From nobody Thu Feb 12 08:01:39 2026 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 45807EED61A for ; Fri, 15 Sep 2023 18:51:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236609AbjIOSvO (ORCPT ); Fri, 15 Sep 2023 14:51:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236997AbjIOSvF (ORCPT ); Fri, 15 Sep 2023 14:51:05 -0400 Received: from mail-pj1-x1033.google.com (mail-pj1-x1033.google.com [IPv6:2607:f8b0:4864:20::1033]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4AFF446BC for ; Fri, 15 Sep 2023 11:49:42 -0700 (PDT) Received: by mail-pj1-x1033.google.com with SMTP id 98e67ed59e1d1-274928c74b0so1015660a91.3 for ; Fri, 15 Sep 2023 11:49:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20230601.gappssmtp.com; s=20230601; t=1694803780; x=1695408580; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=uYSmTOF4KYS04RS6/kkM9Rhx+w8lvbwAPz9Fg6XUkeE=; b=DJmguOdiOtprnjBvUxG82Na5H7guQg6deMgaKMaDMLDHuYPUryvAuJYU3HH2ZKuZ05 XWDEeFG/yDhOKlODgCMDcC6JWGrXrVbWZLHrO/SRfrbsMmxUlBwBmnhX7kbG135QyrfD ZLJHzfYdXz5wM0UMQK95zP3A86EwXdgU6miTDEHixq9+CJAcZHzRLhEe/X7N/veOZm30 tWM2c/Cc++Ww0fDortZJptpZz+9bqgWvVyxMBYcjbxZde3ULyTQJUzbS3IWUO7FdyHds nEQr9Mt5rbhOcUs1/h7wpkSXWDnLlpyrOuVM2FaGlaY59TKnp1Vz4IDpk0iWYgTGttda b9oA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1694803780; x=1695408580; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=uYSmTOF4KYS04RS6/kkM9Rhx+w8lvbwAPz9Fg6XUkeE=; b=WEr/Ox2Y2vJMmSZiPfpniY16GveizVUVrzCCqSGgXaM2eeiOc+WyzMvy93D/ftM8RY hFQALPh+hCcRtFCzHnIVHbL9Tlu0Ig/WcK4UeQhEm9cFfMHE6GfBbS4jIRXz4VFiwOO/ hERMUbnY+7j1jaHCALsvZTY0453enNoLc4UZb8hoAn3VniEOkRKsaTOF0Byy7cgYKSSL Zyb8ZSeb8zYDvBJR5jxnFLKH7w4z2YakDPoOgrqrYrJBCLlQfOfP0o7eIH+tU6KSInT8 j/k8y8+QtTW3GvzWJlB8LtoGFy6FJl/JG9d5DXm8zAmuqP+lkFI12QPYWxPYJ6XRSI72 WXuw== X-Gm-Message-State: AOJu0YwsIKWMjWAVAEkcrRJP0HkpSLoPcAU+Ree6B/V0Vy5bQorBGH+G CwW/TET8VNt9clB1PlMm+1f2ew== X-Google-Smtp-Source: AGHT+IGL1HqMkQEx+0inVSPfre6GGNigTDq3ef/4CTrXmyvJ3uVn8SIT88LCmaonmmg+jb/AZHsXww== X-Received: by 2002:a17:90a:c913:b0:268:1d1e:baaf with SMTP id v19-20020a17090ac91300b002681d1ebaafmr2542117pjt.17.1694803780056; Fri, 15 Sep 2023 11:49:40 -0700 (PDT) Received: from evan.ba.rivosinc.com ([66.220.2.162]) by smtp.gmail.com with ESMTPSA id o6-20020a17090ad24600b00268188ea4b9sm3397849pjw.19.2023.09.15.11.49.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Sep 2023 11:49:39 -0700 (PDT) From: Evan Green To: Palmer Dabbelt Cc: David Laight , Jisheng Zhang , Evan Green , Albert Ou , Andrew Jones , Anup Patel , Conor Dooley , Greentime Hu , Heiko Stuebner , Ley Foon Tan , Marc Zyngier , Palmer Dabbelt , Paul Walmsley , Sunil V L , linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: [PATCH] RISC-V: Probe misaligned access speed in parallel Date: Fri, 15 Sep 2023 11:49:03 -0700 Message-Id: <20230915184904.1976183-1-evan@rivosinc.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Probing for misaligned access speed takes about 0.06 seconds. On a system with 64 cores, doing this in smp_callin() means it's done serially, extending boot time by 3.8 seconds. That's a lot of boot time. Instead of measuring each CPU serially, let's do the measurements on all CPUs in parallel. If we disable preemption on all CPUs, the jiffies stop ticking, so we can do this in stages of 1) everybody except core 0, then 2) core 0. The measurement call in smp_callin() stays around, but is now conditionalized to only run if a new CPU shows up after the round of in-parallel measurements has run. The goal is to have the measurement call not run during