From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-x431.google.com (mail-pf1-x431.google.com [IPv6:2607:f8b0:4864:20::431]) by mail.toke.dk (Postfix) with ESMTPS id 35E249B9512 for ; Thu, 10 Nov 2022 11:47:49 +0100 (CET) Authentication-Results: mail.toke.dk; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20210112 header.b=jqGCrUUe Received: by mail-pf1-x431.google.com with SMTP id i3so1618736pfc.11 for ; Thu, 10 Nov 2022 02:47:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=xZWmNl+s6/+ylHCRYLaklnEjUiNAAHp+iYnGFNfbckI=; b=jqGCrUUeORBVFvIhuhYXguszWe3kzU+uRddjl4wfCsd5FUpX9G3AsfXU8kW3L7niLM Q/H0jOz6lwyvwZ2Xfrb/c4lk8K/cyY7wIQE9HtUxguZUd8g5cveme+DgbYoThaVmKRsA ozuLwBCfYf0q90R/BMt+g/lHDbdmJKLD6Y29Y8YCNUO8QcS5f1oomHaWwfBNMq6oIU0i 2KTzdK9StUoDhDp9XSSvh5YAc8P+C3USV3URKUlDP7bSyWPGsvHZejCmphblhUYmD5nS yPJkxpq54M1yCk+k395mmx9zQLuqT6t8ShFtF2ycBKKB68Pihjgj/oQc4tHMranNROxs mREQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=xZWmNl+s6/+ylHCRYLaklnEjUiNAAHp+iYnGFNfbckI=; b=weBxwshIIZqb6dBLJrw57oQ5CLnlZyZ9BGoUGf/ylMk3Ecs2r6XMRGtI4Z4Iz4tUc5 fGx0SeH3kzd64nbS6l17EIZ6Uo1Ht/k9L4sNKp2fkc5caT/eoua8t389mpJbvSGFLFLz GE68pYWxRISKycIJBWYL0L6qFlFnr9s9SGk1zKhCCD/7iSgKK4zAmGh4HLvYg5V+IJAg lAFrXCYQA7pubNHPyMr/oc4xLVq8PIhkTYKCU9DRRNDf3Zw1zti/46CVZqOlhdnYcXtW Zc5miniEB8wSATD+bO1uHI4da1q+j0fblyOz8Uk5gC7SG8yTZ2uNP5kM7hbG7/amYlBj JidA== X-Gm-Message-State: ACrzQf01ibjnN7+G6jEh4bLZi3NNGqNVT73MYJziZj/he/Epfo2BSoBp BIL8YkxLy+Uc4FEEB8x8QQe/oG6gM+pmOzNa83NHCWHYfkIGyBVr X-Google-Smtp-Source: AMsMyM5B7R9Y20dOwR14OA9MjHTec76QNVAumQfhA5+n1UZkrhpfHgz4ZoJdt+WYkbHF88uHjHXDl8kt0ZRQm4DVbxM= X-Received: by 2002:a6b:580e:0:b0:6c0:db74:7be1 with SMTP id m14-20020a6b580e000000b006c0db747be1mr2414409iob.92.1668062665318; Wed, 09 Nov 2022 22:44:25 -0800 (PST) MIME-Version: 1.0 References: <20221104032532.1615099-1-sdf@google.com> <20221104032532.1615099-5-sdf@google.com> <636c4514917fa_13c168208d0@john.notmuch> <636c555942433_13ef3820861@john.notmuch> In-Reply-To: <636c555942433_13ef3820861@john.notmuch> From: Stanislav Fomichev Date: Wed, 9 Nov 2022 22:44:14 -0800 Message-ID: To: John Fastabend Content-Type: text/plain; charset="UTF-8" Message-ID-Hash: 3JKVXUG4O6ZW3DBJGBMA22OBYMQVBNJ5 X-Message-ID-Hash: 3JKVXUG4O6ZW3DBJGBMA22OBYMQVBNJ5 X-MailFrom: sdf@google.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, kpsingh@kernel.org, haoluo@google.com, jolsa@kernel.org, David Ahern , Jakub Kicinski , Willem de Bruijn , Jesper Dangaard Brouer , Anatoly Burakov , Alexander Lobakin , Magnus Karlsson , Maryam Tahhan , xdp-hints@xdp-project.net, netdev@vger.kernel.org X-Mailman-Version: 3.3.6 Precedence: list Subject: [xdp-hints] Re: [RFC bpf-next v2 04/14] veth: Support rx timestamp metadata for xdp List-Id: XDP hardware hints design discussion Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Wed, Nov 9, 2022 at 5:35 PM John Fastabend wrote: > > Stanislav Fomichev wrote: > > On Wed, Nov 9, 2022 at 4:26 PM John Fastabend wrote: > > > > > > Stanislav Fomichev wrote: > > > > xskxceiver conveniently setups up veth pairs so it seems logical > > > > to use