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 A88B224886A; Sun, 10 May 2026 15:56:03 +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=1778428563; cv=none; b=mE2H/aDgerJw/46cuCclykpwH7BYNCSHE8tc8lT8VKuNj9DqnOlewI0gAwnd4uL+laMCtgJNiAiLoXFsXuaTXNHKwZxU4Gu7iBrU20t7kRS905Fpl6UFIa6eu72rGo83D5FpIDI7PuqboAyd/j2v4KfWmkcis7DJfwxzYH5crDI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778428563; c=relaxed/simple; bh=DKRMHWxdi6z+PAalXzDlkXlxQgstpqQcwYevUkauWbc=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=VkTu1LeU8cpIPOTEgdTljrwIdyfDdLOeHN7VANXS9pY+8D5t6t0cRiSuPUHhfl7PhVliHX+VrlLd69oxCAjs0sEMBnASU8Y97q+GSK9PXMHsulM1ObzXEm/1OVlWr8lPzIyQFBsOl2XbTc09vwQqkUCSWyYtTGo4Tpd2SyvqH9Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RQV28pKR; 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="RQV28pKR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D39C4C2BCB8; Sun, 10 May 2026 15:56:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778428563; bh=DKRMHWxdi6z+PAalXzDlkXlxQgstpqQcwYevUkauWbc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=RQV28pKRGyDtX8i8VLG4sjdOuBLsPPcrUVVYrl352AtpEoubl4CNANLQx/Wf9Wzq6 lCFz97ts4Y5vV/K87QW49Aoecb+DxmBhb63CJgaRz+xlP5wTnrzTPZwhSlbNJ9LnRi fG7zQOexvq40qsX8RaPbA0cHIHph+4+SGXNG57ogcAP2ISHTSYvDuys11ngPjAmivE 2CB4w3VqCGvQw8xJUIjBIWPsmrU8GETuJOpKlaz7qD5+tEU5yAwpL8EQN2NhrIqSoo 4n5qVQowTdegnsvN90dbX2DpQFhWmAUbOzGZ2G7zXfP8eo04wo6ri57JwpfYkxBQcR cZaamJMnxrLzQ== Date: Sun, 10 May 2026 08:56:02 -0700 From: Jakub Kicinski To: Jesper Dangaard Brouer Cc: Simon Schippers , Paolo Abeni , netdev@vger.kernel.org, kernel-team@cloudflare.com, Andrew Lunn , "David S. Miller" , Eric Dumazet , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Stanislav Fomichev , linux-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH net-next v5 3/5] veth: implement Byte Queue Limits (BQL) for latency reduction Message-ID: <20260510085602.57c7a081@kernel.org> In-Reply-To: References: <20260505132159.241305-1-hawk@kernel.org> <20260505132159.241305-4-hawk@kernel.org> <8f2f7f2e-6aa2-4e5b-b52d-0025b2525579@redhat.com> <6a597dbd-70bf-4b14-b495-2f7248fd3220@kernel.org> <20260508190626.4285fac0@kernel.org> 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=US-ASCII Content-Transfer-Encoding: 7bit On Sat, 9 May 2026 11:09:51 +0200 Jesper Dangaard Brouer wrote: > On 09/05/2026 04.06, Jakub Kicinski wrote: > > On Thu, 7 May 2026 21:09:09 +0200 Jesper Dangaard Brouer wrote: > >> Not against being able to modify VETH_RING_SIZE, but I don't think it is > >> the solution here. > > > > Was it evaluated, tho? > > > > It's obviously super easy these days have AI spew no end of complex > > code. So it'd be great to have some solid, ideally production-like > > data to back this all up. > > > > VETH_RING_SIZE seems trivial, ethtool set ringparam > > No, unfortunately we cannot just decrease the VETH_RING_SIZE. To be clear - I said may it configurable with ethtool -G not change the default. > The reason is that XDP-redirect into veth don't have any > back-pressure and would simply drop packets if queue size becomes > less than the NAPI budget (64). (Yes, we use both normal path and > XDP-redirect in production). Doesn't this mean you have a queue which is not under BQL control? > My benchmarking shows that an optimal BQL limit is dynamically > adjusted between 17-55 depending on veth consumer namespace > overhead/speed, when balancing throughput and latency. Testing with prod-approximating traffic pattern and load would be great.