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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, 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 0FC8EC4363D for ; Wed, 21 Oct 2020 04:13:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5E06221FC for ; Wed, 21 Oct 2020 04:13:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406960AbgJUENx (ORCPT ); Wed, 21 Oct 2020 00:13:53 -0400 Received: from foss.arm.com ([217.140.110.172]:58556 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404232AbgJUENx (ORCPT ); Wed, 21 Oct 2020 00:13:53 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 66AE01FB; Tue, 20 Oct 2020 21:13:52 -0700 (PDT) Received: from [192.168.0.130] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 85AA13F66E; Tue, 20 Oct 2020 21:13:50 -0700 (PDT) Subject: Re: [PATCH] arm64: NUMA: Kconfig: Increase max number of nodes To: Valentin Schneider , Vanshidhar Konda Cc: linux-arm-kernel@lists.infradead.org, patches@amperecomputing.com, linux-kernel@vger.kernel.org References: <20201020173409.1266576-1-vanshikonda@os.amperecomputing.com> From: Anshuman Khandual Message-ID: <9e14c0d3-9204-fb32-31db-5b3f98639cba@arm.com> Date: Wed, 21 Oct 2020 09:43:21 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/20/2020 11:39 PM, Valentin Schneider wrote: > > Hi, > > Nit on the subject: this only increases the default, the max is still 2¹⁰. Agreed. > > On 20/10/20 18:34, Vanshidhar Konda wrote: >> The current arm64 max NUMA nodes default to 4. Today's arm64 systems can >> reach or exceed 16. Increase the number to 64 (matching x86_64). >> >> Signed-off-by: Vanshidhar Konda >> --- >> arch/arm64/Kconfig | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index 893130ce1626..3e69d3c981be 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -980,7 +980,7 @@ config NUMA >> config NODES_SHIFT >> int "Maximum NUMA Nodes (as a power of 2)" >> range 1 10 >> - default "2" >> + default "6" > > This leads to more statically allocated memory for things like node to CPU > maps (see uses of MAX_NUMNODES), but that shouldn't be too much of an > issue. The smaller systems should not be required to waste those memory in a default case, unless there is a real and available larger system with those increased nodes. > > AIUI this also directly correlates to how many more page->flags bits are > required: are we sure the max 10 works on any aarch64 platform? I'm We will have to test that. Besides 256 (2 ^ 8) is the first threshold to be crossed here. > genuinely asking here, given that I'm mostly a stranger to the mm > world. The default should be something we're somewhat confident works > everywhere. Agreed. Do we really need to match X86 right now ? Do we really have systems that has 64 nodes ? We should not increase the default node value and then try to solve some new problems, when there might not be any system which could even use that. I would suggest increase NODES_SHIFT value upto as required by a real and available system. > >> depends on NEED_MULTIPLE_NODES >> help >> Specify the maximum number of NUMA Nodes available on the target >