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 241E1C3DA4A for ; Mon, 19 Aug 2024 08:26:44 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4WnQg63PGBz2xwc; Mon, 19 Aug 2024 18:26:42 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=45.249.212.191 Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=huawei.com (client-ip=45.249.212.191; helo=szxga05-in.huawei.com; envelope-from=yangyicong@huawei.com; receiver=lists.ozlabs.org) Received: from szxga05-in.huawei.com (szxga05-in.huawei.com [45.249.212.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4WnP8m5HxLz2xjv for ; Mon, 19 Aug 2024 17:18:44 +1000 (AEST) Received: from mail.maildlp.com (unknown [172.19.88.234]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4WnP2q02Xfz1j6dL; Mon, 19 Aug 2024 15:13:39 +0800 (CST) Received: from kwepemd200014.china.huawei.com (unknown [7.221.188.8]) by mail.maildlp.com (Postfix) with ESMTPS id 1176114022E; Mon, 19 Aug 2024 15:18:37 +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, 19 Aug 2024 15:18:36 +0800 CC: , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v5 2/4] arch_topology: Support SMT control for OF based system To: Dietmar Eggemann References: <20240806085320.63514-1-yangyicong@huawei.com> <20240806085320.63514-3-yangyicong@huawei.com> From: Yicong Yang Message-ID: <85c1501c-f398-bf96-f8b9-383fbb32d12f@huawei.com> Date: Mon, 19 Aug 2024 15:18:35 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Post: List-Subscribe: , , List-Unsubscribe: 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: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemd200014.china.huawei.com (7.221.188.8) On 2024/8/16 23:55, Dietmar Eggemann wrote: > On 06/08/2024 10:53, 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 to enable the SMT control. > > Do we have SMT Device Tree (DT) systems out there? But you right that DT > at least supports SMT. > My system's based on ACPI. For DT part it's emulated and tested on the QEMU VM. >> Signed-off-by: Yicong Yang >> --- >> drivers/base/arch_topology.c | 13 +++++++++++++ >> 1 file changed, 13 insertions(+) >> >> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c >> index 75fcb75d5515..95513abd664f 100644 >> --- a/drivers/base/arch_topology.c >> +++ b/drivers/base/arch_topology.c >> @@ -11,6 +11,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> #include >> @@ -531,6 +532,16 @@ static int __init get_cpu_for_node(struct device_node *node) >> return cpu; >> } >> >> +static void __init update_smt_num_threads(unsigned int num_threads) >> +{ >> + static unsigned int max_smt_thread_num = 1; >> + >> + if (num_threads > max_smt_thread_num) { >> + max_smt_thread_num = num_threads; >> + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); >> + } > > This could theoretically (unlikely though) call > cpu_smt_set_num_threads() multiple times (on heterogeneous systems with > different numbers of SMT threads). Yes indeed. Was doing this purposely since I think this doing nothing unexpectedly but only update the max threads recorded in the framework. >> +} >> + >> static int __init parse_core(struct device_node *core, int package_id, >> int cluster_id, int core_id) >> { >> @@ -561,6 +572,8 @@ static int __init parse_core(struct device_node *core, int package_id, >> i++; >> } while (1); >> >> + update_smt_num_threads(i); >> + >> cpu = get_cpu_for_node(core); >> if (cpu >= 0) { >> if (!leaf) { > > Why not simply do this: > > -->8-- > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index 75fcb75d5515..806537419715 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -30,6 +30,7 @@ static struct cpumask scale_freq_counters_mask; > static bool scale_freq_invariant; > DEFINE_PER_CPU(unsigned long, capacity_freq_ref) = 1; > EXPORT_PER_CPU_SYMBOL_GPL(capacity_freq_ref); > +static unsigned int max_smt_thread_num = 1; > This fine with me and this avoid calling cpu_smt_set_num_threads() multiple times. We can switch to this implementation. Thanks. > static bool supports_scale_freq_counters(const struct cpumask *cpus) > { > @@ -577,6 +578,9 @@ static int __init parse_core(struct device_node *core, int package_id, > return -EINVAL; > } > > + if (max_smt_thread_num < i) > + max_smt_thread_num = i; > + > return 0; > } > > @@ -673,6 +677,9 @@ static int __init parse_socket(struct device_node *socket) > if (!has_socket) > ret = parse_cluster(socket, 0, -1, 0); > > + if (max_smt_thread_num > 1) > + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); > + > return ret; > } > > > . >