mirror of https://gitee.com/openkylin/linux.git
d3b09995ab
When we increase the link tranmsit window we often observe the following scenario: 1) A STATE message bypasses a sequence of traffic packets and arrives far ahead of those to the receiver. STATE messages contain a 'peers_nxt_snt' field to indicate which was the last packet sent from the peer. This mechanism is intended as a last resort for the receiver to detect missing packets, e.g., during very low traffic when there is no packet flow to help early loss detection. 3) The receiving link compares the 'peer_nxt_snt' field to its own 'rcv_nxt', finds that there is a gap, and immediately sends a NACK message back to the peer. 4) When this NACKs arrives at the sender, all the requested retransmissions are performed, since it is a first-time request. Just like in the scenario described in the previous commit this leads to many redundant retransmissions, with decreased throughput as a consequence. We fix this by adding two more conditions before we send a NACK in this sitution. First, the deferred queue must be empty, so we cannot assume that the potential packet loss has already been detected by other means. Second, we check the 'peers_snd_nxt' field only in probe/ probe_reply messages, thus turning this into a true mechanism of last resort as it was really meant to be. Acked-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| README | ||
README
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.