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 CF921C43464 for ; Fri, 18 Sep 2020 02:17:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A4B7F238E6 for ; Fri, 18 Sep 2020 02:17:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729488AbgIRCRD (ORCPT ); Thu, 17 Sep 2020 22:17:03 -0400 Received: from out30-54.freemail.mail.aliyun.com ([115.124.30.54]:45774 "EHLO out30-54.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729470AbgIRCRA (ORCPT ); Thu, 17 Sep 2020 22:17:00 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R271e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04400;MF=richard.weiyang@linux.alibaba.com;NM=1;PH=DS;RN=17;SR=0;TI=SMTPD_---0U9GXwrg_1600395414; Received: from localhost(mailfrom:richard.weiyang@linux.alibaba.com fp:SMTPD_---0U9GXwrg_1600395414) by smtp.aliyun-inc.com(127.0.0.1); Fri, 18 Sep 2020 10:16:55 +0800 Date: Fri, 18 Sep 2020 10:16:54 +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: <20200918021654.GC54754@L-31X9LVDL-1304.local> Reply-To: Wei Yang 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> Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org 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 >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; Take another look into this part. Maybe we can move this check at top? For online_page case, currently we have following call flow: online_page online_pages_range shuffle_zone This means we would always shuffle the newly added pages. Maybe we don't need to do the shuffle when adding them to the free_list? > 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