From nobody Tue Jun 30 04:38:09 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 31F1AC433EF for ; Tue, 25 Jan 2022 08:38:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378880AbiAYIiC (ORCPT ); Tue, 25 Jan 2022 03:38:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38666 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1450719AbiAYIdN (ORCPT ); Tue, 25 Jan 2022 03:33:13 -0500 Received: from mail-pl1-x62f.google.com (mail-pl1-x62f.google.com [IPv6:2607:f8b0:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2B4EEC0612AF for ; Mon, 24 Jan 2022 22:57:18 -0800 (PST) Received: by mail-pl1-x62f.google.com with SMTP id d1so18303976plh.10 for ; Mon, 24 Jan 2022 22:57:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:subject:date:message-id; bh=BCtqKKKae1nbJrnhJrOTwrukfpxsmoJefws7zuhcAHw=; b=SSF72/QjjYdyWJdBXKYhYAc8iQHn5Y8zWNSlDi9SMHxnF4VLhtwGVXfqxwNBdantFd L0VliNgqgt1dRmPK7YvWx2eZf4W3iYHMDRgfxa5qYShBhSRJEj7ZcFuv/vp2MUXyygYB qwrvhfSB9pD/rxwAydIzj3jIymkNMMhB2vseOArds+jRlk9CahLSkA0MYJlWExOPH1+u px385Af+ZE3Fq4JQGkeWCpIF+1KCFSZoBYnSbugtS5WG7khPHl19/XQohFJ4oz6Xiq5Z j7n7sZW4x4oj/3PXfSH/EGrCWNcgg0rpnNBG9TcVlDprFqSmJFbvoUZRpY/cRSG/ebyd byDA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:subject:date:message-id; bh=BCtqKKKae1nbJrnhJrOTwrukfpxsmoJefws7zuhcAHw=; b=dgjeyu7+1cJ5tMiK4rIHg7GUIAD/3LTUeR/ZskJkbakDU8DYxtKwdqjRsP36cgKN0B JKotLhs2I33I5qyiFkEWZGAkEk5ZNuhZh6akJm7MnmKmEPHyHMh16vbLorQOKonqKBkl CIQhBEmOcBt5oNE/FkrQ88v981RoWCxokW9hAidXCrh9QvBTkMT48YANgYXyB/M7JUVe i8fDys0gfS8lgSfFjD2FukZ3hHqolTJHE1DFaoGcsWYI2nFzE5r2e+BSN4bW71pmIuxK PTkoJ//IPQ3+Rv77H87VhuwuZiT8xFJuCMNAYzZr0wNdMX7sH4a7fwYLV7EsaqnN2oZE k38A== X-Gm-Message-State: AOAM532Li5hLOto9WTvvsuOzxwO/Y9p3bPrx5l6D8O435457zkGZKAm5 eUwbu+oLYOu9d6VjdEU/Y8g= X-Google-Smtp-Source: ABdhPJx0nX+TrHs0Ymc7uNiOGdLtM+qgjTddinHZrO8cpYA+uKxfTQvhvGCPnU+OsALRyc7mEO+bxQ== X-Received: by 2002:a17:902:e5c5:b0:14b:1bbb:9f5 with SMTP id u5-20020a170902e5c500b0014b1bbb09f5mr16983715plf.62.1643093837548; Mon, 24 Jan 2022 22:57:17 -0800 (PST) Received: from bj03382pcu.spreadtrum.com ([117.18.48.102]) by smtp.gmail.com with ESMTPSA id o18sm18941565pfu.45.2022.01.24.22.57.13 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 24 Jan 2022 22:57:16 -0800 (PST) From: Huangzhaoyang To: Johannes Weiner , Suren Baghdasaryan , Peter Zijlstra , Zhaoyang Huang , Ingo Molnar , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCHv4] psi: fix possible trigger missing in the window Date: Tue, 25 Jan 2022 14:56:58 +0800 Message-Id: <1643093818-19835-1-git-send-email-huangzhaoyang@gmail.com> X-Mailer: git-send-email 1.7.9.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Zhaoyang Huang 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 --- v2: modify the logic according to Suren's suggestion v3: update commit message v4: update variable name and comments --- --- 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 0a23300..e0ec129 100644 --- a/include/linux/psi_types.h +++ b/include/linux/psi_types.h @@ -132,6 +132,9 @@ 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 1652f2b..dd80bd2 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -515,7 +515,7 @@ 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 /* @@ -524,24 +524,35 @@ 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; @@ -550,9 +561,11 @@ 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 @@ -1152,6 +1165,7 @@ 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 --=20 1.9.1