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 6BF3E396590; Sat, 9 May 2026 09:09:57 +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=1778317797; cv=none; b=PrIBAhIkan6Aspk5PghHu0eYoG2qSvYPAPKP6JJ+Iymh3TVKBxiNuqGwC4Y7aB3mePPzHP9Iz2ttcg7BUPNGKw10yj8SsDNSgFr8ZiyjUCc/KsHF3SEtXmwfxz4h8rpHz67gQG1P567aC+N56Hs7g8RDVNkrCi8mm1Kx/v+HoyM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778317797; c=relaxed/simple; bh=I9xmCKGHzYxSSinS9IY36jR9jBt7BmV4S2kZeKuaUp4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uSKteQMDLX3FLUHnoV0e6EoLMZHnzFQv0RKVSyN0i0t/g6DV6176zSjkw0oVjznajpvVQFWS4Bq9DUIr4MSKR4QpTIv+M5j4PHcFhZFC1guNODoQ2WAalzLDBddH1BOx3NihCvbnMvdybEA+VZoSNm9VX0W2DrJ3JRL5wB+Xprw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bc4YlmP/; 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="bc4YlmP/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4F360C2BCB2; Sat, 9 May 2026 09:09:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778317796; bh=I9xmCKGHzYxSSinS9IY36jR9jBt7BmV4S2kZeKuaUp4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=bc4YlmP/sUpsEYe9VaGxXj/JScjxIU7hY0Wddht5Pg+tOeTnpG2tGATpEs0M9yEa+ eyTFeaTdXirU9ts2g9Vmqfc/np6rgLyUWVH/YE1ru+g0hRibmzs1t0vBTigHyUxN9n I8NtAtvB9iZhFn/ZoLCqheoEcAVPh6DGPPx9EkAZnuLyCSkgmPjFM/FRWFHfwKLMWw xMkxrNZpmXidWaFfkFChQhnAn25o17jJk8RFDQDD7A0rnm+PjDPAuwKVTVfw5c4vdD FFSZaL934Stwmlhq7vc6z0+xrzMBYaRuvFnlmefKIUju4po6E7arf4N3BCDBY4JpBV e9MmHdtGZmIzg== Message-ID: Date: Sat, 9 May 2026 11:09:51 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v5 3/5] veth: implement Byte Queue Limits (BQL) for latency reduction To: Jakub Kicinski 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 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> Content-Language: en-US From: Jesper Dangaard Brouer In-Reply-To: <20260508190626.4285fac0@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 09/05/2026 04.06, Jakub Kicinski wrote: > On Thu, 7 May 2026 21:09:09 +0200 Jesper Dangaard Brouer wrote: >>>>> I still think first that adding an option to modify the hard-coded >>>>> VETH_RING_SIZE is the way to go. >> >> 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. 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). 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. --Jesper