From nobody Wed Oct 8 20:58:43 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 2D1D733E4 for ; Wed, 25 Jun 2025 03:47:38 +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=1750823262; cv=pass; b=U280hu1NByX/qkVFh4Sxm2Dy71Tm0a9ZMSM1qB+Hfw8xBP6LQbYn4pZrisFSVPLuWzReX9YHxAD+Ip5V5bEEP9JpphUN5/SZGlzp9qqrQ08UjBlblbyYyP71oEkOO+1tsynUVVK1vjdOSTWsfzR/6PAWL9pRq7sRyv3gj7je1v0= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750823262; c=relaxed/simple; bh=JP26mKnlstWQd02lHyws56EmzQCjDY8MetuTGwA3c/M=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=MvhsB8Jtu4Hq4X3XKX0cT5MnsLAW9W9dkgr0fT5KPrcYnYkefabmLUI6t1lCA2GtojHRxawrM4AzH9hMZRfAD9CmiYbhwB8wVoWbTsTeHiP7FnQ+/XvKcy6dQ/PPNEfmHWGRgugN7fNlFOtnDzBzwEMOIxOBHD/fTu2C/fjhw5o= 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=asvfwpn8; 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="asvfwpn8" ARC-Seal: i=1; a=rsa-sha256; t=1750823170; cv=none; d=zohomail.com; s=zohoarc; b=H6wU9jp5UENsHWc5Zw+/FuQQker8QugDtICeQqdw/2FiPOGcG9p61gGah4q4704C62wmcsOjId5kIJLS6vuB6gP6P+7tKtbbp9CJIMQW1YbiR75BTtfDkqezBtWf3QEs5od79uBgJ8ezu2wlYEiojEZ9b89s3KRPa6aS8KrW03Q= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1750823170; h=Content-Type: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=RdGgv5ETNd0Zsp1nHqiyPSrLOVxivkC0P66w4cAdGsU=; b=OkCElp4h0yM6T4Hzw0rE0df6JX5z/Rxsf4pnKGNfcYK0XU33wuR1K3yZ9XWtpr7fJgR2Htajv7yE8j7SjX0sZG3rdqD6w+qHifsoGRuuBPHkaOvLnsa0qo74cauO7SM6A2zR4277gE/dghTNE5n6AQXnYMfpAgS1fqgdWpxj9CY= 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=1750823170; 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-Type:Content-Transfer-Encoding:Message-Id:Reply-To:Cc; bh=RdGgv5ETNd0Zsp1nHqiyPSrLOVxivkC0P66w4cAdGsU=; b=asvfwpn8pbFkG2lF6J5zRtDPlVQNn+8B5WOM/67WgCQnPdVrXUvTTp2RVzEYva4E RYDQx4grcyu/s2wf/Na1xWSfVKsnxJorG9NOjA8VNCZss/eSiSWh+8XQyUnNejuUcjZ OYCVw0T5ssoKEen/dO7f9j0vbdX+bVkquhy0yTyE= Received: by mx.zohomail.com with SMTPS id 175082316749596.95391557947278; Tue, 24 Jun 2025 20:46:07 -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, "Gautham R. Shenoy" , Li Chen Subject: [PATCH v3 2/2] x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled Date: Wed, 25 Jun 2025 11:45:50 +0800 Message-ID: <20250625034552.42365-3-me@linux.beauty> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250625034552.42365-1-me@linux.beauty> References: <20250625034552.42365-1-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 cpu_attach_domain() finds that the CPU SMT domain=E2=80=99s cpumask_weig= ht 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 remove SMT domain if the SMT domain is not enabled, and adjust the PKG index accordingly if NUMA-in-package invalidates that level as well. Signed-off-by: Li Chen --- changelog: v2: fix wording issue as suggested by Thomas [1] v3: remove pointless memset and adjust PKG index accordingly, as suggested by Thomas [2]=20 [1]: https://lore.kernel.org/all/87msa2r018.ffs@tglx/ [2]: https://lore.kernel.org/all/875xglntx1.ffs@tglx/ arch/x86/kernel/smpboot.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 7d202f9785362..4b6daa1545445 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -494,13 +494,29 @@ static struct sched_domain_topology_level x86_topolog= y[] =3D { =20 static void __init build_sched_topology(void) { + bool smt_dropped =3D false; + + if (cpu_smt_num_threads <=3D 1) { + /* + * SMT level is x86_topology[0]. Shift the array left by one, + */ + memmove(&x86_topology[0], &x86_topology[1], + sizeof(x86_topology) - sizeof(x86_topology[0])); + smt_dropped =3D true; + } + /* * 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. */ if (x86_has_numa_in_package) { - unsigned int pkgdom =3D ARRAY_SIZE(x86_topology) - 2; + unsigned int pkgdom; + + if (smt_dropped) + pkgdom =3D ARRAY_SIZE(x86_topology) - 3; + else + pkgdom =3D ARRAY_SIZE(x86_topology) - 2; =20 memset(&x86_topology[pkgdom], 0, sizeof(x86_topology[pkgdom])); } --=20 2.49.0