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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C928C433EF for ; Tue, 7 Jun 2022 18:28:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351171AbiFGS2l (ORCPT ); Tue, 7 Jun 2022 14:28:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51588 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351410AbiFGSQU (ORCPT ); Tue, 7 Jun 2022 14:16:20 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C543815FE00; Tue, 7 Jun 2022 10:49:32 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9DDBB6172E; Tue, 7 Jun 2022 17:49:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FAB5C385A5; Tue, 7 Jun 2022 17:49:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1654624162; bh=fNkJkBOthq+LhW72L2cl/PpwrwQpCtvNTh0mCjjeWfk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bBOchRv/YT4yHY/xFcAEH/tYHxOASma8KZHuaXYVYGYHqYHDnQjB6ESMjh5VdpmzY hdTrTuWDsOZLGZwyP/MTADigVikOW7jo17e3d5lyUQlkItjCjL75zqkvuyuefw+VJo rj0H74BlZJRkj/AxM8o5gJySB35Hig02i6eacqVg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Martin Steigerwald , Johannes Weiner , Chengming Zhou , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 5.15 228/667] sched/psi: report zeroes for CPU full at the system level Date: Tue, 7 Jun 2022 18:58:13 +0200 Message-Id: <20220607164941.628049082@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220607164934.766888869@linuxfoundation.org> References: <20220607164934.766888869@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Chengming Zhou [ Upstream commit 890d550d7dbac7a31ecaa78732aa22be282bb6b8 ] Martin find it confusing when look at the /proc/pressure/cpu output, and found no hint about that CPU "full" line in psi Documentation. % cat /proc/pressure/cpu some avg10=0.92 avg60=0.91 avg300=0.73 total=933490489 full avg10=0.22 avg60=0.23 avg300=0.16 total=358783277 The PSI_CPU_FULL state is introduced by commit e7fcd7622823 ("psi: Add PSI_CPU_FULL state"), which mainly for cgroup level, but also counted at the system level as a side effect. Naturally, the FULL state doesn't exist for the CPU resource at the system level. These "full" numbers can come from CPU idle schedule latency. For example, t1 is the time when task wakeup on an idle CPU, t2 is the time when CPU pick and switch to it. The delta of (t2 - t1) will be in CPU_FULL state. Another case all processes can be stalled is when all cgroups have been throttled at the same time, which unlikely to happen. Anyway, CPU_FULL metric is meaningless and confusing at the system level. So this patch will report zeroes for CPU full at the system level, and update psi Documentation accordingly. Fixes: e7fcd7622823 ("psi: Add PSI_CPU_FULL state") Reported-by: Martin Steigerwald Suggested-by: Johannes Weiner Signed-off-by: Chengming Zhou Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lore.kernel.org/r/20220408121914.82855-1-zhouchengming@bytedance.com Signed-off-by: Sasha Levin --- Documentation/accounting/psi.rst | 9 ++++----- kernel/sched/psi.c | 15 +++++++++------ 2 files changed, 13 insertions(+), 11 deletions(-) diff --git a/Documentation/accounting/psi.rst b/Documentation/accounting/psi.rst index 860fe651d645..5e40b3f437f9 100644 --- a/Documentation/accounting/psi.rst +++ b/Documentation/accounting/psi.rst @@ -37,11 +37,7 @@ Pressure interface Pressure information for each resource is exported through the respective file in /proc/pressure/ -- cpu, memory, and io. -The format for CPU is as such:: - - some avg10=0.00 avg60=0.00 avg300=0.00 total=0 - -and for memory and IO:: +The format is as such:: some avg10=0.00 avg60=0.00 avg300=0.00 total=0 full avg10=0.00 avg60=0.00 avg300=0.00 total=0 @@ -58,6 +54,9 @@ situation from a state where some tasks are stalled but the CPU is still doing productive work. As such, time spent in this subset of the stall state is tracked separately and exported in the "full" averages. +CPU full is undefined at the system level, but has been reported +since 5.13, so it is set to zero for backward compatibility. + The ratios (in %) are tracked as recent trends over ten, sixty, and three hundred second windows, which gives insight into short term events as well as medium and long term trends. The total absolute stall time diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 422f3b0445cf..cad2a1b34ed0 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -1062,14 +1062,17 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) mutex_unlock(&group->avgs_lock); for (full = 0; full < 2; full++) { - unsigned long avg[3]; - u64 total; + unsigned long avg[3] = { 0, }; + u64 total = 0; int w; - for (w = 0; w < 3; w++) - avg[w] = group->avg[res * 2 + full][w]; - total = div_u64(group->total[PSI_AVGS][res * 2 + full], - NSEC_PER_USEC); + /* CPU FULL is undefined at the system level */ + if (!(group == &psi_system && res == PSI_CPU && full)) { + for (w = 0; w < 3; w++) + avg[w] = group->avg[res * 2 + full][w]; + total = div_u64(group->total[PSI_AVGS][res * 2 + full], + NSEC_PER_USEC); + } seq_printf(m, "%s avg10=%lu.%02lu avg60=%lu.%02lu avg300=%lu.%02lu total=%llu\n", full ? "full" : "some", -- 2.35.1