From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from imap4.hz.codethink.co.uk (imap4.hz.codethink.co.uk [188.40.203.114]) (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 749262EA16D for ; Fri, 12 Sep 2025 10:34:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=188.40.203.114 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757673251; cv=none; b=Z6VM6SxRxEl+kzop3XTas1/0f0HaBuGye8o8Crz+D3QQH6+6aVzr42fXjIANgCN6HT7yPFyihsmYfIHzYiTClcJZlr09qRahmBp6JyBOu1FEn4+VCxnvSx4wA8KltVoCExjsX2Nz+4HkMgHZaIo56IV/uWuQglMKyrjqA5Gdnn0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757673251; c=relaxed/simple; bh=jGl+MwMWo6epdHwM6byoy8LaqN1pHTitv90iBg1FLhA=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=QJfb74nVRZL3HRXf6aejS03OCZqY+Pqcyyb05slTbgJip+xOwTD7LGj2ZizvI8ZJ19mc3oXGBLImqJ/T1rRYOxmoEsbJOvNbGhjrNKXiFKNfYzD7MwiuLufr7piDtuNQiHMJpUxHhH4B4GGjw0D5WsV88lROJ+D79S2sd4M4h7g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=codethink.co.uk; spf=pass smtp.mailfrom=codethink.co.uk; dkim=pass (2048-bit key) header.d=codethink.co.uk header.i=@codethink.co.uk header.b=XYJFFpkm; arc=none smtp.client-ip=188.40.203.114 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=codethink.co.uk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=codethink.co.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=codethink.co.uk header.i=@codethink.co.uk header.b="XYJFFpkm" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=codethink.co.uk; s=imap4-20230908; h=Sender:MIME-Version: Content-Transfer-Encoding:Content-Type:References:In-Reply-To:Date:Cc:To:From :Subject:Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ps+y4c3ioLI54Zkh/5XUrApcTYorbBi6MpMIscwzpg4=; b=XYJFFpkmYLPNaXR/oPuba4Wm78 jggwOtG9YrLV73Y0QAnyxCkV0DN6GVOlTt+dtnP3Lb2C6mPQ5xTIGSCb5EuQcpQJI7NkzDTgBkltg l5njs5FaCTuVc3aEW1LEKyrs6yclk1xzsbj2ispTeRG50WRm2MvmS/C7GVvgQFCydbNHWmxyyfqHY cVYXgD3WucFMLLcChrSE/494M0NJbucQQbFq1SDGzavdHDcZoe9uKBuNZfErNHEARKOQbMtkJXjO8 o+dbwzMKAaI4XB9GKLQbhpAkxkcLd05I9ehAmAo+nKMhPx1BadfrfiutrhjbIRQS9Spf0KCdLP1Xs ZX9x529w==; Received: from [139.28.87.209] (helo=[10.122.115.253]) by imap4.hz.codethink.co.uk with esmtpsa (Exim 4.94.2 #2 (Debian)) id 1ux0cS-00CVhM-3B; Fri, 12 Sep 2025 11:03:05 +0100 Message-ID: Subject: Re: SCHED_DEADLINE tasks causing WARNING at kernel/sched/sched.h message From: Marcel Ziswiler To: Juri Lelli Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Vineeth Pillai , Luca Abeni Date: Fri, 12 Sep 2025 12:03:01 +0200 In-Reply-To: References: <7481bbd7c6652a963f132191dc622f1003938706.camel@codethink.co.uk> Organization: Codethink Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (by Flathub.org) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: marcel.ziswiler@codethink.co.uk Hi Juri Thanks for getting back to me and sorry for my late reply. On Thu, 2025-09-04 at 11:22 +0200, Juri Lelli wrote: > Hi Marcel, >=20 > On 02/09/25 18:49, Marcel Ziswiler wrote: > > Hi > >=20 > > On Tue, 2025-09-02 at 16:06 +0200, Marcel Ziswiler wrote: > > > As part of our trustable work [1], we also run a lot of real time sch= eduler (SCHED_DEADLINE) tests on the > > > mainline Linux kernel (v6.16.2 in below reported case). > >=20 > > Looking through more logs from earlier test runs I found similar WARN_O= Ns dating back as early as v6.15.3. > > So > > it does not look like a "new" issue in that sense. > >=20 > > [snip] > >=20 > > Any help is much appreciated. Thanks! >=20 > What's the actual workload composition leading the warning. I noticed > stress-ng in the report. Could you please share more details? Yes, sure. It's actually the exact same workload as related to the regressi= on I reported back in April [1]. We currently use three cores as follows: #### core x |sched_deadline =3D sched_period | sched_runtime | CP max run time 90% of s= ched_runtime | utilisation | reclaim | | -- | -- | -- | -- | -- | | 5 ms | 0.15 ms | 0.135 ms | 3.00% | no | | 10 ms | 1.8 ms | 1.62 ms | 18.00% | no | | 10 ms | 2.1 ms | 1.89 ms | 21.00% | no | | 14 ms | 2.3 ms | 2.07 ms | 16.43% | no | | 50 ms | 8.0 ms | 7.20 ms | 16:00% | no | | 10 ms | 0.5 ms | **1 | 5.00% | no | Total utilisation of core x is 79.43% (less than 100%) **1 - this shall be a rogue process. This process will a) run for the maximum allowed workload value=20 b) do not collect execution data #### core y |sched_deadline =3D sched_period | sched_runtime | CP max run time 90% of s= ched_runtime | utilisation | reclaim | | -- | -- | -- | -- | -- | | 5 ms | 0.5 ms | 0.45 ms | 10.00% | no | | 10 ms | 1.9 ms | 1.71 ms | 19.00% | no | | 12 ms | 1.8 ms | 1.62 ms | 15.00% | no | | 50 ms | 5.5 ms | 4.95 ms | 11.00% | no | | 50 ms | 9.0 ms | 8.10 ms | 18.00% | no | Total utilisation of core y is 73.00% (less than 100%) #### core z The third core is special as it will run 50 jobs with the same configuratio= n as such: |sched_deadline =3D sched_period | sched_runtime | CP max run time 90% of s= ched_runtime | utilisation | | -- | -- | -- | -- | | 50 ms | 0.8 ms | 0.72 ms | 1.60% | jobs 1-50 should run with reclaim OFF Total utilisation of core y is 1.6 * 50 =3D 80.00% (less than 100%) In addition to that main workload we also run further stressors like from t= he stress-ng suite. However, only on the remaining cores and in a controlled nsjail/apparmor sandbox. Please let me know if you need any further details which may help figuring = out what exactly is going on. > Thanks! > Juri Cheers Marcel [1] https://lore.kernel.org/all/f532441d8b3cf35e7058305fd9cd3f2cbd3a9fac.ca= mel@codethink.co.uk