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 D9263CCA483 for ; Tue, 7 Jun 2022 20:56:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377758AbiFGUzA (ORCPT ); Tue, 7 Jun 2022 16:55:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50080 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358850AbiFGTxR (ORCPT ); Tue, 7 Jun 2022 15:53:17 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 97F3DAE4D; Tue, 7 Jun 2022 11:22:43 -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 sin.source.kernel.org (Postfix) with ESMTPS id C6C1DCE2424; Tue, 7 Jun 2022 18:22:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ABE3BC385A2; Tue, 7 Jun 2022 18:22:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1654626160; bh=i0e136J9ViTHcA4OXA4kR6SgTxHZK4UV/2VaZhZrrnE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b265UFbh86mbqL57M6Jpa/7EZ4E2TieKFoYjbgiuIX5Al+XhTZqQPej2WCSReVPwt yBmLM4HxQhR+VV/JBp5/9FbLw/pZlmlD2yr7zC6KVxYIeB86z3Nl2lYcqn51mh+qG8 8GBitLzu2koxL7ObjuhRGeU3PeP9ombjGHOYVPvI= 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 5.17 279/772] sched/psi: report zeroes for CPU full at the system level Date: Tue, 7 Jun 2022 18:57:51 +0200 Message-Id: <20220607164957.247110666@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220607164948.980838585@linuxfoundation.org> References: <20220607164948.980838585@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: linux-kernel@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 e14358178849..97fd85c5143c 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