From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D05CC433B4 for ; Wed, 21 Apr 2021 15:39:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F24266144C for ; Wed, 21 Apr 2021 15:39:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243581AbhDUPkO (ORCPT ); Wed, 21 Apr 2021 11:40:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:37293 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238880AbhDUPkN (ORCPT ); Wed, 21 Apr 2021 11:40:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619019580; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bVNum44dAUpgnvC+nvXv78yCMxeDErB6G4dWdidL3ZY=; b=WAlgfhwXKvJnl8OM5/VaLTFjVQydnXsTRsB/NjTN8+qFXxs7pT1UPUG1MIxSwdfpYVlaWb XPTIAoOKXY9cHZWpitGo8N5PuulHARjhE0FFi+ycKvNM72rlPOwnbF7z5+ZYvCUnDBY5Ml WLOIYAwbDWozQOb7t2pcOS5P2aiZONY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-518-0DfOuL98OdOOIP3D4PeMdA-1; Wed, 21 Apr 2021 11:39:37 -0400 X-MC-Unique: 0DfOuL98OdOOIP3D4PeMdA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AC88B1008064; Wed, 21 Apr 2021 15:39:34 +0000 (UTC) Received: from carbon (unknown [10.36.110.19]) by smtp.corp.redhat.com (Postfix) with ESMTP id F306B19726; Wed, 21 Apr 2021 15:39:22 +0000 (UTC) Date: Wed, 21 Apr 2021 17:39:21 +0200 From: Jesper Dangaard Brouer To: Magnus Karlsson Cc: Lorenzo Bianconi , Lorenzo Bianconi , bpf , Network Development , "David S. Miller" , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , shayagr@amazon.com, sameehj@amazon.com, John Fastabend , David Ahern , Eelco Chaudron , Jason Wang , Alexander Duyck , Saeed Mahameed , "Fijalkowski, Maciej" , Tirthendu , brouer@redhat.com Subject: Re: [PATCH v8 bpf-next 00/14] mvneta: introduce XDP multi-buffer support Message-ID: <20210421173921.23fef6a7@carbon> In-Reply-To: References: <20210418181801.17166935@carbon> <20210421144747.33c5f51f@carbon> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, 21 Apr 2021 16:12:32 +0200 Magnus Karlsson wrote: > On Wed, Apr 21, 2021 at 2:48 PM Jesper Dangaard Brouer > wrote: > > > > On Tue, 20 Apr 2021 15:49:44 +0200 > > Magnus Karlsson wrote: > > > > > On Mon, Apr 19, 2021 at 8:56 AM Lorenzo Bianconi > > > wrote: > > > > > > > > > On Sun, Apr 18, 2021 at 6:18 PM Jesper Dangaard Brouer > > > > > wrote: > > > > > > > > > > > > On Fri, 16 Apr 2021 16:27:18 +0200 > > > > > > Magnus Karlsson wrote: > > > > > > > > > > > > > On Thu, Apr 8, 2021 at 2:51 PM Lorenzo Bianconi wrote: > > > > > > > > > > > > > > > > This series introduce XDP multi-buffer support. The mvneta driver is > > > > > > > > the first to support these new "non-linear" xdp_{buff,frame}. Reviewers > > > > > > > > please focus on how these new types of xdp_{buff,frame} packets > > > > > > > > traverse the different layers and the layout design. It is on purpose > > > > > > > > that BPF-helpers are kept simple, as we don't want to expose the > > > > > > > > internal layout to allow later changes. > > > > > > > > > > > > > > > > For now, to keep the design simple and to maintain performance, the XDP > > > > > > > > BPF-prog (still) only have access to the first-buffer. It is left for > > > > > > > > later (another patchset) to add payload access across multiple buffers. > > > > > > > > This patchset should still allow for these future extensions. The goal > > > > > > > > is to lift the XDP MTU restriction that comes with XDP, but maintain > > > > > > > > same performance as before. > > > > > > [...] > > > > > > > > > > > > > > > > [0] https://netdevconf.info/0x14/session.html?talk-the-path-to-tcp-4k-mtu-and-rx-zerocopy > > > > > > > > [1] https://github.com/xdp-project/xdp-project/blob/master/areas/core/xdp-multi-buffer01-design.org > > > > > > > > [2] https://netdevconf.info/0x14/session.html?tutorial-add-XDP-support-to-a-NIC-driver (XDPmulti-buffers section) > > > > > > > > > > > > > > Took your patches for a test run with the AF_XDP sample xdpsock on an > > > > > > > i40e