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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 E5B0CC4363A for ; Mon, 5 Oct 2020 08:29:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B84F02078E for ; Mon, 5 Oct 2020 08:29:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725891AbgJEI3E (ORCPT ); Mon, 5 Oct 2020 04:29:04 -0400 Received: from outbound-smtp30.blacknight.com ([81.17.249.61]:44485 "EHLO outbound-smtp30.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725880AbgJEI3E (ORCPT ); Mon, 5 Oct 2020 04:29:04 -0400 X-Greylist: delayed 492 seconds by postgrey-1.27 at vger.kernel.org; Mon, 05 Oct 2020 04:29:03 EDT Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp30.blacknight.com (Postfix) with ESMTPS id 26ED518068 for ; Mon, 5 Oct 2020 09:20:51 +0100 (IST) Received: (qmail 11945 invoked from network); 5 Oct 2020 08:20:50 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.22.4]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 5 Oct 2020 08:20:50 -0000 Date: Mon, 5 Oct 2020 09:20:49 +0100 From: Mel Gorman To: Michal Hocko Cc: David Hildenbrand , Vlastimil Babka , 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 , Oscar Salvador , Alexander Duyck , Dave Hansen , Wei Yang , Mike Rapoport , Scott Cheloha , Michael Ellerman Subject: Re: [PATCH v1 3/5] mm/page_alloc: always move pages to the tail of the freelist in unset_migratetype_isolate() Message-ID: <20201005082049.GI3227@techsingularity.net> References: <20200928182110.7050-1-david@redhat.com> <20200928182110.7050-4-david@redhat.com> <20201002132404.GI4555@dhcp22.suse.cz> <20201005065648.GO4555@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20201005065648.GO4555@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org Archived-At: List-Archive: List-Post: On Mon, Oct 05, 2020 at 08:56:48AM +0200, Michal Hocko wrote: > On Fri 02-10-20 17:20:09, David Hildenbrand wrote: > > On 02.10.20 15:24, Michal Hocko wrote: > > > On Mon 28-09-20 20:21:08, 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. > > >> > > >> Add a "to_tail" parameter to move_freepages_block() but introduce a > > >> a new move_to_free_list_tail() - similar to add_to_free_list_tail(). > > >> > > >> This change results in all pages getting onlined via online_pages() to > > >> be placed to the tail of the freelist. > > > > > > Is there anything preventing to do this unconditionally? Or in other > > > words is any of the existing callers of move_freepages_block benefiting > > > from adding to the head? > > > > 1. mm/page_isolation.c:set_migratetype_isolate() > > > > We move stuff to the MIGRATE_ISOLATE list, we don't care about the order > > there. > > > > 2. steal_suitable_fallback(): > > > > I don't think we care too much about the order when already stealing > > pageblocks ... and the freelist is empty I guess? > > > > 3. reserve_highatomic_pageblock()/unreserve_highatomic_pageblock() > > > > Not sure if we really care. > > Honestly, I have no idea. I can imagine that some atomic high order > workloads (e.g. in net) might benefit from cache line hot pages but I am > not sure this is really observable. The highatomic reserve is more concerned that about the allocation succeeding than it is about cache hotness. -- Mel Gorman SUSE Labs