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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED 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 353FDC43465 for ; Fri, 18 Sep 2020 02:08:33 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DB47623977 for ; Fri, 18 Sep 2020 02:08:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DB47623977 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kJ5ol-0004vV-Uu; Fri, 18 Sep 2020 02:08:07 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kJ5ok-0004vQ-Qz for xen-devel@lists.xenproject.org; Fri, 18 Sep 2020 02:08:06 +0000 X-Inumbo-ID: d5143593-6e4c-432e-9f70-35c52e90bc3d Received: from out30-57.freemail.mail.aliyun.com (unknown [115.124.30.57]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id d5143593-6e4c-432e-9f70-35c52e90bc3d; Fri, 18 Sep 2020 02:08:04 +0000 (UTC) X-Alimail-AntiSpam: AC=PASS; BC=-1|-1; BR=01201311R441e4; CH=green; DM=||false|; DS=||; FP=0|-1|-1|-1|0|-1|-1|-1; HT=e01e01424; MF=richard.weiyang@linux.alibaba.com; NM=1; PH=DS; RN=17; SR=0; TI=SMTPD_---0U9GoEaQ_1600394878; Received: from localhost(mailfrom:richard.weiyang@linux.alibaba.com fp:SMTPD_---0U9GoEaQ_1600394878) by smtp.aliyun-inc.com(127.0.0.1); Fri, 18 Sep 2020 10:07:58 +0800 Date: Fri, 18 Sep 2020 10:07:58 +0800 From: Wei Yang To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, 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 , Vlastimil Babka , Wei Yang , Oscar Salvador , Mike Rapoport , Scott Cheloha , Michael Ellerman Subject: Re: [PATCH RFC 2/4] mm/page_alloc: place pages to tail in __putback_isolated_page() Message-ID: <20200918020758.GB54754@L-31X9LVDL-1304.local> References: <20200916183411.64756-1-david@redhat.com> <20200916183411.64756-3-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200916183411.64756-3-david@redhat.com> X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Reply-To: Wei Yang Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On Wed, Sep 16, 2020 at 08:34:09PM +0200, David Hildenbrand wrote: >__putback_isolated_page() already documents that pages will be placed to >the tail of the freelist - this is, however, not the case for >"order >= MAX_ORDER - 2" (see buddy_merge_likely()) - which should be >the case for all existing users. > >This change affects two users: >- free page reporting >- page isolation, when undoing the isolation. > >This behavior is desireable for pages that haven't really been touched >lately, so exactly the two users that don't actually read/write page >content, but rather move untouched pages. > >The new behavior is especially desirable for memory onlining, where we >allow allocation of newly onlined pages via undo_isolate_page_range() >in online_pages(). Right now, we always place them to the head of the The code looks good, while I don't fully understand the log here. undo_isolate_page_range() is used in __offline_pages and alloc_contig_range. I don't connect them with online_pages(). Do I miss something? >free list, resulting in undesireable behavior: Assume we add >individual memory chunks via add_memory() and online them right away to >the NORMAL zone. We create a dependency chain of unmovable allocations >e.g., via the memmap. The memmap of the next chunk will be placed onto >previous chunks - if the last block cannot get offlined+removed, all >dependent ones cannot get offlined+removed. While this can already be >observed with individual DIMMs, it's more of an issue for virtio-mem >(and I suspect also ppc DLPAR). > >Note: If we observe a degradation due to the changed page isolation >behavior (which I doubt), we can always make this configurable by the >instance triggering undo of isolation (e.g., alloc_contig_range(), >memory onlining, memory offlining). > >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 >--- > mm/page_alloc.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > >diff --git a/mm/page_alloc.c b/mm/page_alloc.c >index 91cefb8157dd..bba9a0f60c70 100644 >--- a/mm/page_alloc.c >+++ b/mm/page_alloc.c >@@ -89,6 +89,12 @@ typedef int __bitwise fop_t; > */ > #define FOP_SKIP_REPORT_NOTIFY ((__force fop_t)BIT(0)) > >+/* >+ * Place the freed page to the tail of the freelist after buddy merging. Will >+ * get ignored with page shuffling enabled. >+ */ >+#define FOP_TO_TAIL ((__force fop_t)BIT(1)) >+ > /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */ > static DEFINE_MUTEX(pcp_batch_high_lock); > #define MIN_PERCPU_PAGELIST_FRACTION (8) >@@ -1040,6 +1046,8 @@ static inline void __free_one_page(struct page *page, unsigned long pfn, > > if (is_shuffle_order(order)) > to_tail = shuffle_pick_tail(); >+ else if (fop_flags & FOP_TO_TAIL) >+ to_tail = true; > else > to_tail = buddy_merge_likely(pfn, buddy_pfn, page, order); > >@@ -3289,7 +3297,7 @@ void __putback_isolated_page(struct page *page, unsigned int order, int mt) > > /* Return isolated page to tail of freelist. */ > __free_one_page(page, page_to_pfn(page), zone, order, mt, >- FOP_SKIP_REPORT_NOTIFY); >+ FOP_SKIP_REPORT_NOTIFY | FOP_TO_TAIL); > } > > /* >-- >2.26.2 -- Wei Yang Help you, Help me