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[2620:137:e000::1:20]) by mx.google.com with ESMTP id gk6-20020a17090790c600b0088c98150395si615953ejb.433.2023.02.11.02.38.58; Sat, 11 Feb 2023 02:39:21 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=X2RJ+HJ1; dkim=neutral (no key) header.i=@linutronix.de header.s=2020e header.b=ygGh37fT; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229963AbjBKKbB (ORCPT + 99 others); Sat, 11 Feb 2023 05:31:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229762AbjBKKa4 (ORCPT ); Sat, 11 Feb 2023 05:30:56 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 042DA2197F; Sat, 11 Feb 2023 02:30:56 -0800 (PST) Date: Sat, 11 Feb 2023 10:30:54 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1676111454; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=rmdPyDM+tz9rqCjEuFxQxMiI/xnQqO9uZI+vZtzn3Wk=; b=X2RJ+HJ1WB/o9LsLjk5UpoikHGHsiOe95xxcU4MNZCNBydle+Idg0S8Bg39uYdO97kKvaA ihSx6E1D9ekBJak8kuBN/p3wL59VzKtpFCyG71uuHhU5Ok5wOImL9aanY1+nUMM8UgWOBB sHLpFMYffqj2T7boEFik8FXNpZUbr00IOX1a6oS/H4lmnDveBtbX+sre6FlZNSIB2HcJck JDm/SNf8uUlyLytqEuD+w0QkeC4+IkWBTwNEtJFlYAEDa7nvxgmc1Wtai4lB32b/LV4Hzh OfiW+J5WF6ZE2EsV0eg7ulOxxzBqrVnQlIUuFdWtNzEnLbBPVCWpZZpMrsfYng== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1676111454; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=rmdPyDM+tz9rqCjEuFxQxMiI/xnQqO9uZI+vZtzn3Wk=; b=ygGh37fT/U8VUfzwN02SQL2XQczNcXlTzUNXmMloRz8kEAtKoOLRhY5m4tyZmAN9W0JPtN xgDvr4ej7m7UG7Bw== From: "tip-bot2 for Zhang Qiao" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/fair: sanitize vruntime of entity being placed Cc: Zhang Qiao , Roman Kagan , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230130122216.3555094-1-rkagan@amazon.de> References: <20230130122216.3555094-1-rkagan@amazon.de> MIME-Version: 1.0 Message-ID: <167611145417.4906.10757655452818382605.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1756450645922962580?= X-GMAIL-MSGID: =?utf-8?q?1757530775831465025?= The following commit has been merged into the sched/core branch of tip: Commit-ID: 829c1651e9c4a6f78398d3e67651cef9bb6b42cc Gitweb: https://git.kernel.org/tip/829c1651e9c4a6f78398d3e67651cef9bb6b42cc Author: Zhang Qiao AuthorDate: Mon, 30 Jan 2023 13:22:16 +01:00 Committer: Peter Zijlstra CommitterDate: Sat, 11 Feb 2023 11:18:09 +01:00 sched/fair: sanitize vruntime of entity being placed When a scheduling entity is placed onto cfs_rq, its vruntime is pulled to the base level (around cfs_rq->min_vruntime), so that the entity doesn't gain extra boost when placed backwards. However, if the entity being placed wasn't executed for a long time, its vruntime may get too far behind (e.g. while cfs_rq was executing a low-weight hog), which can inverse the vruntime comparison due to s64 overflow. This results in the entity being placed with its original vruntime way forwards, so that it will effectively never get to the cpu. To prevent that, ignore the vruntime of the entity being placed if it didn't execute for much longer than the characteristic sheduler time scale. [rkagan: formatted, adjusted commit log, comments, cutoff value] Signed-off-by: Zhang Qiao Co-developed-by: Roman Kagan Signed-off-by: Roman Kagan Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230130122216.3555094-1-rkagan@amazon.de --- kernel/sched/fair.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c6c8e7f..ff4dbba 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4652,6 +4652,7 @@ static void place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) { u64 vruntime = cfs_rq->min_vruntime; + u64 sleep_time; /* * The 'current' period is already promised to the current tasks, @@ -4681,8 +4682,18 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) vruntime -= thresh; } - /* ensure we never gain time by being placed backwards. */ - se->vruntime = max_vruntime(se->vruntime, vruntime); + /* + * Pull vruntime of the entity being placed to the base level of + * cfs_rq, to prevent boosting it if placed backwards. If the entity + * slept for a long time, don't even try to compare its vruntime with + * the base as it may be too far off and the comparison may get + * inversed due to s64 overflow. + */ + sleep_time = rq_clock_task(rq_of(cfs_rq)) - se->exec_start; + if ((s64)sleep_time > 60LL * NSEC_PER_SEC) + se->vruntime = vruntime; + else + se->vruntime = max_vruntime(se->vruntime, vruntime); } static void check_enqueue_throttle(struct cfs_rq *cfs_rq);