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Mat Martineau says: ==================== mptcp: Improve MPTCP-level window tracking This series improves MPTCP receive window compliance with RFC 8684 and helps increase throughput on high-speed links. Note that patch 3 makes a change in tcp_output.c For the details, Paolo says: I've been chasing bad/unstable performance with multiple subflows on very high speed links. It looks like the root cause is due to the current mptcp-level congestion window handling. There are apparently a few different sub-issues: - the rcv_wnd is not effectively shared on the tx side, as each subflow takes in account only the value received by the underlaying TCP connection. This is addressed in patch 1/5 - The mptcp-level offered wnd right edge is currently allowed to shrink. Reading section 3.3.4.: """ The receive window is relative to the DATA_ACK. As in TCP, a receiver MUST NOT shrink the right edge of the receive window (i.e., DATA_ACK + receive window). The receiver will use the data sequence number to tell if a packet should be accepted at the connection level. """ I read the above as we need to reflect window right-edge tracking on the wire, see patch 4/5. - The offered window right edge tracking can happen concurrently on multiple subflows, but there is no mutex protection. We need an additional atomic operation - still patch 4/5 This series additionally bumps a few new MIBs to track all the above (ensure/observe that the suspected races actually take place). I could not access again the host where the issue was so noticeable, still in the current setup the tput changes from [6-18] Gbps to 19Gbps very stable. ==================== Link: https://lore.kernel.org/r/20220504215408.349318-1-mathew.j.martineau@linux.intel.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.