Hello, after the round of review on our v1 patch (you can find the relevant thread here [1]) we have improved our code of TCP Wave, a new congestion control algorithm.
Context: TCP Wave (TCPW) replaces the window-based transmission paradigm of the standard TCP with a burst-based transmission, the ACK-clock scheduling with a self-managed timer and the RTT-based congestion control loop with an Ack-based Capacity and Congestion Estimation (ACCE) module. In non-technical words, it sends data down the stack when a timer expires, and the timing of the received ACKs contribute to updating this timer regularly. We have left many debug messages to help people understand what is going on inside the module. We plan to remove almost all of them in the final submission. We added this new sender paradigm without deeply touching existing code; we re-used the existing infrastructure (TCP pacing timer, added with commit 218af599fa635b107cfe10acf3249c4dfe5e4123), thanks to the suggestion of Eric Dumazet. In fact, we only added four (optional) new congestion control functions: + /* get the expiration time for the pacing timer (optional) */ + u64 (*get_pacing_time)(struct sock *sk); + /* the pacing timer is expired (optional) */ + void (*pacing_timer_expired)(struct sock *sk); + /* get the # segs to send out when the timer expires (optional) */ + u32 (*get_segs_per_round)(struct sock *sk); + /* the TCP has sent some segments (optional) */ + void (*segments_sent)(struct sock *sk, u32 sent); to manage the previously mentioned pacing timer. With these functions, a congestion control can set the pacing time, be informed when it expires, indicate how many segments can leave when it expires, and know how many segments really left the TCP layer after it has expired. Thanks to the reviewers' suggestions we believe that the code has improved in clarity and performance. David Laight, Stephen Hemminger, David Miller, Neal Cardwell, Eric Dumazet, and all others that replied privately, thank you. Again, we would greatly appreciate any feedback, comments, suggestions, corrections and so on. Thank you for your attention. Cesare, Francesco, Ahmed, Natale [1] http://lists.openwall.net/netdev/2017/07/28/219 --- Changes in v2: - Using TCP pacing timer instead of adding a new one - Using ktime_t instead of jiffies to measure the time - Avoided the use of custom debug facilities - Cleaned the variable declarations Natale Patriciello (5): tcp: Added a function to retrieve pacing timer tcp: implemented pacing_expired tcp: added get_segs_per_round tcp: added segment sent wave: Added TCP Wave MAINTAINERS | 6 + include/net/tcp.h | 8 + include/uapi/linux/inet_diag.h | 13 + net/ipv4/Kconfig | 16 + net/ipv4/Makefile | 1 + net/ipv4/tcp_output.c | 61 ++- net/ipv4/tcp_wave.c | 1035 ++++++++++++++++++++++++++++++++++++++++ 7 files changed, 1127 insertions(+), 13 deletions(-) create mode 100644 net/ipv4/tcp_wave.c -- 2.14.2
