From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9FE07146A71 for ; Thu, 26 Dec 2024 11:50:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735213850; cv=none; b=Om49PpMRTi9/nsYU/3hKSAg8ZSwmB1vhc7UvrNze7kgRiaEYTKKa2T34HgETL7ofBXg/GOd55eWMbrrffD7TI/hcchfgltHKmmw2KhaWJk4TkgC8iL+RBo0Z1AwB411Q3tgFeA4kW0vf5RMSLWAkGJXaZKwsTgwslIIGYKJ4aDs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735213850; c=relaxed/simple; bh=wqcj7EJoFky3NEqMWSUbniS9QnFelHAU9z6qhoBA0ws=; h=CC:Subject:To:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=aO3KJDURSEdKHxbV4qLex/pvCax7ruxQDdR4oAo5VmqdP1xelfaYgIuHLTqLbQTU/xsD4Dj1NPAMavzp7L1Qb2ub57k7xywv3pQGtOpve/jev1Wb3FruT0bqy9ykrvTm9l0QCKRyyjEwyh8gdjaVEU+pHbRkR5I4Zcj/GhN6Azc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.48]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4YJn2X6DSLzRk9r; Thu, 26 Dec 2024 19:48:36 +0800 (CST) Received: from kwepemd200014.china.huawei.com (unknown [7.221.188.8]) by mail.maildlp.com (Postfix) with ESMTPS id 2C4AD1802D2; Thu, 26 Dec 2024 19:50:38 +0800 (CST) Received: from [10.67.121.177] (10.67.121.177) by kwepemd200014.china.huawei.com (7.221.188.8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.34; Thu, 26 Dec 2024 19:50:37 +0800 CC: , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v10 0/4] Support SMT control on arm64 To: Shrikanth Hegde References: <20241220075313.51502-1-yangyicong@huawei.com> From: Yicong Yang Message-ID: Date: Thu, 26 Dec 2024 19:50:36 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemd200014.china.huawei.com (7.221.188.8) On 2024/12/26 17:23, Shrikanth Hegde wrote: > > > On 12/20/24 13:23, Yicong Yang wrote: >> From: Yicong Yang >> >> The core CPU control framework supports runtime SMT control which >> is not yet supported on arm64. Besides the general vulnerabilities >> concerns we want this runtime control on our arm64 server for: >> >> - better single CPU performance in some cases >> - saving overall power consumption >> > > EAS is disabled when SMT is present. > I am curious to know how power saving happens here. EAS shouldn't work on non-asymmetic systems, so it's not the case here. System wide power consumption comes down from the CPU offlining here. Thanks. > >> This patchset implements it in the following aspects: >> >> - Provides a default topology_is_primary_thread() >> - support retrieve SMT thread number on OF based system >> - support retrieve SMT thread number on ACPI based system >> - select HOTPLUG_SMT for arm64 >> >> Tests has been done on our ACPI based arm64 server and on ACPI/OF\ >> based QEMU VMs. >> > .