From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DB659C10F14 for ; Thu, 3 Oct 2019 17:15:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE12920673 for ; Thu, 3 Oct 2019 17:15:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570122908; bh=VR7Qr2sSZDvvWUGGowSu7a6WGDqx1uqcGdlqRG8+qwM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PEFDoc9P+vTJ2VN3JSNFLn6v/6htQlLwEltGDnWZCpaRNsEL5KlIVH7HkiHlo/cD7 CYgsO3Dpx8QLYObVNQP0cvNrrZuZFJDNdesP8vXKIkhtwFApLQx/rGYXNfxKH0WRbQ LZQf/s5GmHYLjYuARGQ5AZdQEu1PwQZ2Obe20Q6I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403887AbfJCRPE (ORCPT ); Thu, 3 Oct 2019 13:15:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:57472 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391063AbfJCQ0X (ORCPT ); Thu, 3 Oct 2019 12:26:23 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0F2D120867; Thu, 3 Oct 2019 16:26:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570119982; bh=VR7Qr2sSZDvvWUGGowSu7a6WGDqx1uqcGdlqRG8+qwM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U+//bAofW5n3o0eTLRKEah11ljQrVsLxl+VtdIQz9T1sezcxCiM29VBU/2n6GSICN UHT6eGzZR4Zk0p2mj6y7eTKwV63T96QsMqerQu6HvCnRFcPwxC9sJ2IVVgzPnbhsrA QV1n2zsn9OFx5Kk2G1hpxBeJl/tJ9En/nfHhe3sg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vincent Guittot , "Peter Zijlstra (Intel)" , Linus Torvalds , Thomas Gleixner , Ingo Molnar , Sasha Levin Subject: [PATCH 5.2 054/313] sched/fair: Fix imbalance due to CPU affinity Date: Thu, 3 Oct 2019 17:50:32 +0200 Message-Id: <20191003154538.389857532@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191003154533.590915454@linuxfoundation.org> References: <20191003154533.590915454@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Vincent Guittot [ Upstream commit f6cad8df6b30a5d2bbbd2e698f74b4cafb9fb82b ] The load_balance() has a dedicated mecanism to detect when an imbalance is due to CPU affinity and must be handled at parent level. In this case, the imbalance field of the parent's sched_group is set. The description of sg_imbalanced() gives a typical example of two groups of 4 CPUs each and 4 tasks each with a cpumask covering 1 CPU of the first group and 3 CPUs of the second group. Something like: { 0 1 2 3 } { 4 5 6 7 } * * * * But the load_balance fails to fix this UC on my octo cores system made of 2 clusters of quad cores. Whereas the load_balance is able to detect that the imbalanced is due to CPU affinity, it fails to fix it because the imbalance field is cleared before letting parent level a chance to run. In fact, when the imbalance is detected, the load_balance reruns without the CPU with pinned tasks. But there is no other running tasks in the situation described above and everything looks balanced this time so the imbalance field is immediately cleared. The imbalance field should not be cleared if there is no other task to move when the imbalance is detected. Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/1561996022-28829-1-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index b07672e793a81..f72bf8122fe4e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9319,9 +9319,10 @@ static int load_balance(int this_cpu, struct rq *this_rq, out_balanced: /* * We reach balance although we may have faced some affinity - * constraints. Clear the imbalance flag if it was set. + * constraints. Clear the imbalance flag only if other tasks got + * a chance to move and fix the imbalance. */ - if (sd_parent) { + if (sd_parent && !(env.flags & LBF_ALL_PINNED)) { int *group_imbalance = &sd_parent->groups->sgc->imbalance; if (*group_imbalance) -- 2.20.1