card and the throughput degradation is between 2 to 6% depending > > > > > > > on the setup and microbenchmark within xdpsock that is executed. And > > > > > > > this is without sending any multi frame packets. Just single frame > > > > > > > ones. Tirtha made changes to the i40e driver to support this new > > > > > > > interface so that is being included in the measurements. > > > > > > > > > > > > Could you please share Tirtha's i40e support patch with me? > > > > > > > > > > We will post them on the list as an RFC. Tirtha also added AF_XDP > > > > > multi-frame support on top of Lorenzo's patches so we will send that > > > > > one out as well. Will also rerun my experiments, properly document > > > > > them and send out just to be sure that I did not make any mistake. > > > > > > > > ack, very cool, thx > > > > > > I have now run a new set of experiments on a Cascade Lake server at > > > 2.1 GHz with turbo boost disabled. Two NICs: i40e and ice. The > > > baseline is commit 5c507329000e ("libbpf: Clarify flags in ringbuf > > > helpers") and Lorenzo's and Eelco's path set is their v8. First some > > > runs with xdpsock (i.e. AF_XDP) in both 2-core mode (app on one core > > > and the driver on another) and 1-core mode using busy_poll. > > > > > > xdpsock rxdrop throughput change with the multi-buffer patches without > > > any driver changes: > > > 1-core i40e: -0.5 to 0% 2-cores i40e: -0.5% > > > 1-core ice: -2% 2-cores ice: -1 to -0.5% > > > > > > xdp_rxq_info -a XDP_DROP > > > i40e: -4% ice: +8% > > > > > > xdp_rxq_info -a XDP_TX > > > i40e: -10% ice: +9% > > > > > > The XDP results with xdp_rxq_info are just weird! I reran them three > > > times, rebuilt and rebooted in between and I always get the same > > > results. And I also checked that I am running on the correct NUMA node > > > and so on. But I have a hard time believing them. Nearly +10% and -10% > > > difference. Too much in my book. Jesper, could you please run the same > > > and see what you get? > > > > We of-cause have to find the root-cause of the +-10%, but let me drill > > into what the 10% represent time/cycle wise. Using a percentage > > difference is usually a really good idea as it implies a comparative > > measure (something I always request people to do, as a single > > performance number means nothing by itself). > > > > For a zoom-in-benchmarks like these where the amount of code executed > > is very small, the effect of removing or adding code can effect the > > measurement a lot. > > > > I can only do the tests for i40e, as I don't have ice hardware (but > > Intel is working on fixing that ;-)). > > > > xdp_rxq_info -a XDP_DROP > > i40e: 33,417,775 pps > > Here I only get around 21 Mpps > > > CPU is 100% used, so we can calculate nanosec used per packet: > > 29.92 nanosec (1/33417775*10^9) > > 2.1 GHz CPU = approx 63 CPU-cycles > > > > You lost -4% performance in this case. This correspond to: > > -1.2 nanosec (29.92*0.04) slower > > (This could be cost of single func call overhead = 1.3 ns) > > > > My measurement for XDP_TX: > > > > xdp_rxq_info -a XDP_TX > > 28,278,722 pps > > 35.36 ns (1/28278722*10^9) > > And here, much lower at around 8 Mpps. But I do see correct packets > coming back on the cable for i40e but not for ice! There is likely a > bug there in the XDP_TX logic for ice. Might explain the weird results > I am getting. Will investigate. > > But why do I get only a fraction of your performance? XDP_TX touches > the packet so I would expect it to be far less than what you get, but > more than I get. I clearly have a bug in the i40e driver. As I wrote later, I don't see any packets transmitted for XDP_TX. Hmm, I using Mel Gorman's tree, which doesn't contain the i40e/ice/ixgbe bug we fixed earlier. The call to xdp_convert_buff_to_frame() fails, but (see below) that error is simply converted to I40E_XDP_CONSUMED. Thus, not