From nobody Wed Oct 8 21:39:07 2025 Received: from sender4-op-o15.zoho.com (sender4-op-o15.zoho.com [136.143.188.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5ABD522A4EF for ; Tue, 24 Jun 2025 08:57:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.15 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750755432; cv=pass; b=T6N+MabVr6WrsalkxNaNpKzYbMUO0nKoVv1V6ya2tk0ogGmgBN7ap11sh9H+aDGCNEPZX7b1CR1cenVphMtjnSz54/q8eN7n9iFEbS52bpB/xeYcdSNYA0DTrPnbC8CjCe2228M/pY5ry7fZ4MgPOtUOc3TDU6QX0YjU55u963U= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750755432; c=relaxed/simple; bh=nmVLwi1/CTdz2eqx2WEHJ7bQ8fUtwfjpmfF6T8BrT6E=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PqUgPwBh7IXWXVLNq7jtCHzfs7O7YpeDaSEZmMulGAWc39d/gXE6BJznowquBZo5vv3yznmEmPTsri7e15KjC9t9cCN4mezwEzS795GODtZmGnDKLI7CVvDn1KHZrbJ6NchafYJA/yphwcPtNn6SKcRDb1RRbXbAHy+gtM5sZxY= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux.beauty; spf=pass smtp.mailfrom=linux.beauty; dkim=pass (1024-bit key) header.d=linux.beauty header.i=me@linux.beauty header.b=I7gK4ZWz; arc=pass smtp.client-ip=136.143.188.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux.beauty Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.beauty Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.beauty header.i=me@linux.beauty header.b="I7gK4ZWz" ARC-Seal: i=1; a=rsa-sha256; t=1750755371; cv=none; d=zohomail.com; s=zohoarc; b=ZtzmRAQKk1FqUr8qsAQUjfP51txqx4x4H4FXWZppKzij5pDQ5JeztZ+AeCDvON0zFBMm7xik4HLZA+18OsYsdrCt4/E49N+SEBvD5jt5iVKt26encunqqFf4ff24aprZBGP1K7TdZleFxaia4k0xLvIzSz1tfDCAix4Zw5GPRmU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1750755371; h=Content-Transfer-Encoding:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To:Cc; bh=bc85tfo2Sm8Fs+oMeJAqWaHkWG07JkXoL87FcsQ3zbg=; b=hBGZFa2dZwdudXGkNfQbVYUN0H2WOHO0A/VgCUKJNbN6STwBXid5KYKcZYMXfZ8tmfgRUICzOBMkxi75BCd8uyoyREtMy30cWOUamgzTaY4nSNEZaApH5sJ3ZCpUnA7RKOVwzWxjHOtmBZEv7NA4iT34j3YmRL50Sd8Gxw4kktM= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=linux.beauty; spf=pass smtp.mailfrom=me@linux.beauty; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1750755371; s=zmail; d=linux.beauty; i=me@linux.beauty; h=From:From:To:To:Subject:Subject:Date:Date:Message-ID:In-Reply-To:References:MIME-Version:Content-Transfer-Encoding:Message-Id:Reply-To:Cc; bh=bc85tfo2Sm8Fs+oMeJAqWaHkWG07JkXoL87FcsQ3zbg=; b=I7gK4ZWzClbL7Jqpag+MR/NOty1807qpaL8lmsW1xPc4WG7bJEFnvIT+L6ZGqKnm xE1eOhLgtUt2R8lmSvhMmIbiBQkjbu0Vc4zWhpAs2xkF/Lr3eQZ4O7elljhJRHR57c3 /0izoHoFBI5LbkkPSg3+UHaaCW+9n5aYrA0N1Zy8= Received: by mx.zohomail.com with SMTPS id 175075536939152.530146864584935; Tue, 24 Jun 2025 01:56:09 -0700 (PDT) From: Li Chen To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , "Rafael J . Wysocki" , Peter Zijlstra , K Prateek Nayak , Sohil Mehta , Brian Gerst , Patryk Wlazlyn , linux-kernel@vger.kernel.org, Li Chen Subject: [PATCH V2 1/2] x86/smpboot: Decrapify build_sched_topology() Date: Tue, 24 Jun 2025 16:55:56 +0800 Message-ID: <20250624085559.69436-2-me@linux.beauty> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250624085559.69436-1-me@linux.beauty> References: <20250624085559.69436-1-me@linux.beauty> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMailClient: External Content-Type: text/plain; charset="utf-8" From: Thomas Gleixner The #ifdeffery and the initializers in build_sched_topology() are just disgusting. The SCHED_SMT #ifdef is also pointless because SCHED_SMT is unconditionally enabled when SMP is enabled. Statically initialize the domain levels in the topology array and let build_sched_topology() invalidate the package domain level when NUMA in package is available. Signed-off-by: Thomas Gleixner --- changelog: v2: fix wording issue as suggested by Thomas [1] [1]: https://www.spinics.net/lists/kernel/msg5732082.html arch/x86/kernel/smpboot.c | 45 +++++++++++++++------------------------ 1 file changed, 17 insertions(+), 28 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index fc78c2325fd29..7d202f9785362 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -478,43 +478,32 @@ static int x86_cluster_flags(void) */ static bool x86_has_numa_in_package; =20 -static struct sched_domain_topology_level x86_topology[6]; +#define DOMAIN(maskfn, flagsfn, dname) { .mask =3D maskfn, .sd_flags =3D f= lagsfn, .name =3D #dname } =20 -static void __init build_sched_topology(void) -{ - int i =3D 0; - -#ifdef CONFIG_SCHED_SMT - x86_topology[i++] =3D (struct sched_domain_topology_level){ - cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) - }; -#endif +static struct sched_domain_topology_level x86_topology[] =3D { + DOMAIN(cpu_smt_mask, cpu_smt_flags, SMT), #ifdef CONFIG_SCHED_CLUSTER - x86_topology[i++] =3D (struct sched_domain_topology_level){ - cpu_clustergroup_mask, x86_cluster_flags, SD_INIT_NAME(CLS) - }; + DOMAIN(cpu_clustergroup_mask, x86_cluster_flags, CLS), #endif #ifdef CONFIG_SCHED_MC - x86_topology[i++] =3D (struct sched_domain_topology_level){ - cpu_coregroup_mask, x86_core_flags, SD_INIT_NAME(MC) - }; + DOMAIN(cpu_coregroup_mask, x86_core_flags, MC), #endif - /* - * When there is NUMA topology inside the package skip the PKG domain - * since the NUMA domains will auto-magically create the right spanning - * domains based on the SLIT. - */ - if (!x86_has_numa_in_package) { - x86_topology[i++] =3D (struct sched_domain_topology_level){ - cpu_cpu_mask, x86_sched_itmt_flags, SD_INIT_NAME(PKG) - }; - } + DOMAIN(cpu_cpu_mask, x86_sched_itmt_flags, PKG), + { NULL }, +}; =20 +static void __init build_sched_topology(void) +{ /* - * There must be one trailing NULL entry left. + * When there is NUMA topology inside the package invalidate the + * PKG domain since the NUMA domains will auto-magically create the + * right spanning domains based on the SLIT. */ - BUG_ON(i >=3D ARRAY_SIZE(x86_topology)-1); + if (x86_has_numa_in_package) { + unsigned int pkgdom =3D ARRAY_SIZE(x86_topology) - 2; =20 + memset(&x86_topology[pkgdom], 0, sizeof(x86_topology[pkgdom])); + } set_sched_topology(x86_topology); } =20 --=20 2.49.0 From nobody Wed Oct 8 21:39:07 2025 Received: from sender4-op-o15.zoho.com (sender4-op-o15.zoho.com [136.143.188.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E2B7426B740 for ; Tue, 24 Jun 2025 08:57:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.15 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750755467; cv=pass; b=pORu10HDL8/3e/473PIvnw+OxeMjinYRBSMSoGJTkEimh+JEaCek80gCQBPI4tAXHsKFC5VU4mvlucteqzWlTc0SRwlYZga3jnuVgq5QovSwmfhBK6e8q3tOyBCBKhUa4FKBHf2671wwT00Rx+CCFfI3btpB9BFA+UU+8Vc1B30= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750755467; c=relaxed/simple; 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bh=0dsn2ucVT8C5oLjA0ZF1ibISznlHMPT5N6s+8AW9Sz4=; b=MF9B5pR5YkOVeSxrjD6+vW7fQJa8RQEPJ7kHblPbJCNS0Sph4P8bNVE4DRxk+NWA 2f+5oXT1MfuLTBeBbb8gT3MmHe7YTB3fGOyRGa4Au32Bmdw/x727FVQxl5nZEfStJfT YOnfKuN/8WckiNJ6fCIGcXsJGnVYNO5O1DBc3ISQ= Received: by mx.zohomail.com with SMTPS id 1750755374157259.65646699168974; Tue, 24 Jun 2025 01:56:14 -0700 (PDT) From: Li Chen To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , "Rafael J . Wysocki" , Peter Zijlstra , K Prateek Nayak , Sohil Mehta , Brian Gerst , Patryk Wlazlyn , linux-kernel@vger.kernel.org, Li Chen Subject: [PATCH V2 2/2] x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled Date: Tue, 24 Jun 2025 16:55:57 +0800 Message-ID: <20250624085559.69436-3-me@linux.beauty> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250624085559.69436-1-me@linux.beauty> References: <20250624085559.69436-1-me@linux.beauty> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-ZohoMailClient: External From: Li Chen Currently, the SMT domain is added into sched_domain_topology by default if CONFIG_SCHED_SMT is enabled. If cpu_attach_domain finds that the CPU SMT domain=E2=80=99s cpumask_weight is just 1, it will destroy it. On a large machine, such as one with 512 cores, this results in 512 redundant domain attach/destroy operations. Avoid these unnecessary operations by simply checking cpu_smt_num_threads and not inserting SMT domain into x86_topology if the SMT domain is not enabled. Signed-off-by: Li Chen --- arch/x86/kernel/smpboot.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 7d202f9785362..9ff8b10715cc1 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -492,8 +492,24 @@ static struct sched_domain_topology_level x86_topology= [] =3D { { NULL }, }; =20 +static void __init maybe_remove_smt_level(void) +{ + if (cpu_smt_num_threads <=3D 1) { + /* + * SMT level is x86_topology[0]. Shift the array left by one, + * keep the sentinel { NULL } at the end. + */ + memmove(&x86_topology[0], &x86_topology[1], + sizeof(x86_topology) - sizeof(x86_topology[0])); + memset(&x86_topology[ARRAY_SIZE(x86_topology) - 1], 0, + sizeof(x86_topology[0])); + } +} + static void __init build_sched_topology(void) { + maybe_remove_smt_level(); + /* * When there is NUMA topology inside the package invalidate the * PKG domain since the NUMA domains will auto-magically create the --=20 2.49.0