Revert "dctcp: update cwnd on congestion event"
Neal Cardwell says: If I am reading the code correctly, then I would have two concerns: 1) Has that been tested? That seems like an extremely dramatic decrease in cwnd. For example, if the cwnd is 80, and there are 40 ACKs, and half the ACKs are ECE marked, then my back-of-the-envelope calculations seem to suggest that after just 11 ACKs the cwnd would be down to a minimal value of 2 [..] 2) That seems to contradict another passage in the draft [..] where it sazs: Just as specified in [RFC3168], DCTCP does not react to congestion indications more than once for every window of data. Neal is right. Fortunately we don't have to complicate this by testing vs. current rtt estimate, we can just revert the patch. Normal stack already handles this for us: receiving ACKs with ECE set causes a call to tcp_enter_cwr(), from there on the ssthresh gets adjusted and prr will take care of cwnd adjustment. Fixes: 47805667 ("dctcp: update cwnd on congestion event") Cc: Neal Cardwell <ncardwell@google.com> Signed-off-by:Florian Westphal <fw@strlen.de> Acked-by:
Neal Cardwell <ncardwell@google.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
parent
b1df0f5c
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