From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752908Ab2FYBAz (ORCPT ); Sun, 24 Jun 2012 21:00:55 -0400 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:53535 "EHLO LGEMRELSE6Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751561Ab2FYBAy (ORCPT ); Sun, 24 Jun 2012 21:00:54 -0400 X-AuditID: 9c930179-b7befae000006417-9d-4fe7b843f272 Message-ID: <4FE7B861.6020906@kernel.org> Date: Mon, 25 Jun 2012 10:01:21 +0900 From: Minchan Kim User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 Newsgroups: gmane.linux.kernel.mm,gmane.linux.kernel To: Kamezawa Hiroyuki CC: undisclosed-recipients:"; KOSAKI Motohiro" , Aaditya Kumar , Mel Gorman , "linux-mm@kvack.org" , LKML Illegal-Object: Syntax error in CC: address found on vger.kernel.org: CC: undisclosed-recipients:;KOSAKI Motohiro ^-missing end of address Subject: Re: Accounting problem of MIGRATE_ISOLATED freed page References: <4FE169B1.7020600@kernel.org> <4FE16E80.9000306@gmail.com> <4FE18187.3050103@kernel.org> <4FE23069.5030702@gmail.com> <4FE26470.90401@kernel.org> <4FE27F15.8050102@kernel.org> <4FE2A937.6040701@kernel.org> <4FE2FCFB.4040808@jp.fujitsu.com> <4FE3C4E4.2050107@kernel.org> <4FE414A2.3000700@kernel.org> <4FE5482C.3010501@jp.fujitsu.com> In-Reply-To: <4FE5482C.3010501@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/23/2012 01:38 PM, Kamezawa Hiroyuki wrote: > (2012/06/22 15:45), Minchan Kim wrote: >> On 06/22/2012 10:05 AM, Minchan Kim wrote: >> >>> Second approach which is suggested by KOSAKI is what you mentioned. >>> But the concern about second approach is how to make sure matched >>> count increase/decrease of nr_isolated_areas. >>> I mean how to make sure nr_isolated_areas would be zero when >>> isolation is done. >>> Of course, we can investigate all of current caller and make sure >>> they don't make mistake >>> now. But it's very error-prone if we consider future's user. >>> So we might need test_set_pageblock_migratetype(page, MIGRATE_ISOLATE); >> >> >> It's an implementation about above approach. >> > > I like this approach. > > >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >> index bf3404e..3e9a9e1 100644 >> --- a/include/linux/mmzone.h >> +++ b/include/linux/mmzone.h >> @@ -474,6 +474,11 @@ struct zone { >> * rarely used fields: >> */ >> const char *name; >> + /* >> + * the number of MIGRATE_ISOLATE pageblock >> + * We need this for accurate free page counting. >> + */ >> + atomic_t nr_migrate_isolate; >> } ____cacheline_internodealigned_in_smp; > > Isn't this counter modified only under zone->lock ? AFAIUC, you want to add comment about it. It's no problem. :) Off-topic: As I look the code, I found this. Could you confirm this problem? CPU A CPU B start_isolate_page_range set_migratetype_isolate spin_lock_irqsave(zone->lock) free_hot_cold_page(Page A) migratetype = get_pageblock_migratetype(Page A); /* without zone->lock holding */ list_add_tail(&page->lru, &pcp->lists[migratetype]); /* Page A could return page into !MIGRATE_ISOLATE */ set_pageblock_migrate move_freepages_block drain_all_pages /* Page A could be in MIGRATE_MOVABLE of buddy. */ check_pages_isolated __test_page_isolated_in_pageblock if (PageBuddy(page A)) pfn += 1 << page_order(page A); /* Page A could be allocated */ __offline_isolated_pages BUG_ON(!PageBuddy(page A)); <- HIT! or offline the page is used by someone. > > >> >> typedef enum { >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 2c29b1c..6cb1f9f 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -219,6 +219,11 @@ EXPORT_SYMBOL(nr_online_nodes); >> >> int page_group_by_mobility_disabled __read_mostly; >> >> +/* >> + * NOTE: >> + * Don't use set_pageblock_migratetype(page, MIGRATE_ISOLATE) direclty. >> + * Instead, use {un}set_pageblock_isolate. >> + */ >> void set_pageblock_migratetype(struct page *page, int migratetype) >> { >> if (unlikely(page_group_by_mobility_disabled)) >> @@ -1622,6 +1627,28 @@ bool zone_watermark_ok(struct zone *z, int >> order, unsigned long