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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 5C13FC4332E for ; Tue, 9 Feb 2021 21:54:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 247E464E56 for ; Tue, 9 Feb 2021 21:54:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233854AbhBIVyJ (ORCPT ); Tue, 9 Feb 2021 16:54:09 -0500 Received: from mx2.suse.de ([195.135.220.15]:52424 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233624AbhBITY6 (ORCPT ); Tue, 9 Feb 2021 14:24:58 -0500 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 2A1C0ADF0; Tue, 9 Feb 2021 19:03:34 +0000 (UTC) Date: Tue, 9 Feb 2021 20:03:32 +0100 From: Oscar Salvador To: David Hildenbrand Cc: Minchan Kim , Andrew Morton , linux-mm , LKML , Michal Hocko , Vlastimil Babka Subject: Re: [PATCH] mm: remove lru_add_drain_all in alloc_contig_range Message-ID: <20210209190332.GA3363@localhost.localdomain> References: <20210209175048.361638-1-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 09, 2021 at 07:17:59PM +0100, David Hildenbrand wrote: > On 09.02.21 18:50, Minchan Kim wrote: > > __alloc_contig_migrate_range already has lru_add_drain_all call > > via migrate_prep. It's necessary to move LRU taget pages into > > LRU list to be able to isolated. However, lru_add_drain_all call > > after __alloc_contig_migrate_range is called is pointless. > > > > This patch removes it. > > > > Signed-off-by: Minchan Kim > > --- > > mm/page_alloc.c | 2 -- > > 1 file changed, 2 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 6446778cbc6b..f8fbee73dd6d 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -8603,8 +8603,6 @@ int alloc_contig_range(unsigned long start, unsigned long end, > > * isolated thus they won't get removed from buddy. > > */ > > - lru_add_drain_all(); > > - > > order = 0; > > outer_start = start; > > while (!PageBuddy(pfn_to_page(outer_start))) { > > > > I was expecting some magical reason why this is still required but I am not > able to find a compelling one. Maybe this is really some historical > artifact. > > Let's see if other people know why this call here still exists. I also stumbled upon this while working on adding hugetlb support for alloc_acontig_range [1]. I have to confess I puzzled me a bit. I saw it going back to when the function was first introduced by commit 041d3a8cdc18dc375a128d90bbb753949a81b1fb Author: Michal Nazarewicz Date: Thu Dec 29 13:09:50 2011 +0100 mm: page_alloc: introduce alloc_contig_range() It does not make much sense to me. At this point our pages are free, so we do not care about LRU handling here. But I might be missing something. [1] https://lore.kernel.org/linux-mm/20210208103935.GA32103@linux/T/#md651fc6e73c656105179382f92f8b2d6073051d1 -- Oscar Salvador SUSE L3