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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 D850BE7718B for ; Mon, 23 Dec 2024 17:36:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Subject:CC:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=UlwxU9yU5UoX8moS94KBcUEK1tmdXrMY1Z1yZrD4Gl4=; b=f97MMjvJ0RR+OMHkQqD0mc+GBB C6uHLUAkESzA6O/Z/G0DZQm6nyevLsl7WO/rQZBSct2hxhru0YKhiPL5WzzVzDhCvdKK3LZZQ33Rs 8lcjNuRHBkGWNjpmW+TU2NyI8YvYZh5/en/McOKgMIUOfvQbZYqsIPhjwppw028vNYMk936d8NEmK 5B901YV0rQg7ATBb12JyDIlXAXDG3TeH6xEZxKy9RgEC0UCOTgctaXteQtu12NSGJOd4iI1OQUUe3 lMPhaOXag59azgz9thkolcT0d3HdiR5qMKDNycXUqd9konTI+JKp3m+2pfifBQ0KX/ltjZam+ROPB kO2braLw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tPmLk-0000000ATvD-2rDP; Mon, 23 Dec 2024 17:36:12 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tPlMz-0000000APJc-056q for linux-arm-kernel@lists.infradead.org; Mon, 23 Dec 2024 16:33:27 +0000 Received: from mail.maildlp.com (unknown [172.18.186.231]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4YH3V50KhNz6K75k; Tue, 24 Dec 2024 00:33:01 +0800 (CST) Received: from frapeml500008.china.huawei.com (unknown [7.182.85.71]) by mail.maildlp.com (Postfix) with ESMTPS id E7597140517; Tue, 24 Dec 2024 00:33:17 +0800 (CST) Received: from localhost (10.47.75.118) by frapeml500008.china.huawei.com (7.182.85.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Mon, 23 Dec 2024 17:33:16 +0100 Date: Mon, 23 Dec 2024 16:33:14 +0000 From: Jonathan Cameron To: Yicong Yang CC: , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v10 2/4] arch_topology: Support SMT control for OF based system Message-ID: <20241223163314.00006fed@huawei.com> In-Reply-To: <20241220075313.51502-3-yangyicong@huawei.com> References: <20241220075313.51502-1-yangyicong@huawei.com> <20241220075313.51502-3-yangyicong@huawei.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.75.118] X-ClientProxiedBy: lhrpeml100002.china.huawei.com (7.191.160.241) To frapeml500008.china.huawei.com (7.182.85.71) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241223_083325_357377_CA4C9CCD X-CRM114-Status: GOOD ( 26.64 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 20 Dec 2024 15:53:11 +0800 Yicong Yang wrote: > From: Yicong Yang > > On building the topology from the devicetree, we've already > gotten the SMT thread number of each core. Update the largest > SMT thread number and enable the SMT control by the end of > topology parsing. > > The core's SMT control provides two interface to the users [1]: > 1) enable/disable SMT by writing on/off > 2) enable/disable SMT by writing thread number 1/max_thread_number > > If a system have more than one SMT thread number the 2) may > not handle it well, since there're multiple thread numbers in the > system and 2) only accept 1/max_thread_number. So issue a warning > to notify the users if such system detected. > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/ABI/testing/sysfs-devices-system-cpu#n542 > Signed-off-by: Yicong Yang Hi Yicong, Apologies that I'm late to the game on this one. A few comments inline. Only important one is whether to bail out early on error from parse_cluster() Thanks, Jonathan > --- > drivers/base/arch_topology.c | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index 3ebe77566788..9e81060144c7 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -506,6 +507,10 @@ core_initcall(free_raw_capacity); > #endif > > #if defined(CONFIG_ARM64) || defined(CONFIG_RISCV) > + > +/* Maximum SMT thread number detected used to enable the SMT control */ > +static unsigned int max_smt_thread_num; > + > /* > * This function returns the logic cpu number of the node. > * There are basically three kinds of return values: > @@ -565,6 +570,17 @@ static int __init parse_core(struct device_node *core, int package_id, > i++; > } while (1); > > + /* > + * If max_smt_thread_num has been initialized and doesn't match > + * the thread number of this entry, then the system has > + * heterogeneous SMT topology. > + */ > + if (max_smt_thread_num && max_smt_thread_num != i) > + pr_warn_once("Heterogeneous SMT topology is partly supported by SMT control\n"); > + > + if (max_smt_thread_num < i) > + max_smt_thread_num = i; Maybe more self documenting if you use min()? I'm not sure... max_smt_thread_num = min(max_smt_thread_num, i); > + > cpu = get_cpu_for_node(core); > if (cpu >= 0) { > if (!leaf) { > @@ -677,6 +693,16 @@ static int __init parse_socket(struct device_node *socket) > if (!has_socket) > ret = parse_cluster(socket, 0, -1, 0); Is it appropriate to check ret before setting num threads? if (!has_socket) { ret = parse_cluster(socket, 0, -1, 0); if (ret) return ret; } ... return 0; > > + /* > + * Notify the CPU framework of the SMT support. Initialize the > + * max_smt_thread_num to 1 if no SMT support detected. A thread > + * number of 1 can be handled by the framework so we don't need > + * to check max_smt_thread_num to see we support SMT or not. > + */ > + if (!max_smt_thread_num) > + max_smt_thread_num = 1; > + > + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); Trivial but I'd put a blank line here. > return ret; > } >