From nobody Sun Jun 28 00:11:14 2026 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 E3AD9C433F5 for ; Thu, 17 Feb 2022 18:57:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244794AbiBQS51 (ORCPT ); Thu, 17 Feb 2022 13:57:27 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:38854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235762AbiBQS5K (ORCPT ); Thu, 17 Feb 2022 13:57:10 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F1B05D668; Thu, 17 Feb 2022 10:56:54 -0800 (PST) Date: Thu, 17 Feb 2022 18:56:51 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1645124212; 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=MBMvQsiG2NvPPtzi/hVREDQBmKieIMZ8/hnkIeo5qAI=; b=m5aicU8ilSs0PYwuPDPEWtL4fVvhC63oaoBwSdgHwLAIxYj9kQ7d8HwFCEsS6sLdqrQWps zyIuo8AI/EcNVe8NpFwX2xc7Gs7j8Yc2gFMZBBVO8j7aGgOUn1MQm6Tag5zDmRmwfwe6RJ 8gQl73OXVhyWZxWsoFDyys8kn3XqdkZZvmOZTktAXTRG3GvUmDGvC0drEC60G0L4U5dvvE fmhTGKWkxgdrhnKKGtp2N09lkPlBUJCypiNHo+R/JW8BEO4ik17X8gwMTBlWCOwt7JLKz/ 5J8igOdGszXViTzaynSjUAxRFd4C+HUYrWx3Ngj2KkrmBenoVbb8WAkIgJZCoQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1645124212; 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=MBMvQsiG2NvPPtzi/hVREDQBmKieIMZ8/hnkIeo5qAI=; b=GlTioHL4Z0gYLex3RV2RAxab5XgKvWZ9gRg0MbTtMIf7MOC20Pa3+jg7ZlyLY55GA0JPhP tBK8n4URjEZpo+Dg== From: "tip-bot2 for Zhaoyang Huang" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] psi: fix possible trigger missing in the window Cc: Suren Baghdasaryan , Zhaoyang Huang , "Peter Zijlstra (Intel)" , Johannes Weiner , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <1643093818-19835-1-git-send-email-huangzhaoyang@gmail.com> References: <1643093818-19835-1-git-send-email-huangzhaoyang@gmail.com> MIME-Version: 1.0 Message-ID: <164512421171.16921.5147262447831853726.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: e6df4ead85d9da1b07dd40bd4c6d2182f3e210c4 Gitweb: https://git.kernel.org/tip/e6df4ead85d9da1b07dd40bd4c6d2182f= 3e210c4 Author: Zhaoyang Huang AuthorDate: Tue, 25 Jan 2022 14:56:58 +08:00 Committer: Peter Zijlstra CommitterDate: Wed, 16 Feb 2022 15:57:54 +01:00 psi: fix possible trigger missing in the window When a new threshold breaching stall happens after a psi event was generated and within the window duration, the new event is not generated because the events are rate-limited to one per window. If after that no new stall is recorded then the event will not be generated even after rate-limiting duration has passed. This is happening because with no new stall, window_update will not be called even though threshold was previously breached. To fix this, record threshold breaching occurrence and generate the event once window duration is passed. Suggested-by: Suren Baghdasaryan Signed-off-by: Zhaoyang Huang Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Acked-by: Suren Baghdasaryan Link: https://lore.kernel.org/r/1643093818-19835-1-git-send-email-huangzhao= yang@gmail.com --- include/linux/psi_types.h | 3 ++- kernel/sched/psi.c | 46 ++++++++++++++++++++++++-------------- 2 files changed, 33 insertions(+), 16 deletions(-) diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h index 516c0fe..dc3ec5e 100644 --- a/include/linux/psi_types.h +++ b/include/linux/psi_types.h @@ -144,6 +144,9 @@ struct psi_trigger { =20 /* Refcounting to prevent premature destruction */ struct kref refcount; + + /* Deferred event(s) from previous ratelimit window */ + bool pending_event; }; =20 struct psi_group { diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index cfe76f7..e9d623c 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -523,7 +523,7 @@ static void init_triggers(struct psi_group *group, u64 = now) static u64 update_triggers(struct psi_group *group, u64 now) { struct psi_trigger *t; - bool new_stall =3D false; + bool update_total =3D false; u64 *total =3D group->total[PSI_POLL]; =20 /* @@ -532,24 +532,35 @@ static u64 update_triggers(struct psi_group *group, u= 64 now) */ list_for_each_entry(t, &group->triggers, node) { u64 growth; + bool new_stall; =20 - /* Check for stall activity */ - if (group->polling_total[t->state] =3D=3D total[t->state]) - continue; + new_stall =3D group->polling_total[t->state] !=3D total[t->state]; =20 + /* Check for stall activity or a previous threshold breach */ + if (!new_stall && !t->pending_event) + continue; /* - * Multiple triggers might be looking at the same state, - * remember to update group->polling_total[] once we've - * been through all of them. Also remember to extend the - * polling time if we see new stall activity. + * Check for new stall activity, as well as deferred + * events that occurred in the last window after the + * trigger had already fired (we want to ratelimit + * events without dropping any). */ - new_stall =3D true; - - /* Calculate growth since last update */ - growth =3D window_update(&t->win, now, total[t->state]); - if (growth < t->threshold) - continue; - + if (new_stall) { + /* + * Multiple triggers might be looking at the same state, + * remember to update group->polling_total[] once we've + * been through all of them. Also remember to extend the + * polling time if we see new stall activity. + */ + update_total =3D true; + + /* Calculate growth since last update */ + growth =3D window_update(&t->win, now, total[t->state]); + if (growth < t->threshold) + continue; + + t->pending_event =3D true; + } /* Limit event signaling to once per window */ if (now < t->last_event_time + t->win.size) continue; @@ -558,9 +569,11 @@ static u64 update_triggers(struct psi_group *group, u6= 4 now) if (cmpxchg(&t->event, 0, 1) =3D=3D 0) wake_up_interruptible(&t->event_wait); t->last_event_time =3D now; + /* Reset threshold breach flag once event got generated */ + t->pending_event =3D false; } =20 - if (new_stall) + if (update_total) memcpy(group->polling_total, total, sizeof(group->polling_total)); =20 @@ -1125,6 +1138,7 @@ struct psi_trigger *psi_trigger_create(struct psi_gro= up *group, t->last_event_time =3D 0; init_waitqueue_head(&t->event_wait); kref_init(&t->refcount); + t->pending_event =3D false; =20 mutex_lock(&group->trigger_lock); =20