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 8AB99A31 for ; Tue, 7 Jan 2025 03:19:17 +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=1736219957; cv=none; b=gO6JRbpTszw4/Pn8xiE3I0GoG6drnRwGATOcM3AAViRp8Kkz9BhPW079DsBuuqtuWSFHydcwpnpIv/J2vs73YqGIsFOidehurVmBAfHp+T3hrW+5UW89xhK+qhlw8bqnyQ8Isk34goRuHTSX7H/PhB2GUM1PRWz4EmbIegjoe6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736219957; c=relaxed/simple; bh=/6oWaL4VinYN9kupmJYKP8VBA+nGvGQy6rJfUb5M+C4=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=WVXSQQjHgYuL/b0Up2chRC/zsW7iJhK7rAWVonJJrpKxFgDu/6aa1oza7WsCY/AcmNusDtGtZueaHjPFSy1XS0uAJXpQWIiprlgsOusIqwlsR+FgoVPe4qGbneUxIBSX3vTjnvlFAtSo1qYRqjijrVGwlvet/5Z6HA8IkAhLmIg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GnKbN6Xk; 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="GnKbN6Xk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3816C4CEDF; Tue, 7 Jan 2025 03:19:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736219957; bh=/6oWaL4VinYN9kupmJYKP8VBA+nGvGQy6rJfUb5M+C4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=GnKbN6XkFcz1//HbmjItKzV1sqgpkntXSmlmu1RH/YPbrUr/+FQWpkA0ThnqyR12Q fJAGqdw6bas8Ivafqxtk89RPsKnyOdtLBwhNFQRpxkBHdeArYx9YxcjSqLOkVLF6RO eK3hr9ee/weZXgMfgz8jV7dJVmfZF4wOfMkChYMhAdUfQ3Kal4+BGEZjcbTfTUSbdp JngVukb6LlwK89QSA8tlwIoMvHt9XX5lc3/jH3w6VQANK5SpTEiWHoJtlN9m226hsn AS0OYl1+7iCKP0/aRcCj4eavXzxtWp74vqQaBNIQNVNtHZ8Eg7nwW631af4IrhCS9M mQApcmmu4tflg== Date: Mon, 6 Jan 2025 19:19:16 -0800 From: Jakub Kicinski To: Neal Cardwell Cc: Teodor Milkov , netdev@vger.kernel.org, mst@redhat.com, jasowang@redhat.com Subject: Re: Download throttling with kernel 6.6 (in KVM guests) Message-ID: <20250106191916.6e26b3fd@kernel.org> In-Reply-To: References: <20250106132051.262177da@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Mon, 6 Jan 2025 21:50:02 -0500 Neal Cardwell wrote: > On Mon, Jan 6, 2025 at 4:20=E2=80=AFPM Jakub Kicinski w= rote: > > On Mon, 6 Jan 2025 22:15:37 +0200 Teodor Milkov wrote: =20 > > > Hello, > > > > > > Following up on my previous email, I=E2=80=99ve found the issue occurs > > > specifically with the |virtio-net| driver in KVM guests. Switching to > > > the |e1000| driver resolves the slowdown entirely, with no throttling= in > > > subsequent downloads. > > > > > > The reproducer and observations remain the same, but this detail might > > > help narrow down the issue. =20 > > > > Let's CC the virtio maintainers, then. > > > > The fact that a 300ms sleep between connections makes the problem > > go away is a bit odd from the networking perspective. > > > > You may need to find a way to automate the test and try to bisect > > it down :( This may help: https://github.com/arighi/virtme-ng =20 >=20 > IIUC, from Teodor's earlier message in the thread it sounds like he > was able to bisect the issue; he mentioned that git bisect traced the > regression to the commit: >=20 > dfa2f0483360 ("tcp: get rid of sysctl_tcp_adv_win_scale") My bad. I think I looked at it last week and couldn't figure out=20 why the sleep make any difference.