From patchwork Wed Feb 15 14:54:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Usama Arif X-Patchwork-Id: 13141765 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 602E2C636D7 for ; Wed, 15 Feb 2023 14:55:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230040AbjBOOzU (ORCPT ); Wed, 15 Feb 2023 09:55:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50974 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229963AbjBOOzH (ORCPT ); Wed, 15 Feb 2023 09:55:07 -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 C688939BBE for ; Wed, 15 Feb 2023 06:54:36 -0800 (PST) Received: by mail-wr1-x42e.google.com with SMTP id by3so18116395wrb.10 for ; Wed, 15 Feb 2023 06:54:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; 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=JJkpGg1hd8P6OX4RPHIkrzOMjPz7lmvjqBeU21FPpuA=; b=tcdHg6gL/+kmrDf6TMBwvnFfIcz101nGGz3Inam8TJELR9NPia/44bKe58cCe0wion KHhYTtM5JQHVGWkPIJQvS0Pg801b07Sz0tqEwOWT7VkqDg7FrNYl1ho3vnyTmQJyfBwd AKNb4Qbx/3QPWVMJ+ealo/onIWpVGrNLelRhBmyq9YVt99ApYhJ+jmpXsMkCMwQCvTUR XcHyB3YqBuIx5oALw8ygnOcM4MeZHUhQmNkAysqnAOo8sCMHwQeVvHZR0R+bpWuLe5sq Cr7eqqqA6NjXSDEX5DbcmXdJ5jFBjeC7+t5h+aIFic37yrx73YXF1y5DxCQ8rVp7qUF7 4Pcw== 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=JJkpGg1hd8P6OX4RPHIkrzOMjPz7lmvjqBeU21FPpuA=; b=Ru9zB6sIaEseUnmRavDMfT8g3KKj+GTqkDGrvWEwwwmf2NW6zOkERzPapXyAUphVr9 8ry+1YRNK9T7MsgRUViSTmi22OLnJX+n2ClsgLGv8r9K8PWu4vvNUjAtGeQ0ZmbSOjA6 aJQqzUWSGMyZDoztvj3daPBSwO75qGoLjhANJbHvYsAlg69aJNHPqeIxG1DaDBMJgUSr rZT3KcyGBqPFWkE+3AsH5jxNwekU/iyBUgLV1HmUdzPt44PhBynOHUnaptyTVnPk6JVH eZJrty6voIjaVsmWxfZicJN5AJszUM4wDUxmH2UFNJJC+CgMrTBrQfuilQt/8yTKXLj/ nE8w== X-Gm-Message-State: AO0yUKVdPzd+FsDDepEDzGUSn9vW7Ok9HkcYgixKfhCdMMZJe42Thfda 4PfJchWBsVQ3VqVSjCogJ7Bkkg== X-Google-Smtp-Source: AK7set/T0pWPr2ac0iFIDBkuMj5fFQH6npYOyPRhDiy7cZKHer4TH0/f/yhlUIQu8bqE+A2MmHWpbg== X-Received: by 2002:a5d:68c1:0:b0:2c5:58f5:3c40 with SMTP id p1-20020a5d68c1000000b002c558f53c40mr1698253wrw.47.1676472875295; Wed, 15 Feb 2023 06:54:35 -0800 (PST) Received: from usaari01.cust.communityfibre.co.uk ([2a02:6b6a:b566:0:8487:6a9a:3a67:11aa]) by smtp.gmail.com with ESMTPSA id t13-20020adfe44d000000b002c557f82e27sm8495508wrm.99.2023.02.15.06.54.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Feb 2023 06:54:34 -0800 (PST) From: Usama Arif To: dwmw2@infradead.org, tglx@linutronix.de, kim.phillips@amd.com Cc: 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 v9 7/8] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Date: Wed, 15 Feb 2023 14:54:24 +0000 Message-Id: <20230215145425.420125-8-usama.arif@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230215145425.420125-1-usama.arif@bytedance.com> References: <20230215145425.420125-1-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. [Usama Arif: fixed rebase conflict] Signed-off-by: David Woodhouse Signed-off-by: Usama Arif --- 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 49d6563e4c23..4cea3a0ff503 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(); }