From patchwork Tue Feb 21 22:33:51 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Usama Arif X-Patchwork-Id: 13148478 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 1614CC61DA3 for ; Tue, 21 Feb 2023 22:36:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230218AbjBUWgw (ORCPT ); Tue, 21 Feb 2023 17:36:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58216 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230359AbjBUWgl (ORCPT ); Tue, 21 Feb 2023 17:36:41 -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 22BB432E67 for ; Tue, 21 Feb 2023 14:35:51 -0800 (PST) Received: by mail-wr1-x42e.google.com with SMTP id l1so5725131wry.10 for ; Tue, 21 Feb 2023 14:35:51 -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=NT0Eusw18gI70sCCLpWRO1h/3KoOWH0Kl/jfZNvB0/o=; b=owPCV4w3lTZs8563Ro8jzNqVAHV29fDptPQ9cq7ZQwDUurVoCmzz+Yv57SWEeM/qA5 H7jvrPh2gMiLGxaNzU8g4inNNHpVQRBDJncFtn8BtYQfIVfPwnpRYCFBgYrGk5EEZlKh IEYfQXy2WpBc375AEN7UxIWlcFvxtn5qsefgQyEHPQQlNbOvFtn8VDVqWBRLoYBFsIsN phmM7LHYam2Ms9u4Kg5hNdqjcW93lJ3bXkgl08/c/5+6plIvMKXP5Tiy4iXksVia6vva fPOdTTd382aSKKePa/BhbskkSDRe3JkjD/5YujhUrWIg8A+Qksyg7/7jDuaiExQcppbP vwng== 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=NT0Eusw18gI70sCCLpWRO1h/3KoOWH0Kl/jfZNvB0/o=; b=oiV3g2gIrvV0FeI/JC2fAzJ8Ib4l1iQvuQKRvQlufmVdSE6fs4VDfH1uGf/5L6Jw0F FZl2hSiXJaj7HDSFtUeK0D6kRaPjOOs0ZXK27CdDvXgxjWtWMgOkEa7OUYFyUguo59Pu Nqf4ZeJzRPQ5GbCisl7LvUb09vwiNnWWzFx0davk2Pl73GG27G50K1Mt9OF9CITlwLyc vhTayhzjdlemdCzPZwUrYvu2M78pqiqQeeEQL7eEpvTVjeStfp2WZAl2cNqxoNtV82qW tStV41/joJ3hNt+B4dbfW50gj7BqFesZpVV52wWWDAGTijMQ9Z/t5drTHS5B3hjVga9E yMqQ== X-Gm-Message-State: AO0yUKVakhcIwCIW4D7e+FXKfpyBcxmGGwlSxevaOuxA835RaIyR8xxh st42PLstBueuL5hrTWPDO7KVNg== X-Google-Smtp-Source: AK7set+QYZOoObU5r9Lv1ztUjqQnBL32311UcNp7RFdUUeqIUqp51mQ4bB4EECCUqF0zBzlSzRoWLQ== X-Received: by 2002:a05:6000:11cd:b0:2c5:594b:10d1 with SMTP id i13-20020a05600011cd00b002c5594b10d1mr6269275wrx.23.1677018949655; Tue, 21 Feb 2023 14:35:49 -0800 (PST) Received: from usaari01.cust.communityfibre.co.uk ([2a02:6b6a:b566:0:1a14:8be6:b3a9:a95e]) by smtp.gmail.com with ESMTPSA id u13-20020a5d434d000000b002c55ec7f661sm4501254wrr.5.2023.02.21.14.35.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Feb 2023 14:35:49 -0800 (PST) From: Usama Arif To: dwmw2@infradead.org, tglx@linutronix.de, kim.phillips@amd.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 v10 7/8] x86/smpboot: Send INIT/SIPI/SIPI to secondary CPUs in parallel Date: Tue, 21 Feb 2023 22:33:51 +0000 Message-Id: <20230221223352.2288528-8-usama.arif@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230221223352.2288528-1-usama.arif@bytedance.com> References: <20230221223352.2288528-1-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 6924d91b69ca..a8f52e03d55d 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(); }