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Message-ID: <CAK6E8=eSYoxo6BLPh=jpmfudcRSJ3uT3YhZ0n-XP_dnxKCNH3A@mail.gmail.com> Date: Fri, 23 Oct 2015 23:11:00 -0700 From: Yuchung Cheng <ycheng@...gle.com> To: Bendik Rønning Opstad <bro.devel@...il.com> Cc: "David S. Miller" <davem@...emloft.net>, Alexey Kuznetsov <kuznet@....inr.ac.ru>, James Morris <jmorris@...ei.org>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, Patrick McHardy <kaber@...sh.net>, Jonathan Corbet <corbet@....net>, Eric Dumazet <edumazet@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, Tom Herbert <tom@...bertland.com>, Paolo Abeni <pabeni@...hat.com>, Erik Kline <ek@...gle.com>, Hannes Frederic Sowa <hannes@...essinduktion.org>, Al Viro <viro@...iv.linux.org.uk>, Jiri Pirko <jiri@...nulli.us>, Alexander Duyck <alexander.h.duyck@...hat.com>, Florian Westphal <fw@...len.de>, Daniel Lee <Longinus00@...il.com>, Marcelo Ricardo Leitner <mleitner@...hat.com>, Daniel Borkmann <daniel@...earbox.net>, Willem de Bruijn <willemb@...gle.com>, Linus Lüssing <linus.luessing@...3.blue>, linux-doc@...r.kernel.org, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, netdev <netdev@...r.kernel.org>, linux-api@...r.kernel.org, Andreas Petlund <apetlund@...ula.no>, Carsten Griwodz <griff@...ula.no>, Pål Halvorsen <paalh@...ula.no>, Jonas Markussen <jonassm@....uio.no>, Kristian Evensen <kristian.evensen@...il.com>, Kenneth Klette Jonassen <kennetkl@....uio.no>, Bendik Rønning Opstad <bro.devel+kernel@...il.com> Subject: Re: [PATCH RFC net-next 0/2] tcp: Redundant Data Bundling (RDB) On Fri, Oct 23, 2015 at 1:50 PM, Bendik Rønning Opstad <bro.devel@...il.com> wrote: > > This is a request for comments. > > Redundant Data Bundling (RDB) is a mechanism for TCP aimed at reducing > the latency for applications sending time-dependent data. > Latency-sensitive applications or services, such as online games and > remote desktop, produce traffic with thin-stream characteristics, > characterized by small packets and a relatively high ITT. By bundling > already sent data in packets with new data, RDB alleviates head-of-line > blocking by reducing the need to retransmit data segments when packets > are lost. RDB is a continuation on the work on latency improvements for > TCP in Linux, previously resulting in two thin-stream mechanisms in the > Linux kernel > (https://github.com/torvalds/linux/blob/master/Documentation/networking/tcp-thin.txt). > > The RDB implementation has been thoroughly tested, and shows > significant latency reductions when packet loss occurs[1]. The tests > show that, by imposing restrictions on the bundling rate, it can be made > not to negatively affect competing traffic in an unfair manner. > > Note: Current patch set depends on a recently submitted patch for > tcp_skb_cb (tcp: refactor struct tcp_skb_cb: http://patchwork.ozlabs.org/patch/510674) > > These patches have been tested with as set of packetdrill scripts located at > https://github.com/bendikro/packetdrill/tree/master/gtests/net/packetdrill/tests/linux/rdb > (The tests require patching packetdrill with a new socket option: > https://github.com/bendikro/packetdrill/commit/9916b6c53e33dd04329d29b7d8baf703b2c2ac1b) > > Detailed info about the RDB mechanism can be found at > http://mlab.no/blog/2015/10/redundant-data-bundling-in-tcp, as well as in the paper What's the difference between RDB and TCP repacketization (http://flylib.com/books/en/3.223.1.226/1/) ? Reading the blog page, I am concerned the amount of change (esp on fast path) just to bundle new writes during timeout & retransmit, for a specific type of application? why not just send X packets with total bytes < MSS on timeout.. > "Latency and Fairness Trade-Off for Thin Streams using Redundant Data > Bundling in TCP"[2]. > > [1] http://home.ifi.uio.no/paalh/students/BendikOpstad.pdf > [2] http://home.ifi.uio.no/bendiko/rdb_fairness_tradeoff.pdf > > > Bendik Rønning Opstad (2): > tcp: Add DPIFL thin stream detection mechanism > tcp: Add Redundant Data Bundling (RDB) > > Documentation/networking/ip-sysctl.txt | 23 +++ > include/linux/skbuff.h | 1 + > include/linux/tcp.h | 9 +- > include/net/tcp.h | 34 ++++ > include/uapi/linux/tcp.h | 1 + > net/core/skbuff.c | 3 +- > net/ipv4/Makefile | 3 +- > net/ipv4/sysctl_net_ipv4.c | 35 ++++ > net/ipv4/tcp.c | 19 ++- > net/ipv4/tcp_input.c | 3 + > net/ipv4/tcp_output.c | 11 +- > net/ipv4/tcp_rdb.c | 281 +++++++++++++++++++++++++++++++++ > 12 files changed, 415 insertions(+), 8 deletions(-) > create mode 100644 net/ipv4/tcp_rdb.c > > -- > 1.9.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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