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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 77E89C43331 for ; Mon, 30 Mar 2020 10:44:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 46CA02072E for ; Mon, 30 Mar 2020 10:44:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="T4Zeag7t" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729351AbgC3KoK (ORCPT ); Mon, 30 Mar 2020 06:44:10 -0400 Received: from us-smtp-delivery-74.mimecast.com ([63.128.21.74]:22306 "EHLO us-smtp-delivery-74.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729315AbgC3KoJ (ORCPT ); Mon, 30 Mar 2020 06:44:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585565048; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ubZwCgodS3U5y1iwpfdeziXkCswHWi54UlMSk9s9wOI=; b=T4Zeag7tmUxfTXyYIjCJ/5P8VzRW8l3y8bZNEqeKEkr8DYIS6MCfdXTm9DuhsYEkR8R1c1 O32ybm4pwkUjNnlRceLiF4O4jQti5Xcec253g7LbtGzuYOXovUdoK7KugLO1Lf5zZXHaTc Ho1kFUTo+fTjxrBLACALgGUpaX2z0ms= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-294-RWReSoGTPOenn7_wlRjk4w-1; Mon, 30 Mar 2020 06:44:04 -0400 X-MC-Unique: RWReSoGTPOenn7_wlRjk4w-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DE63913F7; Mon, 30 Mar 2020 10:44:00 +0000 (UTC) Received: from localhost (ovpn-12-192.pek2.redhat.com [10.72.12.192]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 20B5E19757; Mon, 30 Mar 2020 10:43:59 +0000 (UTC) Date: Mon, 30 Mar 2020 18:43:56 +0800 From: Baoquan He To: Mike Rapoport Cc: Michal Hocko , Hoan Tran , Catalin Marinas , Will Deacon , Andrew Morton , Vlastimil Babka , Oscar Salvador , Pavel Tatashin , Alexander Duyck , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , "David S. Miller" , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , "open list:MEMORY MANAGEMENT" , linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, lho@amperecomputing.com, mmorana@amperecomputing.com Subject: Re: [PATCH v3 0/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA Message-ID: <20200330104356.GD6352@MiWiFi-R3L-srv> References: <1585420282-25630-1-git-send-email-Hoan@os.amperecomputing.com> <20200330074246.GA14243@dhcp22.suse.cz> <20200330092127.GB30942@linux.ibm.com> <20200330095843.GF14243@dhcp22.suse.cz> <20200330102619.GC30942@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200330102619.GC30942@linux.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/30/20 at 01:26pm, Mike Rapoport wrote: > On Mon, Mar 30, 2020 at 11:58:43AM +0200, Michal Hocko wrote: > > On Mon 30-03-20 12:21:27, Mike Rapoport wrote: > > > On Mon, Mar 30, 2020 at 09:42:46AM +0200, Michal Hocko wrote: > > > > On Sat 28-03-20 11:31:17, Hoan Tran wrote: > > > > > In NUMA layout which nodes have memory ranges that span across other nodes, > > > > > the mm driver can detect the memory node id incorrectly. > > > > > > > > > > For example, with layout below > > > > > Node 0 address: 0000 xxxx 0000 xxxx > > > > > Node 1 address: xxxx 1111 xxxx 1111 > > > > > > > > > > Note: > > > > > - Memory from low to high > > > > > - 0/1: Node id > > > > > - x: Invalid memory of a node > > > > > > > > > > When mm probes the memory map, without CONFIG_NODES_SPAN_OTHER_NODES > > > > > config, mm only checks the memory validity but not the node id. > > > > > Because of that, Node 1 also detects the memory from node 0 as below > > > > > when it scans from the start address to the end address of node 1. > > > > > > > > > > Node 0 address: 0000 xxxx xxxx xxxx > > > > > Node 1 address: xxxx 1111 1111 1111 > > > > > > > > > > This layout could occur on any architecture. Most of them enables > > > > > this config by default with CONFIG_NUMA. This patch, by default, enables > > > > > CONFIG_NODES_SPAN_OTHER_NODES or uses early_pfn_in_nid() for NUMA. > > > > > > > > I am not opposed to this at all. It reduces the config space and that is > > > > a good thing on its own. The history has shown that meory layout might > > > > be really wild wrt NUMA. The config is only used for early_pfn_in_nid > > > > which is clearly an overkill. > > > > > > > > Your description doesn't really explain why this is safe though. The > > > > history of this config is somehow messy, though. Mike has tried > > > > to remove it a94b3ab7eab4 ("[PATCH] mm: remove arch independent > > > > NODES_SPAN_OTHER_NODES") just to be reintroduced by 7516795739bd > > > > ("[PATCH] Reintroduce NODES_SPAN_OTHER_NODES for powerpc") without any > > > > reasoning what so ever. This doesn't make it really easy see whether > > > > reasons for reintroduction are still there. Maybe there are some subtle > > > > dependencies. I do not see any TBH but that might be burried deep in an > > > > arch specific code. > > > > > > Well, back then early_pfn_in_nid() was arch-dependant, today everyone > > > except ia64 rely on HAVE_MEMBLOCK_NODE_MAP. > > > > What would it take to make ia64 use HAVE_MEMBLOCK_NODE_MAP? I would > > really love to see that thing go away. It is causing problems when > > people try to use memblock api. > > Sorry, my bad, ia64 does not have NODES_SPAN_OTHER_NODES, but it does have > HAVE_MEMBLOCK_NODE_MAP. > > I remember I've tried killing HAVE_MEMBLOCK_NODE_MAP, but I've run into > some problems and then I've got distracted. I too would like to have > HAVE_MEMBLOCK_NODE_MAP go away, maybe I'll take another look at it. > > > > So, if the memblock node map > > > is correct, that using CONFIG_NUMA instead of CONFIG_NODES_SPAN_OTHER_NODES > > > would only mean that early_pfn_in_nid() will cost several cycles more on > > > architectures that didn't select CONFIG_NODES_SPAN_OTHER_NODES (i.e. arm64 > > > and sh). > > > > Do we have any idea on how much of an overhead that is? Because this is > > per each pfn so it can accumulate a lot! > > It's O(log(N)) where N is the amount of the memory banks (ie. memblock.memory.cnt) This is for the Node id searching. But early_pfn_in_nid() is calling for each pfn, this is the big one, I think. Otherwise, it may be optimized as no-op. > > > > Agian, ia64 is an exception here. > > > > Thanks for the clarification! > > -- > > Michal Hocko > > SUSE Labs > > -- > Sincerely yours, > Mike. > >