mark, >> zone_page_state(z, >> NR_FREE_PAGES)); >> } > > I'm glad if this function can be static...Hm. With easy grep, I think it > can be... Yes. :) -- Kind regards, Minchan Kim From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx182.postini.com [74.125.245.182]) by kanga.kvack.org (Postfix) with SMTP id 1A9316B02F5 for ; Sun, 24 Jun 2012 21:00:55 -0400 (EDT) Message-ID: <4FE7B861.6020906@kernel.org> Date: Mon, 25 Jun 2012 10:01:21 +0900 From: Minchan Kim MIME-Version: 1.0 Subject: Re: Accounting problem of MIGRATE_ISOLATED freed page References: <4FE169B1.7020600@kernel.org> <4FE16E80.9000306@gmail.com> <4FE18187.3050103@kernel.org> <4FE23069.5030702@gmail.com> <4FE26470.90401@kernel.org> <4FE27F15.8050102@kernel.org> <4FE2A937.6040701@kernel.org> <4FE2FCFB.4040808@jp.fujitsu.com> <4FE3C4E4.2050107@kernel.org> <4FE414A2.3000700@kernel.org> <4FE5482C.3010501@jp.fujitsu.com> In-Reply-To: <4FE5482C.3010501@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Kamezawa Hiroyuki Cc: KOSAKI Motohiro , Aaditya Kumar , Mel Gorman , "linux-mm@kvack.org" , LKML On 06/23/2012 01:38 PM, Kamezawa Hiroyuki wrote: > (2012/06/22 15:45), Minchan Kim wrote: >> On 06/22/2012 10:05 AM, Minchan Kim wrote: >> >>> Second approach which is suggested by KOSAKI is what you mentioned. >>> But the concern about second approach is how to make sure matched >>> count increase/decrease of nr_isolated_areas. >>> I mean how to make sure nr_isolated_areas would be zero when >>> isolation is done. >>> Of course, we can investigate all of current caller and make sure >>> they don't make mistake >>> now. But it's very error-prone if we consider future's user. >>> So we might need test_set_pageblock_migratetype(page, MIGRATE_ISOLATE); >> >> >> It's an implementation about above approach. >> > > I like this approach. > > >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >> index bf3404e..3e9a9e1 100644 >> --- a/include/linux/mmzone.h >> +++ b/include/linux/mmzone.h >> @@ -474,6 +474,11 @@ struct zone { >> * rarely used fields: >> */ >> const char *name; >> + /* >> + * the number of MIGRATE_ISOLATE pageblock >> + * We need this for accurate free page counting. >> + */ >> + atomic_t nr_migrate_isolate; >> } ____cacheline_internodealigned_in_smp; > > Isn't this counter modified only under zone->lock ? AFAIUC, you want to add comment about it. It's no problem. :) Off-topic: As I look the code, I found this. Could you confirm this problem? CPU A CPU B start_isolate_page_range set_migratetype_isolate spin_lock_irqsave(zone->lock) free_hot_cold_page(Page A) migratetype = get_pageblock_migratetype(Page A); /* without zone->lock holding */ list_add_tail(&page->lru, &pcp->lists[migratetype]); /* Page A could return page into !MIGRATE_ISOLATE */ set_pageblock_migrate move_freepages_block drain_all_pages /* Page A could be in MIGRATE_MOVABLE of buddy. */ check_pages_isolated __test_page_isolated_in_pageblock if (PageBuddy(page A)) pfn += 1 << page_order(page A); /* Page A could be allocated */ __offline_isolated_pages BUG_ON(!PageBuddy(page A)); <- HIT! or offline the page is used by someone. > > >> >> typedef enum { >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 2c29b1c..6cb1f9f 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -219,6 +219,11 @@ EXPORT_SYMBOL(nr_online_nodes); >> >> int page_group_by_mobility_disabled __read_mostly; >> >> +/* >> + * NOTE: >> + * Don't use set_pageblock_migratetype(page, MIGRATE_ISOLATE) direclty. >> + * Instead, use {un}set_pageblock_isolate. >> + */ >> void set_pageblock_migratetype(struct page *page, int migratetype) >> { >> if (unlikely(page_group_by_mobility_disabled)) >> @@ -1622,6 +1627,28 @@ bool zone_watermark_ok(struct zone *z, int >> order, unsigned long mark, >> zone_page_state(z, >> NR_FREE_PAGES)); >> } > > I'm glad if this function can be static...Hm. With easy grep, I think it > can be... Yes. :) -- Kind regards, Minchan Kim -- 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/ . Don't email: email@kvack.org