From owner-freebsd-net@FreeBSD.ORG Wed Sep 17 17:27:54 2014 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 4BEF81AE; Wed, 17 Sep 2014 17:27:54 +0000 (UTC) Received: from mail-we0-x230.google.com (mail-we0-x230.google.com [IPv6:2a00:1450:400c:c03::230]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id A63FCC5E; Wed, 17 Sep 2014 17:27:53 +0000 (UTC) Received: by mail-we0-f176.google.com with SMTP id q58so1808179wes.7 for ; Wed, 17 Sep 2014 10:27:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type:content-transfer-encoding; bh=CqkJj04bKoVkqwNWE/3LPFsCq/iSjXSMkcLUraTOhlY=; b=uK154Uu4VorKdEC2Ewh4+/e97L0+yq3wJFnmXpoEltE6aI/VDQUKCmJajAy7hADKZn EtvxT05XNMMrszslqYZzlpvMWxv7HGWPvRSwNgN3sZaLXYL81o0wsueUxyqcGd+EyUXk owjGsXdNDpeswTR4oshyhwpwZMKoMQDRUXN73POKvbLhFkP4APQ8JiWHGn8xpICBtIRD 05a8SIrBPUMgxFdD0lvackzyxT+HVezXx9s5BeDMx4+BzpGC+j1GLKKhJw0lTnDBa7xK ozMDfBYIylNnA1EiBKAGYGnXxdEnX8aA4TuN0pBvDhD4Kv2oOwD/ZEYGVE5OqYWWDgS3 QGdw== MIME-Version: 1.0 X-Received: by 10.180.107.100 with SMTP id hb4mr6868225wib.59.1410974871879; Wed, 17 Sep 2014 10:27:51 -0700 (PDT) Sender: adrian.chadd@gmail.com Received: by 10.216.106.199 with HTTP; Wed, 17 Sep 2014 10:27:51 -0700 (PDT) In-Reply-To: References: Date: Wed, 17 Sep 2014 10:27:51 -0700 X-Google-Sender-Auth: FjTR5MgoHUE-TJW01cfMvbtYY3Y Message-ID: Subject: Re: [RFC] Patch to add Software/Generic Segmentation Offload (GSO) support in FreeBSD From: Adrian Chadd To: Stefano Garzarella Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: "freebsd-net@freebsd.org" , freebsd-current , Luigi Rizzo X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 17 Sep 2014 17:27:54 -0000 Hi! Cool! How many flows were you testing with? Just one or two? It's for outbound, so it's not _as_ big a deal as it is for inbound, but it'd still be nice to know. -a On 17 September 2014 01:27, Stefano Garzarella wrote: > Hi all, > I have recently worked, during my master=E2=80=99s thesis with the superv= ision > of Prof. Luigi Rizzo, on a project to add GSO (Generic Segmentation > Offload) support in FreeBSD. I will present this project at EuroBSDcon > 2014, in Sofia (Bulgaria) on September 28, 2014. > > Following is a brief description of our project: > > The use of large frames makes network communication much less > demanding for the CPU. Yet, backward compatibility and slow links > requires the use of 1500 byte or smaller frames. Modern NICs with > hardware TCP segmentation offloading (TSO) address this problem. > However, a generic software version (GSO) provided by the OS has > reason to exist, for use on paths with no suitable hardware, such > as between virtual machines or with older or buggy NICs. > > Much of the advantage of TSO comes from crossing the network stack only > once per (large) segment instead of once per 1500-byte frame. > GSO does the same both for segmentation (TCP) and fragmentation (UDP) > by doing these operations as late as possible. Ideally, this could be don= e > within the device driver, but that would require modifications to all > drivers. > A more convenient, similarly effective approach is to segment > just before the packet is passed to the driver (in ether_output()). > > Our preliminary implementation supports TCP and UDP on IPv4/IPv6; > it only intercepts packets large than the MTU (others are left unchanged)= , > and only when GSO is marked as enabled for the interface. > > Segments larger than the MTU are not split in tcp_output(), > udp_output(), or ip_output(), but marked with a flag (contained in > m_pkthdr.csum_flags), which is processed by ether_output() just > before calling the device driver. > > ether_output(), through gso_dispatch(), splits the large frame as needed, > creating headers and possibly doing checksums if not supported by > the hardware. > > In experiments agains an LRO-enabled receiver (otherwise TSO/GSO > are ineffective) we have seen the following