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 X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C99D9C07E97 for ; Sat, 3 Jul 2021 17:29:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5CE661930 for ; Sat, 3 Jul 2021 17:29:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229847AbhGCRcW (ORCPT ); Sat, 3 Jul 2021 13:32:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55942 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229463AbhGCRcV (ORCPT ); Sat, 3 Jul 2021 13:32:21 -0400 Received: from mail-ed1-x52b.google.com (mail-ed1-x52b.google.com [IPv6:2a00:1450:4864:20::52b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3845C061762 for ; Sat, 3 Jul 2021 10:29:47 -0700 (PDT) Received: by mail-ed1-x52b.google.com with SMTP id y40so2590990ede.4 for ; Sat, 03 Jul 2021 10:29:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=anisinha-ca.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=c9Iem/lMag2RPHwMZ9nBzIAPE7ruGDDVMReqojOyreo=; b=IxlnDe2lJwZtAR4ELgMRJoHTJjujG0dQrYQbmyVSGmQKZfZuFWkLX2jyQ6h2nP8fwP a8o1BqCJcZjJUPRRVxrySwvLh9HDVzjjYugLf0phIpziWJXGGo1E9D8jOBPh6QAMDCsI uPWXzZdVX7C+D4bVeFp307aOi3EkDl5NXx3iPwb8ZgMdkMOFRqhP2PHmPwG43Pxptujm KeUb2tpeq7rTINg2QNP2Ihp7SQEKoMhLOA1wLN55gR0qxIWF8SlB6+aSRuuvMdnfeFfK GKBlffmnbjht6i5Xy4n8Q6oasrVwiRoZNLfjkJVa1mgQOMLFRlPs4x+RQUpMSDMW4FRo ew3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=c9Iem/lMag2RPHwMZ9nBzIAPE7ruGDDVMReqojOyreo=; b=djjy3tFd1wGabWCAr9U/ttXPP0sk7H3kGo9lXZRe9KIivEY4+aWduMEUUaZKgf6lsc CkJM/uHncKxoQ72sC79+DsTDOGNm+GMsBrdT86PPg+skEdVWcMSqBco5C1Mf431ZoJIU RVPmdU5jyZtwPYUK4HjqL4y614cENQ2TFLnqniWczSw4DIyN/nJQ+43CQK4UHrGU27I5 SV+89aPlzSsXemW/gPkBeVRyK5acJ0RZUZ5kj6sXR15jNGhRjgFZYaZ+EbBRN9lqeIE9 Oea6QShkHvaWGZvQ251U0G9v8lrIxLZZqn7q0QfbDjxHjKQ2OR8gHEqA3V6YeqkJVd7w oDPQ== X-Gm-Message-State: AOAM530VucmMZJ/6zBmaELY/hZgnu3Ju73aDM6fV+Zb7K7YrDgCRE2QW D+TUqc1xMikGgrnEbkzailM2kq5ueU+vrDX8Xy8LMyjDM/U= X-Google-Smtp-Source: ABdhPJyYFlHs7cjbwLH0Stf4MCif/zWZykYcyHD0iQq1ImnAHQa50S+a7mWEFwaQsAMKWZrxC0i8PjpVrxEET9++2kk= X-Received: by 2002:aa7:cb03:: with SMTP id s3mr6291730edt.189.1625333386227; Sat, 03 Jul 2021 10:29:46 -0700 (PDT) MIME-Version: 1.0 References: <20210627072833.2199463-1-ani@anisinha.ca> In-Reply-To: <20210627072833.2199463-1-ani@anisinha.ca> From: Ani Sinha Date: Sat, 3 Jul 2021 22:59:35 +0530 Message-ID: Subject: Re: [PATCH v1] Add info log when user enables NOHZ in commandline but NOHZ is not possible To: linux-kernel@vger.kernel.org Cc: anirban.sinha@nokia.com, Thomas Gleixner , Frederic Weisbecker , Ingo Molnar Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ping ... On Sun, Jun 27, 2021 at 12:58 PM Ani Sinha wrote: > > Commit 4f49b90abb4aca ("sched-clock: Migrate to use new tick > dependency mask model") had also removed the kernel warning > message informing the user that it was not possible to turn > on NO_HZ_FULL. This warning was added in commit e12d0271774fe > ("nohz: Warn if the machine can not perform nohz_full") in order > to warn users when they enabled NOHZ using the kernel commandline > but kernel could not enable NOHZ. Removal of this log defeats this > purpose because we still do not want users thinking that they are > getting the benefit of nohz when their machine can not support it. > Hence this patch brings back the information log. > > If at some point the conditions that prevented NOHZ from being > enabled goes away and the previous info log was printed, we print > another log informing the user that NOHZ was again possible. > > Signed-off-by: Ani Sinha > --- > kernel/time/tick-sched.c | 21 ++++++++++++++++++--- > 1 file changed, 18 insertions(+), 3 deletions(-) > > See also thread: https://lkml.org/lkml/2021/6/20/32 > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index 828b091501ca..fbef95b57b1d 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -930,6 +930,7 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts) > { > #ifdef CONFIG_NO_HZ_FULL > int cpu = smp_processor_id(); > + static bool no_tick_warned; > > if (!tick_nohz_full_cpu(cpu)) > return; > @@ -937,10 +938,24 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts) > if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) > return; > > - if (can_stop_full_tick(cpu, ts)) > + if (can_stop_full_tick(cpu, ts)) { > tick_nohz_stop_sched_tick(ts, cpu); > - else if (ts->tick_stopped) > - tick_nohz_restart_sched_tick(ts, ktime_get()); > + if (no_tick_warned) { > + pr_info("NO_HZ_FULL is now enabled in the system.\n"); > + no_tick_warned = false; > + } > + } else { > + /* > + * Don't allow the user to think they can get > + * full NO_HZ with this machine. > + */ > + if (!no_tick_warned && tick_nohz_full_running) { > + pr_info("NO_HZ_FULL has been disabled in the system."); > + no_tick_warned = true; > + } > + if (ts->tick_stopped) > + tick_nohz_restart_sched_tick(ts, ktime_get()); > + } > #endif > } > > -- > 2.25.1 >