From patchwork Thu Feb 23 19:11:35 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Usama Arif X-Patchwork-Id: 13150687 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2763C636D6 for ; Thu, 23 Feb 2023 19:12:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232096AbjBWTMz (ORCPT ); Thu, 23 Feb 2023 14:12:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60030 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231889AbjBWTMu (ORCPT ); Thu, 23 Feb 2023 14:12:50 -0500 Received: from mail-wr1-x42e.google.com (mail-wr1-x42e.google.com [IPv6:2a00:1450:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7686653ECC for ; Thu, 23 Feb 2023 11:12:22 -0800 (PST) Received: by mail-wr1-x42e.google.com with SMTP id 6so11156143wrb.11 for ; Thu, 23 Feb 2023 11:12:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=0cOxOkpCD+vr2n7vBER3mbkwWwlvY2KHB3oBnHbXr/U=; b=ErntIUgAGEyRKXt4RMT66Pr0KsOFVw3vBflYFgfNggAyszQJLjPK+0lmvNVh2KXY7g wLgsBRVHOmbmRWbenYGMIxstY0+viUEq09wJYgsdb0oa72GZHZyRNICptybAqmyCeY/4 JSfHCnSohGbanQEtvvBqQOiPK3IGTQsbhuRvCIkXAtcI/l1zNfcYBX53buZ7xaGJm9Si tIx8lFSAKy+fGR9TzyT8jccKHgDF22drQHBcbFUumT4w4Cm+cupSv8AmEqAky0qy3J34 Dsakgq/7oGhgzOOA/T+PDYwDyEqdsiF1RVugLC3zmLNw4vIThARfDuXru7zf/cuVHvwj jtaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=0cOxOkpCD+vr2n7vBER3mbkwWwlvY2KHB3oBnHbXr/U=; b=cnuqjIz3lvD1npjsjRjhubUZ98fhmn9JN/xVFQK/tTmkCIGsrN6sik708l5aS+rU+4 boC7deZTvHwKIFcXpnVZ879wxuBbA8yIev1+wTUt3IPNigsf46v0LEgk4t5ygRHs8TGJ SPlYGL+ZrmKqzRLm3PJAW85xVkTYdEosY2jqTmxgsUPnIruPDdv4QebOrSatDbwAENuM wwAf50qkEJeagt+gQvO75nhJ9DbcMSC7TsDnFmF2DfCSm3pR4jRGRxtpQeV30HOWaJt3 +kjzaN1qLq4diw3QWueP6KmX8zB1qwzc3WcrRdLW8ahN71KLURzt+Pq69EQVraNFXgct NwLQ== X-Gm-Message-State: AO0yUKVPpVUzBIODJ59X3T6LWBCcYTnmgdng6v7/kF7hHhmBHB1EmnR0 GFSHU99rURFzQ0PFOA/ZPqJHTw== X-Google-Smtp-Source: AK7set+dbHx4azJ+uDT3nkXu+TSQadSyr2qdot7zwaRJcS8pl5LZjAZsdxZtDowpkUSbv7n0SuNgfA== X-Received: by 2002:adf:ea11:0:b0:2c7:a39:7453 with SMTP id q17-20020adfea11000000b002c70a397453mr6424268wrm.54.1677179509837; Thu, 23 Feb 2023 11:11:49 -0800 (PST) Received: from usaari01.cust.communityfibre.co.uk ([2a02:6b6a:b566:0:5ee0:5af0:64bd:6198]) by smtp.gmail.com with ESMTPSA id b15-20020a5d4b8f000000b002c561805a4csm12957286wrt.45.2023.02.23.11.11.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Feb 2023 11:11:49 -0800 (PST) From: Usama Arif To: dwmw2@infradead.org, tglx@linutronix.de, kim.phillips@amd.com, brgerst@gmail.com Cc: piotrgorski@cachyos.org, oleksandr@natalenko.name, arjan@linux.intel.com, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, x86@kernel.org, pbonzini@redhat.com, paulmck@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, rcu@vger.kernel.org, mimoja@mimoja.de, hewenliang4@huawei.com, thomas.lendacky@amd.com, seanjc@google.com, pmenzel@molgen.mpg.de, fam.zheng@bytedance.com, punit.agrawal@bytedance.com, simon.evans@bytedance.com, liangma@liangbit.com, David Woodhouse , Usama Arif Subject: [PATCH v11 07/12] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Date: Thu, 23 Feb 2023 19:11:35 +0000 Message-Id: <20230223191140.4155012-8-usama.arif@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230223191140.4155012-1-usama.arif@bytedance.com> References: <20230223191140.4155012-1-usama.arif@bytedance.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Woodhouse When the APs can find their own APIC ID without assistance, perform the AP bringup in parallel. Register a CPUHP_BP_PARALLEL_DYN stage "x86/cpu:kick" which just calls do_boot_cpu() to deliver INIT/SIPI/SIPI to each AP in turn before the normal native_cpu_up() does the rest of the hand-holding. The APs will then take turns through the real mode code (which has its own bitlock for exclusion) until they make it to their own stack, then proceed through the first few lines of start_secondary() and execute these parts in parallel: start_secondary() -> cr4_init() -> (some 32-bit only stuff so not in the parallel cases) -> cpu_init_secondary() -> cpu_init_exception_handling() -> cpu_init() -> wait_for_master_cpu() At this point they wait for the BSP to set their bit in cpu_callout_mask (from do_wait_cpu_initialized()), and release them to continue through the rest of cpu_init() and beyond. This reduces the time taken for bringup on my 28-thread Haswell system from about 120ms to 80ms. On a socket 96-thread Skylake it takes the bringup time from 500ms to 100ms. There is more speedup to be had by doing the remaining parts in parallel too — especially notify_cpu_starting() in which the AP takes itself through all the stages from CPUHP_BRINGUP_CPU to CPUHP_ONLINE. But those require careful auditing to ensure they are reentrant, before we can go that far. Signed-off-by: David Woodhouse Signed-off-by: Usama Arif Tested-by: Paul E. McKenney Tested-by: Kim Phillips Tested-by: Oleksandr Natalenko Tested-by: Michael Kelley --- arch/x86/kernel/smpboot.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 74c76c78f7d2..85ce6a8978ff 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -57,6 +57,7 @@ #include #include #include +#include #include #include @@ -1325,9 +1326,12 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle) { int ret; - ret = do_cpu_up(cpu, tidle); - if (ret) - return ret; + /* If parallel AP bringup isn't enabled, perform the first steps now. */ + if (!do_parallel_bringup) { + ret = do_cpu_up(cpu, tidle); + if (ret) + return ret; + } ret = do_wait_cpu_initialized(cpu); if (ret) @@ -1349,6 +1353,12 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle) return ret; } +/* Bringup step one: Send INIT/SIPI to the target AP */ +static int native_cpu_kick(unsigned int cpu) +{ + return do_cpu_up(cpu, idle_thread_get(cpu)); +} + /** * arch_disable_smp_support() - disables SMP support for x86 at runtime */ @@ -1566,6 +1576,11 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) smpboot_control = STARTUP_SECONDARY | STARTUP_APICID_CPUID_01; } + if (do_parallel_bringup) { + cpuhp_setup_state_nocalls(CPUHP_BP_PARALLEL_DYN, "x86/cpu:kick", + native_cpu_kick, NULL); + } + snp_set_wakeup_secondary_cpu(); }