From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D54B435E1DA; Thu, 28 May 2026 23:13:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780010033; cv=none; b=GzL24aTcj8evjS9haquBPZlvTBCfu3DXJB01aU8Ca/6+2Jmp9vTBEyjhWAUxZ2o5if/Oj+zod5HOlHSLVwLuRQGpdvREkKA6d2EJosUxbUAqpNgCnN/+UZdIv1wrMy/imT/7/bul3uTH4SxjnliMUmL60tVYdNeKr9L6/uPKu/0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780010033; c=relaxed/simple; bh=Re0/Oe3pENxMAN6cz4Vx4V/QeB9tAti7HcMC32jm9jQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=caY41lXsSJNQQQaTqEX6kPyyc82vQk0V1VS0JufvgkPfNZKh8QMa6sllBXGvocrMhu2AXOWW5OqIyFu2O9t/c/FtOUR8YpQKsnL+vKUP0G7Z9PjQBtLwJxfy87WYi4PUERnhtFqyZWFn91oHAVh+1MyiduQhUY5MA+a0OG4udG0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ov9fUj7E; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ov9fUj7E" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 751A21F000E9; Thu, 28 May 2026 23:13:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780010032; bh=adYNVaD2vWMbHWehET55y+hJOdSX3cbdW6xQxeNIQHU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Ov9fUj7E34C5abfl/vc/iTyDs0DJZEwHEz5iDVGircOiYoo6zEN4l1jsg615mvVSE k0AcUYxrjLHmLpull9uzSnySdMdsp+xoV6n/FINGBVMb4glnfIiLmxwyb6Hc4ushK9 0/NCuoURT0h2OvX/33hqvY2H9mE9xCkzcvOcOh5ZPHOIvEias6cjsfw3O7naWCCUz8 BXCMUzrWRe7kMtALm4FoMGXjJ6tuu/29df65Fwhuu7nZBci2rA3xqKDLvxdIf4aVmt X5msq2ue/5FMit3575/zsb6O9Bo+xV+hpqGuOekLl9vWAhpcfDw2pCM5TxNnYVu1CB hODcUbtqBI5Uw== Message-ID: <0e676b57-ca1a-4f2b-8166-a085fe69e0f2@kernel.org> Date: Fri, 29 May 2026 09:13:44 +1000 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 0/3] selftests: mptcp: reduce bufferbloat and cleanup Content-Language: fr To: Jakub Kicinski Cc: Mat Martineau , Geliang Tang , "David S. Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Shuah Khan , Florian Westphal , netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260527-net-mptcp-sft-bufferbloat-exit-v1-0-9afc4e742090@kernel.org> <20260528144258.58bbc950@kernel.org> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; keydata= xsFNBFXj+ekBEADxVr99p2guPcqHFeI/JcFxls6KibzyZD5TQTyfuYlzEp7C7A9swoK5iCvf YBNdx5Xl74NLSgx6y/1NiMQGuKeu+2BmtnkiGxBNanfXcnl4L4Lzz+iXBvvbtCbynnnqDDqU c7SPFMpMesgpcu1xFt0F6bcxE+0ojRtSCZ5HDElKlHJNYtD1uwY4UYVGWUGCF/+cY1YLmtfb WdNb/SFo+Mp0HItfBC12qtDIXYvbfNUGVnA5jXeWMEyYhSNktLnpDL2gBUCsdbkov5VjiOX7 CRTkX0UgNWRjyFZwThaZADEvAOo12M5uSBk7h07yJ97gqvBtcx45IsJwfUJE4hy8qZqsA62A nTRflBvp647IXAiCcwWsEgE5AXKwA3aL6dcpVR17JXJ6nwHHnslVi8WesiqzUI9sbO/hXeXw TDSB+YhErbNOxvHqCzZEnGAAFf6ges26fRVyuU119AzO40sjdLV0l6LE7GshddyazWZf0iac nEhX9NKxGnuhMu5SXmo2poIQttJuYAvTVUNwQVEx/0yY5xmiuyqvXa+XT7NKJkOZSiAPlNt6 VffjgOP62S7M9wDShUghN3F7CPOrrRsOHWO/l6I/qJdUMW+MHSFYPfYiFXoLUZyPvNVCYSgs 3oQaFhHapq1f345XBtfG3fOYp1K2wTXd4ThFraTLl8PHxCn4ywARAQABzSRNYXR0aGlldSBC YWVydHMgPG1hdHR0YmVAa2VybmVsLm9yZz7CwZEEEwEIADsCGwMFCwkIBwIGFQoJCAsCBBYC AwECHgECF4AWIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZUDpDAIZAQAKCRD2t4JPQmmgcz33 EACjROM3nj9FGclR5AlyPUbAq/txEX7E0EFQCDtdLPrjBcLAoaYJIQUV8IDCcPjZMJy2ADp7 /zSwYba2rE2C9vRgjXZJNt21mySvKnnkPbNQGkNRl3TZAinO1Ddq3fp2c/GmYaW1NWFSfOmw MvB5CJaN0UK5l0/drnaA6Hxsu62V5UnpvxWgexqDuo0wfpEeP1PEqMNzyiVPvJ8bJxgM8qoC cpXLp1Rq/jq7pbUycY8GeYw2j+FVZJHlhL0w0Zm9CFHThHxRAm1tsIPc+oTorx7haXP+nN0J iqBXVAxLK2KxrHtMygim50xk2QpUotWYfZpRRv8dMygEPIB3f1Vi5JMwP4M47NZNdpqVkHrm jvcNuLfDgf/vqUvuXs2eA2/BkIHcOuAAbsvreX1WX1rTHmx5ud3OhsWQQRVL2rt+0p1DpROI 