From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6EA3CC4727E for ; Thu, 24 Sep 2020 11:13:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 347CA239D4 for ; Thu, 24 Sep 2020 11:13:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726483AbgIXLNc (ORCPT ); Thu, 24 Sep 2020 07:13:32 -0400 Received: from mx2.suse.de ([195.135.220.15]:53392 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726415AbgIXLNb (ORCPT ); Thu, 24 Sep 2020 07:13:31 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4A408AC85; Thu, 24 Sep 2020 11:13:30 +0000 (UTC) Subject: Re: [PATCH RFC 3/4] mm/page_alloc: always move pages to the tail of the freelist in unset_migratetype_isolate() To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org, linux-acpi@vger.kernel.org, Andrew Morton , Alexander Duyck , Mel Gorman , Michal Hocko , Dave Hansen , Wei Yang , Oscar Salvador , Mike Rapoport , Scott Cheloha , Michael Ellerman References: <20200916183411.64756-1-david@redhat.com> <20200916183411.64756-4-david@redhat.com> From: Vlastimil Babka Message-ID: <9c6cc094-b02a-ac6c-e1ca-370ce7257881@suse.cz> Date: Thu, 24 Sep 2020 13:13:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200916183411.64756-4-david@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On 9/16/20 8:34 PM, David Hildenbrand wrote: > Page isolation doesn't actually touch the pages, it simply isolates > pageblocks and moves all free pages to the MIGRATE_ISOLATE freelist. > > We already place pages to the tail of the freelists when undoing > isolation via __putback_isolated_page(), let's do it in any case > (e.g., if order == pageblock_order) and document the behavior. > > This change results in all pages getting onlined via online_pages() to > be placed to the tail of the freelist. > > Cc: Andrew Morton > Cc: Alexander Duyck > Cc: Mel Gorman > Cc: Michal Hocko > Cc: Dave Hansen > Cc: Vlastimil Babka > Cc: Wei Yang > Cc: Oscar Salvador > Cc: Mike Rapoport > Cc: Scott Cheloha > Cc: Michael Ellerman > Signed-off-by: David Hildenbrand > --- > include/linux/page-isolation.h | 2 ++ > mm/page_alloc.c | 36 +++++++++++++++++++++++++++++----- > mm/page_isolation.c | 8 ++++++-- > 3 files changed, 39 insertions(+), 7 deletions(-) > > diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h > index 572458016331..a36be2cf4dbb 100644 > --- a/include/linux/page-isolation.h > +++ b/include/linux/page-isolation.h > @@ -38,6 +38,8 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, > void set_pageblock_migratetype(struct page *page, int migratetype); > int move_freepages_block(struct zone *zone, struct page *page, > int migratetype, int *num_movable); > +int move_freepages_block_tail(struct zone *zone, struct page *page, > + int migratetype); > > /* > * Changes migrate type in [start_pfn, end_pfn) to be MIGRATE_ISOLATE. > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index bba9a0f60c70..75b0f49b4022 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -899,6 +899,15 @@ static inline void move_to_free_list(struct page *page, struct zone *zone, > list_move(&page->lru, &area->free_list[migratetype]); > } > > +/* Used for pages which are on another list */ > +static inline void move_to_free_list_tail(struct page *page, struct zone *zone, > + unsigned int order, int migratetype) > +{ > + struct free_area *area = &zone->free_area[order]; > + > + list_move_tail(&page->lru, &area->free_list[migratetype]); > +} There are just 3 callers of move_to_free_list() before this patch, I would just add the to_tail parameter there instead of new wrapper. For callers with constant parameter, the inline will eliminate it anyway. > static inline void del_page_from_free_list(struct page *page, struct zone *zone, > unsigned int order) > { > @@ -2323,7 +2332,7 @@ static inline struct page *__rmqueue_cma_fallback(struct zone *zone, > */ > static int move_freepages(struct zone *zone, > struct page *start_page, struct page *end_page, > - int migratetype, int *num_movable) > + int migratetype, int *num_movable, bool to_tail) > { > struct page *page; > unsigned int order; > @@ -2354,7 +2363,10 @@ static int move_freepages(struct zone *zone, > VM_BUG_ON_PAGE(page_zone(page) != zone, page); > > order = page_order(page); > - move_to_free_list(page, zone, order, migratetype); > + if (to_tail) > + move_to_free_list_tail(page, zone, order, migratetype); > + else > + move_to_free_list(page, zone, order, migratetype); > page += 1 << order; > pages_moved += 1 << order; > } > @@ -2362,8 +2374,9 @@ static int move_freepages(struct zone *zone, > return pages_moved; > } > > -int move_freepages_block(struct zone *zone, struct page *page, > - int migratetype, int *num_movable) > +static int __move_freepages_block(struct zone *zone, struct page *page, > + int migratetype, int *num_movable, > + bool to_tail) > { > unsigned long start_pfn, end_pfn; > struct page *start_page, *end_page; > @@ -2384,7 +2397,20 @@ int move_freepages_block(struct zone *zone, struct page *page, > return 0; > > return move_freepages(zone, start_page, end_page, migratetype, > - num_movable); > + num_movable, to_tail); > +} > + > +int move_freepages_block(struct zone *zone, struct page *page, > + int migratetype, int *num_movable) > +{ > + return __move_freepages_block(zone, page, migratetype, num_movable, > + false); > +} > + > +int move_freepages_block_tail(struct zone *zone, struct page *page, > + int migratetype) > +{ > + return __move_freepages_block(zone, page, migratetype, NULL, true); > } Likewise, just 5 callers of move_freepages_block(), all in the files you're already changing, so no need for this wrappers IMHO. Thanks, Vlastimil > static void change_pageblock_range(struct page *pageblock_page, > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index abfe26ad59fd..84aa1d14751d 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -83,7 +83,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) > * Because freepage with more than pageblock_order on isolated > * pageblock is restricted to merge due to freepage counting problem, > * it is possible that there is free buddy page. > - * move_freepages_block() doesn't care of merge so we need other > + * move_freepages_block*() don't care about merging, so we need another > * approach in order to merge them. Isolation and free will make > * these pages to be merged. > */ > @@ -106,9 +106,13 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) > * If we isolate freepage with more than pageblock_order, there > * should be no freepage in the range, so we could avoid costly > * pageblock scanning for freepage moving. > + * > + * We didn't actually touch any of the isolated pages, so place them > + * to the tail of the freelists. This is especially relevant during > + * memory onlining. > */ > if (!isolated_page) { > - nr_pages = move_freepages_block(zone, page, migratetype, NULL); > + nr_pages = move_freepages_block_tail(zone, page, migratetype); > __mod_zone_freepage_state(zone, nr_pages, migratetype); > } > set_pageblock_migratetype(page, migratetype); >