From patchwork Tue Jan 25 06:56:58 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhaoyang Huang X-Patchwork-Id: 12723334 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id F183AC433EF for ; Tue, 25 Jan 2022 06:57:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5F6596B0081; Tue, 25 Jan 2022 01:57:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5A5C16B0083; Tue, 25 Jan 2022 01:57:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 46CD66B0085; Tue, 25 Jan 2022 01:57:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0187.hostedemail.com [216.40.44.187]) by kanga.kvack.org (Postfix) with ESMTP id 36DD96B0081 for ; Tue, 25 Jan 2022 01:57:19 -0500 (EST) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id E38321842BE33 for ; Tue, 25 Jan 2022 06:57:18 +0000 (UTC) X-FDA: 79067902956.04.7C80490 Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) by imf30.hostedemail.com (Postfix) with ESMTP id 941FC80010 for ; Tue, 25 Jan 2022 06:57:18 +0000 (UTC) Received: by mail-pl1-f169.google.com with SMTP id y17so7961044plg.7 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=iQRKYwKSm/6K8HCvsyL0aNmnluNpO3Sv7SezbMHwuIprEP6QiOOuXaW7ZaqMRcJxK0 yoplK7SxrJs2vvjFlSyyzD2gucadVJzPYuY9uU3b4Ir8Mqwl1yVeDppb2XWGZuFU6Kjx qOJl9ye2pYhZHjFarNB8TQJWxco2YppMV0rP5aPAwkhHdgS3ZUrKCrMksaGOHHJeCJaL 7GpWkP5Mn/qyUqHwWY+hMG9RQzUB0wDflWghcrNj2b2/A4L8cvqydel/cDsWTrsPFiWY JuBl1qmkZarbK1F2qmKg4dEbeOw0iIzOkiQc22Maz9GzpflVBuSKtlk21YwMFUF5fPI9 j9jA== X-Gm-Message-State: AOAM530YSsQ9ztOybZ/VUfywzR5ljC0V1Jek4Qowa+Kv/GR70tQZMJ3a wFRdXItKg5wB3fp41AS4qDs= 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 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 941FC80010 X-Stat-Signature: 8isgn9f1urwied543x1atg5yek5ci7da Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="SSF72/Qj"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf30.hostedemail.com: domain of huangzhaoyang@gmail.com designates 209.85.214.169 as permitted sender) smtp.mailfrom=huangzhaoyang@gmail.com X-Rspam-User: nil X-HE-Tag: 1643093838-492347 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 Acked-by: Johannes Weiner Acked-by: Suren Baghdasaryan --- 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 { /* Refcounting to prevent premature destruction */ struct kref refcount; + + /* Deferred event(s) from previous ratelimit window */ + bool pending_event; }; 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 = false; + bool update_total = false; u64 *total = group->total[PSI_POLL]; /* @@ -524,24 +524,35 @@ static u64 update_triggers(struct psi_group *group, u64 now) */ list_for_each_entry(t, &group->triggers, node) { u64 growth; + bool new_stall; - /* Check for stall activity */ - if (group->polling_total[t->state] == total[t->state]) - continue; + new_stall = group->polling_total[t->state] != total[t->state]; + /* 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 = true; - - /* Calculate growth since last update */ - growth = 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 = true; + + /* Calculate growth since last update */ + growth = window_update(&t->win, now, total[t->state]); + if (growth < t->threshold) + continue; + + t->pending_event = 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, u64 now) if (cmpxchg(&t->event, 0, 1) == 0) wake_up_interruptible(&t->event_wait); t->last_event_time = now; + /* Reset threshold breach flag once event got generated */ + t->pending_event = false; } - if (new_stall) + if (update_total) memcpy(group->polling_total, total, sizeof(group->polling_total)); @@ -1152,6 +1165,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, t->last_event_time = 0; init_waitqueue_head(&t->event_wait); kref_init(&t->refcount); + t->pending_event = false; mutex_lock(&group->trigger_lock);