On Fri, Oct 23, 2015 at 1:50 PM, Bendik Rønning Opstad <bro.devel@xxxxxxxxx> 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-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
