From nobody Thu Dec 18 15:24:27 2025 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 5E56CCDB47E for ; Wed, 18 Oct 2023 15:51:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232182AbjJRPvq (ORCPT ); Wed, 18 Oct 2023 11:51:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232279AbjJRPvj (ORCPT ); Wed, 18 Oct 2023 11:51:39 -0400 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8F3F2118 for ; Wed, 18 Oct 2023 08:51:37 -0700 (PDT) Received: from pps.filterd (m0353723.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 39IFnbhj010839; Wed, 18 Oct 2023 15:51:11 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding; s=pp1; bh=YqEAXhIbrZO4p/9m5sqSlbZgv6nkuUCB6eyMpurijrg=; b=FWq+jFkDCm5XlUxZ+WLQAHhcKEYpE4VA1NdAlT3+x52dt0uC3qmiC5+nZzXblNyb6sT/ IBb8GkvTLMa8UGjz3WrO3+gHKSymFNWo2fl5LqObNuXvS+VWAS8g7B6wGWpz04YP5YwT 3r5UNUKUoEJEDADF7yBydmT3Z+KkNUskm5OC7N6zslmqqGmJ/c/PhoklgqlnAcPFiPE6 1N10szAakH6TaAxb/oQ0qHB4J1h6fuHOIa8nKlIJDLm9tBOLdqfeTEo2qmzQn65eQMJh DjUVhoyzpANGRomA2B7iegVFx6jhdENylwqblTnGFNaaL/Sin8jOU/f9Bh39Tlozt/R4 pw== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3ttjbg02hs-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 18 Oct 2023 15:51:10 +0000 Received: from m0353723.ppops.net (m0353723.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 39IFnmAZ011098; Wed, 18 Oct 2023 15:51:10 GMT Received: from ppma13.dal12v.mail.ibm.com (dd.9e.1632.ip4.static.sl-reverse.com [50.22.158.221]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3ttjbg02eg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 18 Oct 2023 15:51:10 +0000 Received: from pps.filterd (ppma13.dal12v.mail.ibm.com [127.0.0.1]) by ppma13.dal12v.mail.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 39IFnLFS031142; Wed, 18 Oct 2023 15:51:07 GMT Received: from smtprelay02.fra02v.mail.ibm.com ([9.218.2.226]) by ppma13.dal12v.mail.ibm.com (PPS) with ESMTPS id 3tr7hjsa6j-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 18 Oct 2023 15:51:07 +0000 Received: from smtpav04.fra02v.mail.ibm.com (smtpav04.fra02v.mail.ibm.com [10.20.54.103]) by smtprelay02.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 39IFp6Fx15925890 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 18 Oct 2023 15:51:06 GMT Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 127932004F; Wed, 18 Oct 2023 15:51:06 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1598F20043; Wed, 18 Oct 2023 15:51:03 +0000 (GMT) Received: from sapthagiri.in.ibm.com (unknown [9.43.47.66]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 18 Oct 2023 15:51:02 +0000 (GMT) From: Srikar Dronamraju To: Ingo Molnar , Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider Cc: LKML , Srikar Dronamraju Subject: [PATCH] sched/fair: Enable group_asym_packing in find_idlest_group Date: Wed, 18 Oct 2023 21:20:35 +0530 Message-ID: <20231018155036.2314342-1-srikar@linux.vnet.ibm.com> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: DV-vLiv0mu1yWIaV3yrjhV5iCunaLvup X-Proofpoint-GUID: 0FNOajdg9yX1a1BNOmfNOV9nZiG7JcwF X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-10-18_14,2023-10-18_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 malwarescore=0 phishscore=0 impostorscore=0 clxscore=1011 priorityscore=1501 bulkscore=0 suspectscore=0 mlxscore=0 adultscore=0 spamscore=0 mlxlogscore=914 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000 definitions=main-2310180128 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Current scheduler code doesn't handle SD_ASYM_PACKING in the find_idlest_cpu path. On few architectures, like Powerpc, cache is at a core. Moving threads across cores may end up in cache misses. While asym_packing can be enabled above SMT level, enabling Asym packing across cores could result in poorer performance due to cache misses. However if the initial task placement via find_idlest_cpu does take Asym_packing into consideration, then scheduler can avoid asym_packing migrations. This will result in lesser migrations and better packing and better overall performance. Signed-off-by: Srikar Dronamraju --- kernel/sched/fair.c | 33 ++++++++++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index cb225921bbca..7164f79a3d13 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9931,11 +9931,13 @@ static int idle_cpu_without(int cpu, struct task_st= ruct *p) * @group: sched_group whose statistics are to be updated. * @sgs: variable to hold the statistics for this group. * @p: The task for which we look for the idlest group/CPU. + * @this_cpu: current cpu */ static inline void update_sg_wakeup_stats(struct sched_domain *sd, struct sched_group *group, struct sg_lb_stats *sgs, - struct task_struct *p) + struct task_struct *p, + int this_cpu) { int i, nr_running; =20 @@ -9972,6 +9974,11 @@ static inline void update_sg_wakeup_stats(struct sch= ed_domain *sd, =20 } =20 + if (sd->flags & SD_ASYM_PACKING && sgs->sum_h_nr_running && + sched_asym_prefer(group->asym_prefer_cpu, this_cpu)) { + sgs->group_asym_packing =3D 1; + } + sgs->group_capacity =3D group->sgc->capacity; =20 sgs->group_weight =3D group->group_weight; @@ -10012,8 +10019,17 @@ static bool update_pick_idlest(struct sched_group = *idlest, return false; break; =20 - case group_imbalanced: case group_asym_packing: + if (sched_asym_prefer(group->asym_prefer_cpu, idlest->asym_prefer_cpu)) { + int busy_cpus =3D idlest_sgs->group_weight - idlest_sgs->idle_cpus; + + busy_cpus -=3D (sgs->group_weight - sgs->idle_cpus); + if (busy_cpus >=3D 0) + return true; + } + return false; + + case group_imbalanced: case group_smt_balance: /* Those types are not used in the slow wakeup path */ return false; @@ -10080,7 +10096,7 @@ find_idlest_group(struct sched_domain *sd, struct t= ask_struct *p, int this_cpu) sgs =3D &tmp_sgs; } =20 - update_sg_wakeup_stats(sd, group, sgs, p); + update_sg_wakeup_stats(sd, group, sgs, p, this_cpu); =20 if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs))= { idlest =3D group; @@ -10112,6 +10128,17 @@ find_idlest_group(struct sched_domain *sd, struct = task_struct *p, int this_cpu) if (local_sgs.group_type > idlest_sgs.group_type) return idlest; =20 + if (idlest_sgs.group_type =3D=3D group_asym_packing) { + if (sched_asym_prefer(idlest->asym_prefer_cpu, local->asym_prefer_cpu)) { + int busy_cpus =3D local_sgs.group_weight - local_sgs.idle_cpus; + + busy_cpus -=3D (idlest_sgs.group_weight - idlest_sgs.idle_cpus); + if (busy_cpus >=3D 0) + return idlest; + } + return NULL; + } + switch (local_sgs.group_type) { case group_overloaded: case group_fully_busy: --=20 2.31.1