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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E13ACC531DF for ; Thu, 22 Aug 2024 07:20:34 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4WqF3P4RGfz2yR5; Thu, 22 Aug 2024 17:20:33 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=217.140.110.172 Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=dietmar.eggemann@arm.com; receiver=lists.ozlabs.org) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4WqF3N6PV8z2yKD for ; Thu, 22 Aug 2024 17:20:30 +1000 (AEST) 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 DF97ADA7; Thu, 22 Aug 2024 00:20:23 -0700 (PDT) Received: from [10.29.19.105] (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6521E3F58B; Thu, 22 Aug 2024 00:19:53 -0700 (PDT) Message-ID: <6580b2f6-ef95-4cd9-a573-ded7c8a4ef7d@arm.com> Date: Thu, 22 Aug 2024 09:19:30 +0200 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Post: List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 3/4] arm64: topology: Support SMT control on ACPI based system To: Yicong Yang Cc: catalin.marinas@arm.com, will@kernel.org, sudeep.holla@arm.com, tglx@linutronix.de, peterz@infradead.org, mpe@ellerman.id.au, linux-arm-kernel@lists.infradead.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, yangyicong@hisilicon.com, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, rafael@kernel.org, jonathan.cameron@huawei.com, prime.zeng@hisilicon.com, linuxarm@huawei.com, xuwei5@huawei.com, guohanjun@huawei.com References: <20240806085320.63514-1-yangyicong@huawei.com> <20240806085320.63514-4-yangyicong@huawei.com> <04ed0569-5026-9c4f-b09f-3e8798d5b551@huawei.com> From: Dietmar Eggemann Content-Language: en-US In-Reply-To: <04ed0569-5026-9c4f-b09f-3e8798d5b551@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 19/08/2024 09:03, Yicong Yang wrote: > On 2024/8/16 23:55, Dietmar Eggemann wrote: >> On 06/08/2024 10:53, Yicong Yang wrote: >>> From: Yicong Yang [...] >> So the xarray contains one element for each core_id with the information >> how often the core_id occurs? I assume you have to iterate over all >> possible CPUs since you don't know which logical CPUs belong to the same >> core_id. >> > > Each xarray element counts the thread number of a certain core id. so the logic is like below: > 1. if the "core id" entry doesn't exists, then we're accessing this core for the 1st time. create > one and make the thread number to 1 > 2. otherwise increment the thread number of "core id" this cpu belongs (PPTT already > told us which core this CPU belongs to). Update the max_smt_thread_num if necessary. > > Then we can know max_smt_thread_num by meanwhile iterating the PPTT table and > build the topology for all the possible CPUs. > > Otherwise we need to do a second scan for the max thread number after built the > topology. This way is implemented in v1 and it's complained about the overhead on large > scale systems since we need to loop the CPUs twice. OK. [...] >> Tested on ThunderX2: >> >> $ cat /proc/schedstat | head -6 | tail -4 | awk '{ print $1, $2 }' >> cpu0 0 >> domain0 00000000,00000000,00000000,00000000,00000001,00000001,00000001,00000001 >> ^ ^ ^ ^ >> domain1 00000000,00000000,00000000,00000000,ffffffff,ffffffff,ffffffff,ffffffff >> domain2 ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff,ffffffff >> >> detecting 'max_smt_thread_num = 4' correctly. >> > > Thanks for the testing. ok for a tag? Yes, please go ahead. [...]