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 8C65AC282D1 for ; Mon, 3 Mar 2025 14:43:05 +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:In-Reply-To:MIME-Version:Date:Message-ID:From:References:To: Subject:CC:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=PyFmoPLxI3Bt/mKH+4GGVhiV4FqREb8L/Cp19+HR3OY=; b=zY0fx5ahZAdMhh093+WV/suM/k I0JISRklZzzE0HHi6GPjMJRUm5OeZEnWvVRFAPJtB96LN1dDydiXNcDCghQgd88Zj2gXGvLxuA094 duLW+QjP5wKOvqPSu1xMF1lDBfBYvZVHrwrRT6QHc+dey3VBB6bOAmhsJ+Bz42Q3fVW7zD7MiI4dg eZOXBbUEb7CtgWp1agy7yMnPt/r0JdoZNDkCtpPPS+oZUGNcVTfuul+071WI9FEQ9kUosm7xNVjhJ 7FV7AKSNmJZSgC9w64cOEYm5+NVLBttL2EFR841zQ4hzxRbmTHxWk8LUM56vrw1zOWSn2o2npELaL pPpue44Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tp70N-000000019QX-3Ihr; Mon, 03 Mar 2025 14:42:51 +0000 Received: from szxga01-in.huawei.com ([45.249.212.187]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tp6ym-00000001944-39We for linux-arm-kernel@lists.infradead.org; Mon, 03 Mar 2025 14:41:13 +0000 Received: from mail.maildlp.com (unknown [172.19.88.105]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Z61Zl13Y8zwW49; Mon, 3 Mar 2025 22:35:59 +0800 (CST) Received: from kwepemd200014.china.huawei.com (unknown [7.221.188.8]) by mail.maildlp.com (Postfix) with ESMTPS id 3682E1402C8; Mon, 3 Mar 2025 22:40:51 +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; Mon, 3 Mar 2025 22:40:50 +0800 CC: , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v11 3/4] arm64: topology: Support SMT control on ACPI based system To: Sudeep Holla , Pierre Gondois References: <20250218141018.18082-1-yangyicong@huawei.com> <20250218141018.18082-4-yangyicong@huawei.com> <336e9c4e-cd9c-4449-ba7b-60ee8774115d@arm.com> <20250228190641.q23vd53aaw42tcdi@bogus> From: Yicong Yang Message-ID: <32e572d6-dedd-d8a3-13be-6de02303a64d@huawei.com> Date: Mon, 3 Mar 2025 22:40:49 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.121.177] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemd200014.china.huawei.com (7.221.188.8) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250303_064113_003514_2E81B3CB X-CRM114-Status: GOOD ( 15.68 ) 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 2025/3/3 19:16, Sudeep Holla wrote: > On Mon, Mar 03, 2025 at 10:56:12AM +0100, Pierre Gondois wrote: >> On 2/28/25 20:06, Sudeep Holla wrote: >>>>> >>>>> Ditto as previous patch, can get rid if it is default 1. >>>>> >>>> >>>> On non-SMT platforms, not calling cpu_smt_set_num_threads() leaves >>>> cpu_smt_num_threads uninitialized to UINT_MAX: >>>> >>>> smt/active:0 >>>> smt/control:-1 >>>> >>>> If cpu_smt_set_num_threads() is called: >>>> active:0 >>>> control:notsupported >>>> >>>> So it might be slightly better to still initialize max_smt_thread_num. >>>> >>> >>> Sure, what I meant is to have max_smt_thread_num set to 1 by default is >>> that is what needed anyways and the above code does that now. >>> >>> Why not start with initialised to 1 instead ? >>> Of course some current logic needs to change around testing it for zero. >>> >> >> I think there would still be a way to check against the default value. >> If we have: >> unsigned int max_smt_thread_num = 1; >> >> then on a platform with 2 threads, the detection condition would trigger: >> xa_for_each(&hetero_cpu, hetero_id, entry) { >> if (entry->thread_num != max_smt_thread_num && max_smt_thread_num) <---- (entry->thread_num=2) and (max_smt_thread_num=1) >> pr_warn_once("Heterogeneous SMT topology is partly >> supported by SMT control\n"); >> >> so we would need an additional variable: >> bool is_initialized = false; > > Sure, we could do that or skip the check if max_smt_thread_num == 1 ? > > I mean > if (entry->thread_num != max_smt_thread_num && max_smt_thread_num != 1) > this will work for me. will launch some tests. Thanks.