boot or suspend/resume, but only on a hotplug addition. Signed-off-by: Evan Green Reported-by: Jisheng Zhang Reviewed-by: Andrew Jones --- Jisheng, I didn't add your Tested-by tag since the patch evolved from the one you tested. Hopefully this one brings you the same result. --- arch/riscv/include/asm/cpufeature.h | 3 ++- arch/riscv/kernel/cpufeature.c | 28 +++++++++++++++++++++++----- arch/riscv/kernel/smpboot.c | 11 ++++++++++- 3 files changed, 35 insertions(+), 7 deletions(-) diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/c= pufeature.h index d0345bd659c9..19e7817eba10 100644 --- a/arch/riscv/include/asm/cpufeature.h +++ b/arch/riscv/include/asm/cpufeature.h @@ -30,6 +30,7 @@ DECLARE_PER_CPU(long, misaligned_access_speed); /* Per-cpu ISA extensions. */ extern struct riscv_isainfo hart_isa[NR_CPUS]; =20 -void check_unaligned_access(int cpu); +extern bool misaligned_speed_measured; +int check_unaligned_access(void *unused); =20 #endif diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 1cfbba65d11a..8eb36e1dfb95 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -42,6 +42,9 @@ struct riscv_isainfo hart_isa[NR_CPUS]; /* Performance information */ DEFINE_PER_CPU(long, misaligned_access_speed); =20 +/* Boot-time in-parallel unaligned access measurement has occurred. */ +bool misaligned_speed_measured; + /** * riscv_isa_extension_base() - Get base extension word * @@ -556,8 +559,9 @@ unsigned long riscv_get_elf_hwcap(void) return hwcap; } =20 -void check_unaligned_access(int cpu) +int check_unaligned_access(void *unused) { + int cpu =3D smp_processor_id(); u64 start_cycles, end_cycles; u64 word_cycles; u64 byte_cycles; @@ -571,7 +575,7 @@ void check_unaligned_access(int cpu) page =3D alloc_pages(GFP_NOWAIT, get_order(MISALIGNED_BUFFER_SIZE)); if (!page) { pr_warn("Can't alloc pages to measure memcpy performance"); - return; + return 0; } =20 /* Make an unaligned destination buffer. */ @@ -643,15 +647,29 @@ void check_unaligned_access(int cpu) =20 out: __free_pages(page, get_order(MISALIGNED_BUFFER_SIZE)); + return 0; +} + +static void check_unaligned_access_nonboot_cpu(void *param) +{ + if (smp_processor_id() !=3D 0) + check_unaligned_access(param); } =20 -static int check_unaligned_access_boot_cpu(void) +static int check_unaligned_access_all_cpus(void) { - check_unaligned_access(0); + /* Check everybody except 0, who stays behind to tend jiffies. */ + on_each_cpu(check_unaligned_access_nonboot_cpu, NULL, 1); + + /* Check core 0. */ + smp_call_on_cpu(0, check_unaligned_access, NULL, true); + + /* Boot-time measurements are complete. */ + misaligned_speed_measured =3D true; return 0; } =20 -arch_initcall(check_unaligned_access_boot_cpu); +arch_initcall(check_unaligned_access_all_cpus); =20 #ifdef CONFIG_RISCV_ALTERNATIVE /* diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c index 1b8da4e40a4d..39322ae20a75 100644 --- a/arch/riscv/kernel/smpboot.c +++ b/arch/riscv/kernel/smpboot.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include @@ -246,7 +247,15 @@ asmlinkage __visible void smp_callin(void) =20 numa_add_cpu(curr_cpuid); set_cpu_online(curr_cpuid, 1); - check_unaligned_access(curr_cpuid); + + /* + * Boot-time misaligned access speed measurements are done in parallel + * in an initcall. Only measure here for hotplug. + */ + if (misaligned_speed_measured && + (per_cpu(misaligned_access_speed, curr_cpuid) =3D=3D RISCV_HWPROBE_MI= SALIGNED_UNKNOWN)) { + check_unaligned_access(NULL); + } =20 if (has_vector()) { if (riscv_v_setup_vsize()) --=20 2.34.1