From nobody Mon Dec 1 21:30:03 2025 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (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 DB23C2206AC for ; Mon, 1 Dec 2025 18:32:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.156.1 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764613958; cv=none; b=iC3Tv7wDPHrc09HqetyujYuCXMpg7zqmZyHch5Lqspu3MFw6ScRdtSmAMRUqtE0RkthANsns1a+UKkMg3ohKCrngslD0o7KZBelg500MiR7Ah5gdoxB5lhuBrV3WnZf5Qpqd4DtFxgb03HD6CN5FSdiU5KUIrWqPEoTbCtx/pqI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764613958; c=relaxed/simple; bh=DEZvwjAZ+zpGv0kF1fL/peNfRZQ1HQAXsewsHos63WU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NVuT7nR4WrVSc9BD6xanS1h0YjTQgCJc4kuVWZ/DKtOPbiTjDgtMRgF9jY0R4Qwa5w3ZG1KQgo1L7HUU9v8BoYmAlAcrUeszG+LM2ZUdx4Uy2vy5HtcsrhVse2syaAzPdpjwO0or5aRIkW8lk89ESnUqx7VMCbAZ68MIhqQhEP0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=FkPWWiI3; arc=none smtp.client-ip=148.163.156.1 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="FkPWWiI3" Received: from pps.filterd (m0356517.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 5B1BSJwL000885; Mon, 1 Dec 2025 18:32:10 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:date:from:in-reply-to:message-id :mime-version:references:subject:to; s=pp1; bh=3AziXFYeeXrphX8x4 yU45+pV+B8PoMtr1aVfZ0JST1I=; b=FkPWWiI3tz4xK+ifrOg7Ec6Tsr8W6YjL4 sUKTN672YnBJjui6diIITd/b6nKrXVkewKTvOSOurfe9rFFC7/w/qc5nVFyr2x5d fg7y1WrMpUI3I5TChETRMf6TYVtA8Xv/sZrWbd3Lv46DKfgCQ4LcYfeuLMf5Q+Dy 68luLrtPwsjKvSBHSjZP8tYnNyo9Z2iz4IMpx6fmMecN+vvfZl8c8y9NqjNs+pyC d1j4atpKx1WByW0mM3otFHL+rWJZ0Kkgq7uXRkEBxtYPVLae4ND+h/K9zcY7ZjVw nrzwMj+Y0eF5YgZyHx3MDLnSlLN0NqBwarxazYSCjq6jTaDWXYZAQ== Received: from ppma11.dal12v.mail.ibm.com (db.9e.1632.ip4.static.sl-reverse.com [50.22.158.219]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4aqrj9gve5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 01 Dec 2025 18:32:10 +0000 (GMT) Received: from pps.filterd (ppma11.dal12v.mail.ibm.com [127.0.0.1]) by ppma11.dal12v.mail.ibm.com (8.18.1.2/8.18.1.2) with ESMTP id 5B1GQhmB029343; Mon, 1 Dec 2025 18:32:09 GMT Received: from smtprelay04.fra02v.mail.ibm.com ([9.218.2.228]) by ppma11.dal12v.mail.ibm.com (PPS) with ESMTPS id 4ardv17t8w-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 01 Dec 2025 18:32:09 +0000 Received: from smtpav03.fra02v.mail.ibm.com (smtpav03.fra02v.mail.ibm.com [10.20.54.102]) by smtprelay04.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 5B1IW7Ys15532388 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 1 Dec 2025 18:32:07 GMT Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5B1BB20043; Mon, 1 Dec 2025 18:32:07 +0000 (GMT) Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7AF6B20040; Mon, 1 Dec 2025 18:32:04 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.124.221.183]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 1 Dec 2025 18:32:04 +0000 (GMT) From: Shrikanth Hegde To: mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, kprateek.nayak@amd.com Cc: sshegde@linux.ibm.com, dietmar.eggemann@arm.com, vschneid@redhat.com, rostedt@goodmis.org, tglx@linutronix.de, tim.c.chen@linux.intel.com Subject: [PATCH 1/4] sched/fair: Move checking for nohz cpus after time check Date: Tue, 2 Dec 2025 00:01:43 +0530 Message-ID: <20251201183146.74443-2-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251201183146.74443-1-sshegde@linux.ibm.com> References: <20251201183146.74443-1-sshegde@linux.ibm.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-TM-AS-GCONF: 00 X-Proofpoint-GUID: -H7BarcusuyQ7M7qOS3ryFtYeP5Y4mEv X-Proofpoint-ORIG-GUID: -H7BarcusuyQ7M7qOS3ryFtYeP5Y4mEv X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTI5MDAyMCBTYWx0ZWRfX6bV5ocSY2qJs kNRaDo96teP6Oj6rSFC31YbBh73t+2+BL8ybVKjNK0cjnXImSIXl2GzC4N2zaFEWq8P5vlFBPJy Iel4hhZr1BPrNiCkw8CTGDz0/y+r8RxWWuln+7TVOnNQMqLD8+In+3d94xWotm36FUGuoCh7/b7 +o1T+4UgUDwQ1ANDdD9ZBGHA3orXzP7ML9o/VgtkBlNfCvTZJwiFu767VWSaunKvkSDXXyQk9tJ odLV7mSjxus2Gu286G3felssECqJy/E7TXgXijl5eqzLG+F+7iBUQnpuGLwZq/tIfPpMf1qymuL jvQ3vwjJs76iLY5FbXKzN863H9stYLkw1h7vZMvcQI3ZMmbmZZYvIHlcNWunka3D1OkGypeGzm6 5X8n2uaY4d7hv5qlSwbnWsMPuJMzDA== X-Authority-Analysis: v=2.4 cv=dYGNHHXe c=1 sm=1 tr=0 ts=692ddf2a cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=wP3pNCr1ah4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=OUFfOgFxQ-4zh-9IuIYA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-28_08,2025-11-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 suspectscore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 bulkscore=0 phishscore=0 priorityscore=1501 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511290020 Content-Type: text/plain; charset="utf-8" Idle load balancer is kicked off only after time check. So move the atomic read after the time check. If there are no nohz CPUs there likely has_blocked should be reset too. So stats load balancing shouldn't much difference.=20 Signed-off-by: Shrikanth Hegde =20 --- kernel/sched/fair.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 769d7b7990df..61cc3fdfa45b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12440,19 +12440,18 @@ static void nohz_balancer_kick(struct rq *rq) */ nohz_balance_exit_idle(rq); =20 - /* - * None are in tickless mode and hence no need for NOHZ idle load - * balancing: - */ - if (likely(!atomic_read(&nohz.nr_cpus))) - return; - if (READ_ONCE(nohz.has_blocked) && time_after(now, READ_ONCE(nohz.next_blocked))) flags =3D NOHZ_STATS_KICK; =20 if (time_before(now, nohz.next_balance)) goto out; + /* + * None are in tickless mode and hence no need for NOHZ idle load + * balancing: + */ + if (likely(!atomic_read(&nohz.nr_cpus))) + return; =20 if (rq->nr_running >=3D 2) { flags =3D NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; --=20 2.43.0