7e901ee7b6
During TCP fast recovery, the congestion control in charge is by default the Proportional Rate Reduction (PRR) unless the congestion control module specified otherwise (e.g. BBR). Previously when tcp_packets_in_flight() is below snd_ssthresh PRR would slow start upon receiving an ACK that 1) cumulatively acknowledges retransmitted data and 2) does not detect further lost retransmission Such conditions indicate the repair is in good steady progress after the first round trip of recovery. Otherwise PRR adopts the packet conservation principle to send only the amount that was newly delivered (indicated by this ACK). This patch generalizes the previous design principle to include also the newly sent data beside retransmission: as long as the delivery is making good progress, both retransmission and new data should be accounted to make PRR more cautious in slow starting. Suggested-by: Matt Mathis <mattmathis@google.com> Suggested-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20201031013412.1973112-1-ycheng@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.