performance, > taken at different clock speeds (because at top speeds the > 10G link becomes the bottleneck): > > > Testing enviroment (all with Intel 10Gbit NIC) > Sender: FreeBSD 11-CURRENT - CPU i7-870 at 2.93 GHz + Turboboost > Receiver: Linux 3.12.8 - CPU i7-3770K at 3.50GHz + Turboboost > Benchmark tool: netperf 2.6.0 > > --- TCP/IPv4 packets (checksum offloading enabled) --- > Freq. TSO GSO none Speedup > [GHz] [Gbps] [Gbps] [Gbps] GSO-none > 2.93 9347 9298 8308 12 % > 2.53 9266 9401 6771 39 % > 2.00 9408 9294 5499 69 % > 1.46 9408 8087 4075 98 % > 1.05 9408 5673 2884 97 % > 0.45 6760 2206 1244 77 % > > > --- TCP/IPv6 packets (checksum offloading enabled) --- > Freq. TSO GSO none Speedup > [GHz] [Gbps] [Gbps] [Gbps] GSO-none > 2.93 7530 6939 4966 40 % > 2.53 5133 7145 4008 78 % > 2.00 5965 6331 3152 101 % > 1.46 5565 5180 2348 121 % > 1.05 8501 3607 1732 108 % > 0.45 3665 1505 651 131 % > > > --- UDP/IPv4 packets (9K) --- > Freq. GSO none Speedup > [GHz] [Gbps] [Gbps] GSO-none > 2.93 9440 8084 17 % > 2.53 7772 6649 17 % > 2.00 6336 5338 19 % > 1.46 4748 4014 18 % > 1.05 3359 2831 19 % > 0.45 1312 1120 17 % > > > --- UDP/IPv6 packets (9K) --- > Freq. GSO none Speedup > [GHz] [Gbps] [Gbps] GSO-none > 2.93 7281 6197 18 % > 2.53 5953 5020 19 % > 2.00 4804 4048 19 % > 1.46 3582 3004 19 % > 1.05 2512 2092 20 % > 0.45 998 826 21 % > > We tried to change as little as possible the network stack to add > GSO support. To avoid changing API/ABI, we temporarily used spare > fields in struct tcpcb (TCP Control Block) and struct ifnet to store > some information related to GSO (enabled, max burst size, etc.). > The code that performs the segmentation/fragmentation is contained > in the file gso.[h|c] in sys/net. We used 4 bit in m_pkthdr.csum_flags > (CSUM_GSO_MASK) to encode the packet type (TCP/IPv4, TCP/IPv6, etc) > to prevent access to the TCP/IP/Ethernet headers of each packet. > In ether_output_frame(), if the packet requires the GSO > ((m->m_pkthdr.csum_flags & CSUM_GSO_MASK) !=3D 0), it is segmented > or fragmented, and then they are sent to the device driver. > > At https://github.com/stefano-garzarella/freebsd-gso > you can find the kernel patches for FreeBSD-current, FreeBSD > 10-stable, FreeBSD 9-stable, a simple application (gso-stats.c) > that prints the GSO statistics and picobsd images with GSO support. > > At https://github.com/stefano-garzarella/freebsd-gso-src > you can get the FreeBSD source with GSO patch (various branch for > FreeBSD current, 10-stable, 9-stable). > > Any feedbacks, comments, questions are welcome. > > Thank you very much, > Stefano Garzarella > > -------------------------------------------------------------------------= ----------------------------------- > How to use GSO: > > - Apply the right kernel patch. > > - To compile the GSO support add =E2=80=98 options GSO ' to your kernel c= onfig file > and > rebuild a kernel. > > - To manage the GSO parameters there are some sysctls: > - net.inet.tcp.gso - GSO enable on TCP communications (!=3D0) > - net.inet.udp.gso - GSO enable on UDP communications (!=3D0) > > - for each interface: > - net.gso.dev."ifname=E2=80=9D.max_burst - GSO burst length lim= it > [default: IP_MAXPACKET=3D65535] > - net.gso.dev."ifname=E2=80=9D.enable_gso - GSO enable on =E2= =80=9Cifname=E2=80=9D > interface (!=3D0) > > - To show statistics: > - make sure that the GSO_STATS macro is defined in sys/net/gso.h > - use the simple gso-stats.c application to access the sysctl > net.gso.stats > that contains the address of the gsostats structure (defined in > gso.h) > which records the statistics. (compile with > -I/path/to/kernel/src/patched/) > -------------------------------------------------------------------------= ----------------------------------- > > -- > *Stefano Garzarella* > stefano.garzarella@gmail.com > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org= "