From nobody Fri Feb 13 01:40:02 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 9804B3838F for ; Mon, 3 Jun 2024 19:38:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717443528; cv=none; b=B+ofimpiZ7E2hx0UtDWHStSRyK9dlNCMJFxvPJygZH599/ZmDpR1gE2pA8EE1iDQ6YMW1CLhiT5SicCSZ0qv64W4SpVMXvWel+yUfw7OFydfwyS6HepFMXkcUg1FV3ppodQkU3Ofj39tTDv8ompDw4z16CB3eUlV8wDTEnXpYtU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717443528; c=relaxed/simple; bh=rBLf380duWASA+BHiufGZGEMzz9Q+lZrGAfvletpReU=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=IOZFLjqypLgNqDHFsdBxDTaTvlZQZ1FVx9TnyIUjoYCPbil9pyDE2+9RbodY9Emsb+FVhwAv0QfyyMzSWzzqpT8p37hg5zte4/4AcMl53GjBwtgtUPeTzsA3czxVehZ0mtzOKu3ZAzaaog55izgUzMXhTOGqTjDyEKRqL7cZDYA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=V4wKsMz1; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="V4wKsMz1" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1717443525; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=ZRP6XsL9a0oYCQIdSQy4MFeP5v2pU/iHsNba/xl+gzk=; b=V4wKsMz1LVCcCtq4Nh4wkjKUWtfnL/0z1nqJD4XWyU1o7Pnifi6/bKfsvI6i7j3s6CVUk2 LBnQhpXW5OrmBgyLQa3VaSd3XdcQNB0HXg4QSid9ui36UXrDJ3hqunhbOosnCPJDYGsOT3 FAOg0j2tLkffj61saG7R0y/lRtSixUE= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-336-e6GYhzR6PTecxpOJjk52Hg-1; Mon, 03 Jun 2024 15:38:42 -0400 X-MC-Unique: e6GYhzR6PTecxpOJjk52Hg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id AE031184882A; Mon, 3 Jun 2024 19:38:41 +0000 (UTC) Received: from llong.com (unknown [10.22.16.27]) by smtp.corp.redhat.com (Postfix) with ESMTP id 92A211C0D105; Mon, 3 Jun 2024 19:38:40 +0000 (UTC) From: Waiman Long To: Tejun Heo , Zefan Li , Johannes Weiner Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Xavier , Waiman Long Subject: [PATCH-cgroup] cgroup/cpuset: Optimize isolated partition only generate_sched_domains() calls Date: Mon, 3 Jun 2024 15:38:22 -0400 Message-Id: <20240603193822.1209999-1-longman@redhat.com> 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-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 Content-Type: text/plain; charset="utf-8" If only isolated partitions are being created underneath the cgroup root, there will only be one sched domain with top_cpuset.effective_cpus. We can skip the unnecessary sched domains scanning code and save some cycles. Signed-off-by: Waiman Long --- kernel/cgroup/cpuset.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 315f8cbd6d35..f9b97f65e204 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -964,6 +964,7 @@ static int generate_sched_domains(cpumask_var_t **domai= ns, =20 /* Special case for the 99% of systems with one, full, sched domain */ if (root_load_balance && !top_cpuset.nr_subparts) { +single_root_domain: ndoms =3D 1; doms =3D alloc_sched_domains(ndoms); if (!doms) @@ -1022,6 +1023,13 @@ static int generate_sched_domains(cpumask_var_t **do= mains, } rcu_read_unlock(); =20 + /* + * If there are only isolated partitions underneath the cgroup root, + * we can optimize out unneeded sched domains scanning. + */ + if (root_load_balance && (csn =3D=3D 1)) + goto single_root_domain; + for (i =3D 0; i < csn; i++) csa[i]->pn =3D i; ndoms =3D csn; --=20 2.39.3