuddy(...)) { ... } else if (page_count(cursor_page) =3D=3D 0 || PageLRU(cursor_page)) { ... } else { result =3D 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 y= ou just don't care? Not that even with zone lock, page may be allocated from pc= p list on (another) CPU. -- = Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=3D./ `o ..o | Computer Science, Micha=C5=82 =E2=80=9Cmina86=E2=80=9D Nazarewicz= (o o) ooo +------------------ooO--(_)--Ooo-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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: email@kvack.org