3Ob8F78W5rKr4HYvjX2Inpy3WahAm7FzUY184OyfPO/2zadKCqg8n01mWA9PXxs84bFEV2mP VzC5j6K8U3RNA6cb9bpE5bzXut6T2gxj6j+7TsgMQFhbyH/tZgpDjWvAiPZHb3sV29t8XaOF BwzqiI2AEkiWMySiHwCCMsIH9WUH7r7vpwROko89Tk+InpEbiphPjd7qAkyJ+tNIEWd1+MlX ZPtOaFLVHhLQ3PLFLkrU3+Yi3tXqpvLE3gO3LM7BTQRV4/npARAA5+u/Sx1n9anIqcgHpA7l 5SUCP1e/qF7n5DK8LiM10gYglgY0XHOBi0S7vHppH8hrtpizx+7t5DBdPJgVtR6SilyK0/mp 9nWHDhc9rwU3KmHYgFFsnX58eEmZxz2qsIY8juFor5r7kpcM5dRR9aB+HjlOOJJgyDxcJTwM 1ey4L/79P72wuXRhMibN14SX6TZzf+/XIOrM6TsULVJEIv1+NdczQbs6pBTpEK/G2apME7vf mjTsZU26Ezn+LDMX16lHTmIJi7Hlh7eifCGGM+g/AlDV6aWKFS+sBbwy+YoS0Zc3Yz8zrdbi Kzn3kbKd+99//mysSVsHaekQYyVvO0KD2KPKBs1S/ImrBb6XecqxGy/y/3HWHdngGEY2v2IP Qox7mAPznyKyXEfG+0rrVseZSEssKmY01IsgwwbmN9ZcqUKYNhjv67WMX7tNwiVbSrGLZoqf Xlgw4aAdnIMQyTW8nE6hH/Iwqay4S2str4HZtWwyWLitk7N+e+vxuK5qto4AxtB7VdimvKUs x6kQO5F3YWcC3vCXCgPwyV8133+fIR2L81R1L1q3swaEuh95vWj6iskxeNWSTyFAVKYYVskG V+OTtB71P1XCnb6AJCW9cKpC25+zxQqD2Zy0dK3u2RuKErajKBa/YWzuSaKAOkneFxG3LJIv Hl7iqPF+JDCjB5sAEQEAAcLBXwQYAQIACQUCVeP56QIbDAAKCRD2t4JPQmmgc5VnD/9YgbCr HR1FbMbm7td54UrYvZV/i7m3dIQNXK2e+Cbv5PXf19ce3XluaE+wA8D+vnIW5mbAAiojt3Mb 6p0WJS3QzbObzHNgAp3zy/L4lXwc6WW5vnpWAzqXFHP8D9PTpqvBALbXqL06smP47JqbyQxj Xf7D2rrPeIqbYmVY9da1KzMOVf3gReazYa89zZSdVkMojfWsbq05zwYU+SCWS3NiyF6QghbW voxbFwX1i/0xRwJiX9NNbRj1huVKQuS4W7rbWA87TrVQPXUAdkyd7FRYICNW+0gddysIwPoa KrLfx3Ba6Rpx0JznbrVOtXlihjl4KV8mtOPjYDY9u+8x412xXnlGl6AC4HLu2F3ECkamY4G6 UxejX+E6vW6Xe4n7H+rEX5UFgPRdYkS1TA/X3nMen9bouxNsvIJv7C6adZmMHqu/2azX7S7I vrxxySzOw9GxjoVTuzWMKWpDGP8n71IFeOot8JuPZtJ8omz+DZel+WCNZMVdVNLPOd5frqOv mpz0VhFAlNTjU1Vy0CnuxX3AM51J8dpdNyG0S8rADh6C8AKCDOfUstpq28/6oTaQv7QZdge0 JY6dglzGKnCi/zsmp2+1w559frz4+IC7j/igvJGX4KDDKUs0mlld8J2u2sBXv7CGxdzQoHaz lzVbFe7fduHbABmYz9cefQpO7wDE/Q== Organization: NGI0 Core In-Reply-To: <20260528144258.58bbc950@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Jakub, On 29/05/2026 07:42, Jakub Kicinski wrote: > On Wed, 27 May 2026 22:11:33 +1000 Matthieu Baerts (NGI0) wrote: >> Bufferbloat is baaaad, even in our selftests: let's kill it (or at least >> reduce it). By doing that, the tests (seem to) have a more stable >> transfer, and are then less unstable. That's what patches 1-2 are doing, >> and they can be backported up to 5.10. > > Could you explain a little more what this is actually fixing? The simult_flows.sh test simulates very low speed links using netem qdiscs. With the current configuration, still a large amount of packets can be queued, which means high TCP RTT samples and then large receive buffer size. Minimal inaccuracy in the pacing rate can lead to using only one subflow towards the end of the connection for a considerable amount of data, while the test expects to use the 2 available paths in parallel. > Does it give a huge increase in test stability? I would say no: the test was not that flaky, mainly on NIPA in fact, and around 4% in the last 100 tests [1]. On my side, I had to get my system busy to reproduce the issues. My hope is that the success rate on NIPA switches from 96 to ~100%. No failure since its introduction in "net-next-2026-05-27--15-00". I sent them to net, just to increase the stability when validating stable kernels as well. But all of this is not urgent, and this series can be applied in net-next if preferred. Do you want me to resend this series targeting net-next? [1] https://netdev.bots.linux.dev/flakes.html?tn-needle=simult-flows-sh Cheers, Matt -- Sponsored by the NGI0 Core fund.