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Thu, 07 May 2026 07:34:09 -0700 (PDT) Received: from [192.168.88.32] ([150.228.93.82]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a886d248a5sm1671466e87.56.2026.05.07.07.34.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 May 2026 07:34:08 -0700 (PDT) Message-ID: <8f2f7f2e-6aa2-4e5b-b52d-0025b2525579@redhat.com> Date: Thu, 7 May 2026 16:34:06 +0200 Precedence: bulk X-Mailing-List: linux-kernel@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: Simon Schippers , hawk@kernel.org, netdev@vger.kernel.org Cc: kernel-team@cloudflare.com, Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , 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> Content-Language: en-US From: Paolo Abeni In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 5/7/26 8:54 AM, Simon Schippers wrote: > On 5/5/26 15:21, hawk@kernel.org wrote: >> @@ -928,9 +968,13 @@ static int veth_xdp_rcv(struct veth_rq *rq, int budget, >> } >> } else { >> /* ndo_start_xmit */ >> - struct sk_buff *skb = ptr; >> + bool bql_charged = veth_ptr_is_bql(ptr); >> + struct sk_buff *skb = veth_ptr_to_skb(ptr); >> >> stats->xdp_bytes += skb->len; >> + if (peer_txq && bql_charged) >> + netdev_tx_completed_queue(peer_txq, 1, VETH_BQL_UNIT); > > In the discussion with Jonas [1], I left a comment explaining why I think > this doesn’t work. > > I still think first that adding an option to modify the hard-coded > VETH_RING_SIZE is the way to go. > > Thanks! > > [1] Link: https://lore.kernel.org/netdev/e8cdba04-aa9a-45c6-9807-8274b62920df@tu-dortmund.de/ In the above discussion a 20% regression is reported, which IMHO can't be ignored. Still the tput figures in the data are extremely low, something is possibly off?!? I would expect a few Mpps with pktgen on top of veth, while the reported data is ~20-30Kpps. /P