From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DB16C1DE2DE; Mon, 4 Aug 2025 09:59:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754301542; cv=none; b=gRv/KlqZpsr7J4Y+XbK/FbdhGM3rNI86MrcZBIwPGaflBZ/PfEjxdOortv8AH6TxOCH/SZw27oOlCmFAzLB6QM4A3P9gFVKIO3OTzBwPCaC5eJZHflP67GtIc1D3VoSiBZlFOAMnVT8RRFAMO6zcMgvy/+3LbeptsgulRt0cNUI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754301542; c=relaxed/simple; bh=PfXG0y/uT6Sh3+8w9sEkgBSv0GsvkI9O3hS4R2wxk5c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mZWtnGlxlHgv7GPZlsp4g5gRVDQ0Zq9sGvV9m9dvO0GJHx/mwXtukzs9VAYdHnQnb1EdDd4/bFPyB3v2idp9cHSCVyRMcgekQMURZ5nW5SRhatVc8L87JD+lvviF0puWifWLP1tZoRMiZxCHZelEkAyVjR3XJ+a7WWE+1C91F9g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=s6SrOArQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="s6SrOArQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 89FEBC4CEE7; Mon, 4 Aug 2025 09:58:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754301541; bh=PfXG0y/uT6Sh3+8w9sEkgBSv0GsvkI9O3hS4R2wxk5c=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=s6SrOArQ0CHnr6400POZE1gBYZasggm0ND1DooTqCNLVBptAixZYR0OvwoDc2f2GX 1kAZOip4FQj7Qw3UwtihwAbTeIkx+SPKSsNOU/POTWUepXrErmXlTWBZiINznFOqfM j2JlXzPWEtjCJ6iP0Pkw1144/3lb7Q8ky1WU8dh1TvKaangib30XIykl5kA2S0A7HC F9aMxWck1Q+ytjovgVjnAr/EdbofLjOUSvf0tyqsD5TWAT7Fa3kkVuXPK074z6YGxL UmCoAdx/JoyLQ6tPedqoQuE7Qptc0QsT8qKZ6XNA+EjewErauMrOAs+MB8vNy6uFr3 BvUMt/VcwYFjA== Message-ID: <88a51699-e913-4dba-992d-e923509ec754@kernel.org> Date: Mon, 4 Aug 2025 11:58:54 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH net] selftests: net: packetdrill: xfail all problems on slow machines Content-Language: en-GB, fr-BE To: Jakub Kicinski , willemb@google.com Cc: netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, shuah@kernel.org, linux-kselftest@vger.kernel.org, davem@davemloft.net References: <20250801181638.2483531-1-kuba@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Jakub, Willem, On 01/08/2025 20:16, Jakub Kicinski wrote: > We keep seeing flakes on packetdrill on debug kernels, while > non-debug kernels are stable, not a single flake in 200 runs. > Time to give up, debug kernels appear to suffer from 10msec > latency spikes and any timing-sensitive test is bound to flake. Thank you for the patch! Another solution might be to increase the tolerance, but I don't think it will fix all issues. I quickly looked at the last 100 runs, and I think most failures might be fixed by a higher tolerance, e.g. > # tcp_ooo-before-and-after-accept.pkt:19: timing error: expected inbound packet at 0.101619 sec but happened at 0.115894 sec; tolerance 0.014000 sec (0.275ms above the limit!) On MPTCP, we used to have a very high tolerance with debug kernels (>0.5s) when public CIs were very limited in terms of CPU resources. I guess having a tolerance of 0.1s would be enough, but for these MPTCP packetdrill tests, I put 0.2s for the tolerance with a debug kernel, just to be on the safe side. Still, I think increasing the tolerance would not fix all issues. On MPTCP side, the latency introduced by debug kernel caused unexpected retransmissions due to too low RTO. I took the time to make sure injected packets were always done with enough delay, but with the TCP packetdrill tests here, it is possibly not enough to do that when I look at some recent errors, e.g. > tcp_zerocopy_batch.pkt:26: error handling packet: live packet payload: expected 4000 bytes vs actual 5000 bytes At the end, and as previously mentioned, these adaptations for debug kernel are perhaps not worth it: in this environment, it is probably enough to ignore packetdrill results and focus on kernel warnings. Acked-by: Matthieu Baerts (NGI0) Cheers, Matt -- Sponsored by the NGI0 Core fund.