From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9159C2C11F0 for ; Tue, 16 Sep 2025 17:07:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758042472; cv=none; b=niWdXWSucqoTiD1Wj5KlAdQ55uPLe8XpXO+RyTvd0JNo2GFRAkaJ+OLVZ0fe+p7WouI3raRWNzUdZk83Sj+8M3vAECV9jEiDBfrrDliYkZZmhu0n0kXKgqm1/CIWRMT3dmBTUD8NcTmRgtjoYrXyxEvI+EmlCRlsa8BDqtDuwzM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758042472; c=relaxed/simple; bh=x4t62n6qoMGHUscwTZJIKGNpPN6wwdruLXh4XohgnEg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=F5soJBPdEJVWWO4yDmz2axYUd5sgYbdUMJ+trkfjKKckS5K9vb3L0h6Ifk1Atj9FE6b6mBErgwnjbTPt5xB52OUA4gJwQqZ9PtnynTs0mHVp/mSQoEBsPK3x0rJXq5/PJKsG4cW8K/rfMk7IrSLb11hClC5Aw1lVFRNSfVq/+M4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=U0oZprcg; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="U0oZprcg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758042469; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=G3KbOpCV6y4vZCLZsd26ud6uAmRpvckeE+th1wdyLDI=; b=U0oZprcgyozPppvfVZ6xd1sGVQPgQNIqEeotcjjTT0CIpP6jh33fB/fYa9p6vrNuSBHcwO g236DcmOOU2nGsFCDFT3iZBC/pTts+JtYC5sQoGlcXOhCjr2gq7E4EkYz4uU86AriGVERk t7C581tu7TGLngcwaAhWQtwqH20Ft/M= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-116-wH0zHu9tP0a9pF-lDN59bg-1; Tue, 16 Sep 2025 13:07:44 -0400 X-MC-Unique: wH0zHu9tP0a9pF-lDN59bg-1 X-Mimecast-MFC-AGG-ID: wH0zHu9tP0a9pF-lDN59bg_1758042462 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 146CC180047F; Tue, 16 Sep 2025 17:07:42 +0000 (UTC) Received: from pauld.westford.csb (unknown [10.22.65.67]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 51326300018D; Tue, 16 Sep 2025 17:07:38 +0000 (UTC) Date: Tue, 16 Sep 2025 13:07:35 -0400 From: Phil Auld To: Aaron Tomlin Cc: Michal =?iso-8859-1?Q?Koutn=FD?= , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, shashank.mahadasyam@sony.com, longman@redhat.com, tj@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/core: Report failed rt migrations to non-root cgroup without rt bandwidth under RT_GROUP_SCHED Message-ID: <20250916170735.GA5293@pauld.westford.csb> References: <20250916011146.4129696-1-atomlin@atomlin.com> <6zi6fp2kgs2hjychav3rrf22qwwskegdq53ew33tfn7rylueik@slugq2khaakw> <4nafhr4wqvta5uk4jfuxi7rc7fyaurflrfxa54ajaajy3o57mj@55qzh24m2u6s> <3emv4bx2o7mdv7oc72ffdinlltqohqjt5nxgccdiyw47xjgbww@drvkcpiy5zq5> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On Tue, Sep 16, 2025 at 12:57:04PM -0400 Aaron Tomlin wrote: > On Tue, Sep 16, 2025 at 05:44:14PM +0200, Michal Koutný wrote: > > On Tue, Sep 16, 2025 at 10:47:56AM -0400, Aaron Tomlin wrote: > > > I would prefer not to take any action. However, is there a strong > > > preference to demote the rt task so the CPU controller can be enabled in > > > this context? > > > > Maybe more context clarifies. The preference is not to end up in this > > corner. > > I see. If I understand correctly, in this context, are you suggesting to > modify the identified task's scheduling class (e.g. to SCHED_NORMAL) so the > CPU controller can be enabled? > > > I wonder does this combination come from a distro or is it your custom > > setup? I assume the latter (but I'm curious if there's such a distro), in > > that case you likely want to have the cpu controller on v1 hierarchy. v1 > > usage is what the boottime switch is currently useful for, v2 de facto > > doesn't support RT group scheduling as of today [1], v2 systems should > > simply unset CONFIG_RT_GROUP_SCHED to avoid issues enabling cpu > > controller. > > Yes. Under Red Hat Enterprise Linux (RHEL) 9 Kconfig option > CONFIG_RT_GROUP_SCHED and Cgroup version 2 is enabled by default. > Albeit, upstream can disable SCHED_FIFO/SCHED_RT group scheduling at > boot-time via rt_group_sched=. > CONFIG_RT_GROUP_SCHED is not enabled in RHEL9 and later. It was on in RHEL8 which also defaulted to cgroupv1. Thanks, Phil > > HTH, > > Michal > > > > [1] This [2] didn't make it into tree thus I'd be reserved with the > > message printed in your patch too. > > [2] https://lore.kernel.org/all/20250310170442.504716-11-mkoutny@suse.com/ > > I see. Understood. > > > Kind regards, > -- > Aaron Tomlin > --