veth as an example for some of the metadata handling. > > > > > > > > We timestamp skb right when we "receive" it, store its > > > > pointer in new veth_xdp_buff wrapper and generate BPF bytecode to > > > > reach it from the BPF program. > > > > > > > > This largely follows the idea of "store some queue context in > > > > the xdp_buff/xdp_frame so the metadata can be reached out > > > > from the BPF program". > > > > > > > > > > [...] > > > > > > > orig_data = xdp->data; > > > > orig_data_end = xdp->data_end; > > > > + vxbuf.skb = skb; > > > > > > > > act = bpf_prog_run_xdp(xdp_prog, xdp); > > > > > > > > @@ -942,6 +946,7 @@ static int veth_xdp_rcv(struct veth_rq *rq, int budget, > > > > struct sk_buff *skb = ptr; > > > > > > > > stats->xdp_bytes += skb->len; > > > > + __net_timestamp(skb); > > > > > > Just getting to reviewing in depth a bit more. But we hit veth with lots of > > > packets in some configurations I don't think we want to add a __net_timestamp > > > here when vast majority of use cases will have no need for timestamp on veth > > > device. I didn't do a benchmark but its not free. > > > > > > If there is a real use case for timestamping on veth we could do it through > > > a XDP program directly? Basically fallback for devices without hw timestamps. > > > Anyways I need the helper to support hardware without time stamping. > > > > > > Not sure if this was just part of the RFC to explore BPF programs or not. > > > > Initially I've done it mostly so I can have selftests on top of veth > > driver, but I'd still prefer to keep it to have working tests. > > I can't think of a use for it though so its just extra cycles. There > is a helper to read the ktime. As I mentioned in another reply, I wanted something SW-only to test this whole metadata story. The idea was: - veth rx sets skb->tstamp (otherwise it's 0 at this point) - veth kfunc to access rx_timestamp returns skb->tstamp - xsk bpf program verifies that the metadata is non-zero - the above shows end-to-end functionality with a software driver > > Any way I can make it configurable? Is there some ethtool "enable tx > > timestamping" option I can reuse? > > There is a -T option for timestamping in ethtool. There are also the > socket controls for it. So you could spin up a socket and use it. > But that is a bit broken as well I think it would be better if the > timestamp came from the receiving physical nic? > > I have some mlx nics here and a k8s cluster with lots of veth > devices so I could think a bit more. I'm just not sure why I would > want the veth to timestamp things off hand? -T is for dumping only it seems? I'm probably using skb->tstamp in an unconventional manner here :-/ Do you know if enabling timestamping on the socket, as you suggest, will get me some non-zero skb_hwtstamps with xsk? I need something to show how the kfunc can return this data and how can this data land in xdp prog / af_xdp chunk.. > > > > > > skb = veth_xdp_rcv_skb(rq, skb, bq, stats); > > > > if (skb) { > > > > if (skb_shared(skb) || skb_unclone(skb, GFP_ATOMIC)) > >