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=-5.5 required=3.0 tests=MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 4F122C43441 for ; Wed, 10 Oct 2018 07:58:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0EC412064E for ; Wed, 10 Oct 2018 07:58:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0EC412064E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727011AbeJJPTs (ORCPT ); Wed, 10 Oct 2018 11:19:48 -0400 Received: from mx2.suse.de ([195.135.220.15]:35984 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726670AbeJJPTs (ORCPT ); Wed, 10 Oct 2018 11:19:48 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id BC818AC68; Wed, 10 Oct 2018 07:58:47 +0000 (UTC) Date: Wed, 10 Oct 2018 09:58:44 +0200 From: Michal Hocko To: Mike Rapoport Cc: linux-mm@kvack.org, Andrew Morton , Catalin Marinas , Chris Zankel , Geert Uytterhoeven , Guan Xuetao , Ingo Molnar , Matt Turner , Michael Ellerman , Michal Simek , Paul Burton , Richard Weinberger , Russell King , Thomas Gleixner , Tony Luck , linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org, linux-um@lists.infradead.org Subject: Re: [PATCH] memblock: stop using implicit alignement to SMP_CACHE_BYTES Message-ID: <20181010075844.GA5873@dhcp22.suse.cz> References: <1538687224-17535-1-git-send-email-rppt@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1538687224-17535-1-git-send-email-rppt@linux.vnet.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 05-10-18 00:07:04, Mike Rapoport wrote: > When a memblock allocation APIs are called with align = 0, the alignment is > implicitly set to SMP_CACHE_BYTES. I would add something like " Implicit alignment is done deep in the memblock allocator and it can come as a surprise. Not that such an alignment would be wrong even when used incorrectly but it is better to be explicit for the sake of clarity and the prinicple of the least surprise. " > Replace all such uses of memblock APIs with the 'align' parameter explicitly > set to SMP_CACHE_BYTES and stop implicit alignment assignment in the > memblock internal allocation functions. > > For the case when memblock APIs are used via helper functions, e.g. like > iommu_arena_new_node() in Alpha, the helper functions were detected with > Coccinelle's help and then manually examined and updated where appropriate. > > The direct memblock APIs users were updated using the semantic patch below: > > @@ > expression size, min_addr, max_addr, nid; > @@ > ( > | > - memblock_alloc_try_nid_raw(size, 0, min_addr, max_addr, nid) > + memblock_alloc_try_nid_raw(size, SMP_CACHE_BYTES, min_addr, max_addr, > nid) > | > - memblock_alloc_try_nid_nopanic(size, 0, min_addr, max_addr, nid) > + memblock_alloc_try_nid_nopanic(size, SMP_CACHE_BYTES, min_addr, max_addr, > nid) > | > - memblock_alloc_try_nid(size, 0, min_addr, max_addr, nid) > + memblock_alloc_try_nid(size, SMP_CACHE_BYTES, min_addr, max_addr, nid) > | > - memblock_alloc(size, 0) > + memblock_alloc(size, SMP_CACHE_BYTES) > | > - memblock_alloc_raw(size, 0) > + memblock_alloc_raw(size, SMP_CACHE_BYTES) > | > - memblock_alloc_from(size, 0, min_addr) > + memblock_alloc_from(size, SMP_CACHE_BYTES, min_addr) > | > - memblock_alloc_nopanic(size, 0) > + memblock_alloc_nopanic(size, SMP_CACHE_BYTES) > | > - memblock_alloc_low(size, 0) > + memblock_alloc_low(size, SMP_CACHE_BYTES) > | > - memblock_alloc_low_nopanic(size, 0) > + memblock_alloc_low_nopanic(size, SMP_CACHE_BYTES) > | > - memblock_alloc_from_nopanic(size, 0, min_addr) > + memblock_alloc_from_nopanic(size, SMP_CACHE_BYTES, min_addr) > | > - memblock_alloc_node(size, 0, nid) > + memblock_alloc_node(size, SMP_CACHE_BYTES, nid) > ) > > Suggested-by: Michal Hocko > Signed-off-by: Mike Rapoport I do agree that this is an improvement. I would also add WARN_ON_ONCE on 0 alignment to catch some left overs. If we ever grown a user which would explicitly require the zero alignment (I would be surprised) then we can remove the warning. Acked-by: Michal Hocko -- Michal Hocko SUSE Labs