netdev - [PATCH RFC v2 net-next 0/2] tcp: Redundant Data Bundling (RDB)

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Date:	Mon, 23 Nov 2015 17:26:24 +0100
From:	"Bendik Rønning Opstad" <bro.devel@...il.com>
To:	"David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>
Cc:	Yuchung Cheng <ycheng@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	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: [PATCH RFC v2 net-next 0/2] tcp: Redundant Data Bundling (RDB)

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
"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

Changes:

v2:
 * tcp-Add-DPIFL-thin-stream-detection-mechanism:
   * Change calculation in tcp_stream_is_thin_dpifl based on
     feedback from Eric Dumazet.

 * tcp-Add-Redundant-Data-Bundling-RDB:
   * Removed setting nonagle in do_tcp_setsockopt (TCP_RDB)
     to reduce complexity as commented by Neal Cardwell.
   * Cleaned up loss detection code in rdb_check_rtx_queue_loss

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                    |   3 +-
 include/net/tcp.h                      |  35 +++++
 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                         |  16 +-
 net/ipv4/tcp_input.c                   |   3 +
 net/ipv4/tcp_output.c                  |  11 +-
 net/ipv4/tcp_rdb.c                     | 271 +++++++++++++++++++++++++++++++++
 12 files changed, 397 insertions(+), 8 deletions(-)
 create mode 100644 net/ipv4/tcp_rdb.c

-- 
1.9.1

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