Date: Wed, 24 Jun 2020 13:52:53 +0000 (UTC) From: Richard Scheffenegger <rscheff@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r362580 - head/sys/netinet/cc Message-ID: <202006241352.05ODqrZp045629@repo.freebsd.org>
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Author: rscheff Date: Wed Jun 24 13:52:53 2020 New Revision: 362580 URL: https://svnweb.freebsd.org/changeset/base/362580 Log: TCP: fix cubic RTO reaction. Proper TCP Cubic operation requires the knowledge of the maximum congestion window prior to the last congestion event. This restores and improves a bugfix previously added by jtl@ but subsequently removed due to a revert. Reported by: chengc_netapp.com Reviewed by: chengc_netapp.com, tuexen (mentor) Approved by: tuexen (mentor), rgrimes (mentor) MFC after: 2 weeks Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D25133 Modified: head/sys/netinet/cc/cc_cubic.c Modified: head/sys/netinet/cc/cc_cubic.c ============================================================================== --- head/sys/netinet/cc/cc_cubic.c Wed Jun 24 13:49:30 2020 (r362579) +++ head/sys/netinet/cc/cc_cubic.c Wed Jun 24 13:52:53 2020 (r362580) @@ -313,10 +313,15 @@ cubic_cong_signal(struct cc_var *ccv, uint32_t type) * timeout has fired more than once, as there is a reasonable * chance the first one is a false alarm and may not indicate * congestion. + * This will put Cubic firmly into the concave / TCP friendly + * region, for a slower ramp-up after two consecutive RTOs. */ if (CCV(ccv, t_rxtshift) >= 2) { cubic_data->flags |= CUBICFLAG_CONG_EVENT; cubic_data->t_last_cong = ticks; + cubic_data->max_cwnd = CCV(ccv, snd_cwnd_prev); + cubic_data->K = cubic_k(cubic_data->max_cwnd / + CCV(ccv, t_maxseg)); } break; }
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