even the 'trace_xdp_exception' will be able to troubleshoot this. You/Intel should consider making XDP_TX errors detectable (this will also happen if TX ring don't have room). int i40e_xmit_xdp_tx_ring(struct xdp_buff *xdp, struct i40e_ring *xdp_ring) { struct xdp_frame *xdpf = xdp_convert_buff_to_frame(xdp); if (unlikely(!xdpf)) return I40E_XDP_CONSUMED; return i40e_xmit_xdp_ring(xdpf, xdp_ring); } > What CPU core do you run on? Intel(R) Xeon(R) CPU E5-1650 v4 @ 3.60GHz > It actually looks like > your packet data gets prefetched successfully. If it had not, you > would have gotten an access to LLC which is much more expensive than > the drop you are seeing. If I run on the wrong NUMA node, I get 4 > Mpps, so it is not that. > > One interesting thing is that I get better results using the zero-copy > path in the driver. I start xdp_rxq_drop then tie an AF_XDP socket to > the queue id the XDP program gets its traffic from. The AF_XDP program > will get no traffic in this case, but it will force the driver to use > the zero-copy path for its XDP processing. In this case I get this: > > -0.5% for XDP_DROP and +-0% for XDP_TX for i40e. > > > You lost -10% performance in this case: > > -3.54 nanosec (35.36*0.10) slower > > > > In XDP context 3.54 nanosec is a lot, as you can see it is 10% in this > > zoom-in benchmark. We have to look at the details. > > > > One detail/issue with i40e doing XDP_TX, is that I cannot verify that > > packets are actually transmitted... not via exception tracepoint, not > > via netstats, not via ethtool_stats.pl. Maybe all the packets are > > getting (silently) drop in my tests...!?! > > > > > > > The xdpsock numbers are more in the ballpark of > > > what I would expect. > > > > > > Tirtha and I found some optimizations in the i40e > > > multi-frame/multi-buffer support that we have implemented. Will test > > > those next, post the results and share the code. > > > > > > > > > > > > > Just note that I would really like for the multi-frame support to get > > > > > in. I have lost count on how many people that have asked for it to be > > > > > added to XDP and AF_XDP. So please check our implementation and > > > > > improve it so we can get the overhead down to where we want it to be. > > > > > > > > sure, I will do. > > > > > > > > Regards, > > > > Lorenzo > > > > > > > > > > > > > > Thanks: Magnus > > > > > > > > > > > I would like to reproduce these results in my testlab, in-order to > > > > > > figure out where the throughput degradation comes from. > > > > > > > > > > > > > What performance do you see with the mvneta card? How much are we > > > > > > > willing to pay for this feature when it is not being used or can we in > > > > > > > some way selectively turn it on only when needed? > > > > > > > > > > > > Well, as Daniel says performance wise we require close to /zero/ > > > > > > additional overhead, especially as you state this happens when sending > > > > > > a single frame, which is a base case that we must not slowdown. > > > > > > > > > > > > -- > > > > > > Best regards, > > > > > > Jesper Dangaard Brouer > > > > -- > > Best regards, > > Jesper Dangaard Brouer > > MSc.CS, Principal Kernel Engineer at Red Hat > > LinkedIn: http://www.linkedin.com/in/brouer > > > > > > Running XDP on dev:i40e2 (ifindex:6) action:XDP_DROP options:read > > XDP stats CPU pps issue-pps > > XDP-RX CPU 2 33,417,775 0 > > XDP-RX CPU total 33,417,775 > > > > RXQ stats RXQ:CPU pps issue-pps > > rx_queue_index 2:2 33,417,775 0 > > rx_queue_index 2:sum 33,417,775 > > > > > > Running XDP on dev:i40e2 (ifindex:6) action:XDP_TX options:swapmac > > XDP stats CPU pps issue-pps > > XDP-RX CPU 2 28,278,722 0 > > XDP-RX CPU total 28,278,722 > > > > RXQ stats RXQ:CPU pps issue-pps > > rx_queue_index 2:2 28,278,726 0 > > rx_queue_index 2:sum 28,278,726 > > > > > > > -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer