From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx134.postini.com [74.125.245.134]) by kanga.kvack.org (Postfix) with SMTP id B96766B0032 for ; Wed, 4 Sep 2013 04:24:28 -0400 (EDT) Received: from m1.gw.fujitsu.co.jp (unknown [10.0.50.71]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id 24E003EE0C1 for ; Wed, 4 Sep 2013 17:24:26 +0900 (JST) Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 1054345DE5D for ; Wed, 4 Sep 2013 17:24:26 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id D486845DE59 for ; Wed, 4 Sep 2013 17:24:25 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id C61CA1DB804B for ; Wed, 4 Sep 2013 17:24:25 +0900 (JST) Received: from g01jpfmpwyt03.exch.g01.fujitsu.local (g01jpfmpwyt03.exch.g01.fujitsu.local [10.128.193.57]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 661921DB8044 for ; Wed, 4 Sep 2013 17:24:25 +0900 (JST) Message-ID: <5226EE0F.5010906@jp.fujitsu.com> Date: Wed, 4 Sep 2013 17:23:43 +0900 From: Yasuaki Ishimatsu MIME-Version: 1.0 Subject: Re: [RFC PATCH v3 09/35] mm: Track the freepage migratetype of pages accurately References: <20130830131221.4947.99764.stgit@srivatsabhat.in.ibm.com> <20130830131635.4947.81565.stgit@srivatsabhat.in.ibm.com> <522583DE.709@jp.fujitsu.com> <5225A1A1.5010204@linux.vnet.ibm.com> In-Reply-To: <5225A1A1.5010204@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Srivatsa S. Bhat" Cc: akpm@linux-foundation.org, mgorman@suse.de, hannes@cmpxchg.org, tony.luck@intel.com, matthew.garrett@nebula.com, dave@sr71.net, riel@redhat.com, arjan@linux.intel.com, srinivas.pandruvada@linux.intel.com, willy@linux.intel.com, kamezawa.hiroyu@jp.fujitsu.com, lenb@kernel.org, rjw@sisk.pl, gargankita@gmail.com, paulmck@linux.vnet.ibm.com, svaidy@linux.vnet.ibm.com, andi@firstfloor.org, santosh.shilimkar@ti.com, kosaki.motohiro@gmail.com, linux-pm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org (2013/09/03 17:45), Srivatsa S. Bhat wrote: > On 09/03/2013 12:08 PM, Yasuaki Ishimatsu wrote: >> (2013/08/30 22:16), Srivatsa S. Bhat wrote: >>> Due to the region-wise ordering of the pages in the buddy allocator's >>> free lists, whenever we want to delete a free pageblock from a free list >>> (for ex: when moving blocks of pages from one list to the other), we need >>> to be able to tell the buddy allocator exactly which migratetype it >>> belongs >>> to. For that purpose, we can use the page's freepage migratetype >>> (which is >>> maintained in the page's ->index field). >>> >>> So, while splitting up higher order pages into smaller ones as part of >>> buddy >>> operations, keep the new head pages updated with the correct freepage >>> migratetype information (because we depend on tracking this info >>> accurately, >>> as outlined above). >>> >>> Signed-off-by: Srivatsa S. Bhat >>> --- >>> >>> mm/page_alloc.c | 7 +++++++ >>> 1 file changed, 7 insertions(+) >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index 398b62c..b4b1275 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -947,6 +947,13 @@ static inline void expand(struct zone *zone, >>> struct page *page, >>> add_to_freelist(&page[size], &area->free_list[migratetype]); >>> area->nr_free++; >>> set_page_order(&page[size], high); >>> + >>> + /* >>> + * Freepage migratetype is tracked using the index field of the >>> + * first page of the block. So we need to update the new first >>> + * page, when changing the page order. >>> + */ >>> + set_freepage_migratetype(&page[size], migratetype); >>> } >>> } >>> >>> >> >> It this patch a bug fix patch? >> If so, I want you to split the patch from the patch-set. >> > > No, its not a bug-fix. We need to take care of this only when using the > sorted-buddy design to maintain the freelists, which is introduced only in > this patchset. So mainline doesn't need this patch. > > In mainline, we can delete a page from a buddy freelist by simply calling > list_del() by passing a pointer to page->lru. It doesn't matter which freelist > the page was belonging to. However, in the sorted-buddy design introduced > in this patchset, we also need to know which particular freelist we are > deleting that page from, because apart from breaking the ->lru link from > the linked-list, we also need to update certain other things such as the > region->page_block pointer etc, which are part of that particular freelist. > Thus, it becomes essential to know which freelist we are deleting the page > from. And for that, we need this patch to maintain that information accurately > even during buddy operations such as splitting buddy pages in expand(). I may be wrong because I do not know this part clearly. Original code is here: --- static inline void expand(struct zone *zone, struct page *page, int low, int high, struct free_area *area, int migratetype) { ... list_add(&page[size].lru, &area->free_list[migratetype]); area->nr_free++; set_page_order(&page[size], high); --- It seems that migratietype of page[size] page is changed. So even if not applying your patch, I think migratetype of the page should be changed. thanks, Yasuaki Ishimatsu > > Regards, > Srivatsa S. Bhat > -- 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