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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 E3AEAC4363D for ; Fri, 25 Sep 2020 13:20:24 +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 6E17D2395C for ; Fri, 25 Sep 2020 13:20:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6E17D2395C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de 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 1kLndx-0006t7-4F; Fri, 25 Sep 2020 13:20:09 +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 1kLndw-0006qL-4c for xen-devel@lists.xenproject.org; Fri, 25 Sep 2020 13:20:08 +0000 X-Inumbo-ID: 74cf8291-c0e7-4cd5-9ca2-c8532cd015dc Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 74cf8291-c0e7-4cd5-9ca2-c8532cd015dc; Fri, 25 Sep 2020 13:20:06 +0000 (UTC) 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 EF96BB13B; Fri, 25 Sep 2020 13:20:01 +0000 (UTC) Date: Fri, 25 Sep 2020 15:19:48 +0200 From: Oscar Salvador 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 , 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: <20200925131948.GB3910@linux> 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> User-Agent: Mutt/1.10.1 (2018-07-13) 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: , 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 > 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 LGTM, the only thing is the shuffe_zone topic that Wei and Vlastimil rose. Feels a bit odd that takes precedence over something we explicitily demanded. With the comment Vlastimil suggested: Reviewed-by: Oscar Salvador -- Oscar Salvador SUSE L3