From patchwork Sun Feb 26 11:08:01 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Usama Arif X-Patchwork-Id: 13152364 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 EF999C6FA8E for ; Sun, 26 Feb 2023 11:09:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229805AbjBZLJ0 (ORCPT ); Sun, 26 Feb 2023 06:09:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229776AbjBZLJE (ORCPT ); Sun, 26 Feb 2023 06:09:04 -0500 Received: from mail-wm1-x334.google.com (mail-wm1-x334.google.com [IPv6:2a00:1450:4864:20::334]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1E7DBEC4D for ; Sun, 26 Feb 2023 03:08:15 -0800 (PST) Received: by mail-wm1-x334.google.com with SMTP id t25-20020a1c7719000000b003eb052cc5ccso4824918wmi.4 for ; Sun, 26 Feb 2023 03:08:15 -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=Rv4YBkExnEbzjmvRGSVdLlKzdSs1hoLH3+gZkX3hIJM=; b=DJ0qn754KoOY7lszedXqM0cvktd4MIlEDstLHXsvijRzw7VZtckVr4f+/5tRRSmKHU gdDRywi3/sCcc7cHk3Z1pMDmtOJBx42sx44E2WV0E5kwwaYFh0qPiytCfjob5b6Whm6M JoD/FuFOZZRjwBfN/BXF6UWeFn4h1MBx/LQRtZGy6q9qXLvTqOP1wlhSDMW34m8nEXIL 5j4L2Hm+EO5Z2aUvxXx4NkNje0MQfjveISORHATz2z5n4bl/Cjjio/sv53EwV2Lz9yR4 ZLxVoK7Ra+QQNJID4t6OiAb0CvXGuzbUjPqd8warO8sN+vc5QX5e09GyuhHyU4um/Lo4 3BHA== 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=Rv4YBkExnEbzjmvRGSVdLlKzdSs1hoLH3+gZkX3hIJM=; b=uhWZAUeMq0+FuLevtYYVONcFXmFsDnMagn5ZmDVDmJOTwDzFV0G3eXRVIDgLFfijgw P3D3MBhgDd1HnOTNmq7a+IlTMjhPzDN7L7miFvvHs4c/HRZzgghMpBHk/U42qIVPZjaX hD0/AzDsKtuba4IsL9nUv31LCCaJlxv91TbsuVwBO1ZrG5emnlUW8Noo2xmU3d6HvS79 3YtC2o9HrD+IKhBpUpi5F1LGJZ2kF4Dz5hTu2nVrsC4fiKOObO5etETlX0W/JKaIJdEy Uv5YK0aXZpmaaum83W3ALTO/NRqRx5bQAZQIJGRV1RDCr1MUkLKKkWoKKkjnLtMTZj92 IKIg== X-Gm-Message-State: AO0yUKUzOVnf5YJ/hWI6plbaddGf4OaAG9TABAGDQcSKlGzo5rpoit28 LLfIyAGu4cd9yn1e7OmOj2Wk9w== X-Google-Smtp-Source: AK7set8mHGT2VnCThEqOMgIy/Fuquza1CoWNEJQk3uaHqxCiEMo9Z60UV7yiXPOSZC5v+cIlL4JZnw== X-Received: by 2002:a05:600c:4da3:b0:3eb:2da4:f304 with SMTP id v35-20020a05600c4da300b003eb2da4f304mr5025546wmp.17.1677409693572; Sun, 26 Feb 2023 03:08:13 -0800 (PST) Received: from usaari01.cust.communityfibre.co.uk ([2a02:6b6a:b566:0:df7b:4668:3e23:d0c9]) by smtp.gmail.com with ESMTPSA id v22-20020a1cf716000000b003e1fee8baacsm9157318wmh.25.2023.02.26.03.08.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 26 Feb 2023 03:08:13 -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 v12 10/11] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Date: Sun, 26 Feb 2023 11:08:01 +0000 Message-Id: <20230226110802.103134-11-usama.arif@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230226110802.103134-1-usama.arif@bytedance.com> References: <20230226110802.103134-1-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 --- 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 19b9b89b7458..711573cd9b87 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_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(); }