Author: rscheff Date: Thu Aug 13 16:38:51 2020 New Revision: 364196 URL: https://svnweb.freebsd.org/changeset/base/364196
Log: TCP Cubic: After leaving slowstart fix unintended cwnd jump. Initializing K to zero in D23655 introduced a miscalculation, where cwnd would suddenly jump to cwnd_max instead of gradually increasing, after leaving slow-start. Properly calculating K instead of resetting it to zero resolves this issue. Also making sure, that cwnd is recalculated at the earliest opportunity once slow-start is over. Reported by: chengc_netapp.com Reviewed by: chengc_netapp.com, tuexen (mentor), rgrimes (mentor) Approved by: tuexen (mentor), rgrimes (mentor) MFC after: 3 weeks Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D25746 Modified: head/sys/netinet/cc/cc_cubic.c Modified: head/sys/netinet/cc/cc_cubic.c ============================================================================== --- head/sys/netinet/cc/cc_cubic.c Thu Aug 13 16:30:09 2020 (r364195) +++ head/sys/netinet/cc/cc_cubic.c Thu Aug 13 16:38:51 2020 (r364196) @@ -132,19 +132,29 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type) /* * Regular ACK and we're not in cong/fast recovery and we're cwnd - * limited and we're either not doing ABC or are slow starting or are - * doing ABC and we've sent a cwnd's worth of bytes. + * limited and we're either not doing ABC or are just coming out + * from slow-start or were application limited or are slow starting + * or are doing ABC and we've sent a cwnd's worth of bytes. */ if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) && (ccv->flags & CCF_CWND_LIMITED) && (!V_tcp_do_rfc3465 || + (cubic_data->flags & (CUBICFLAG_IN_SLOWSTART | CUBICFLAG_IN_APPLIMIT)) || CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh) || - (V_tcp_do_rfc3465 && ccv->flags & CCF_ABC_SENTAWND))) { + (V_tcp_do_rfc3465 && (ccv->flags & CCF_ABC_SENTAWND)))) { /* Use the logic in NewReno ack_received() for slow start. */ if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh) || cubic_data->min_rtt_ticks == TCPTV_SRTTBASE) { cubic_data->flags |= CUBICFLAG_IN_SLOWSTART; newreno_cc_algo.ack_received(ccv, type); } else { + if (cubic_data->flags & (CUBICFLAG_IN_SLOWSTART | + CUBICFLAG_IN_APPLIMIT)) { + cubic_data->flags &= ~(CUBICFLAG_IN_SLOWSTART | + CUBICFLAG_IN_APPLIMIT); + cubic_data->t_last_cong = ticks; + cubic_data->K = cubic_k(cubic_data->max_cwnd / + CCV(ccv, t_maxseg)); + } if ((ticks_since_cong = ticks - cubic_data->t_last_cong) < 0) { /* @@ -152,14 +162,6 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type) */ ticks_since_cong = INT_MAX; cubic_data->t_last_cong = ticks - INT_MAX; - } - - if (cubic_data->flags & (CUBICFLAG_IN_SLOWSTART | - CUBICFLAG_IN_APPLIMIT)) { - cubic_data->flags &= ~(CUBICFLAG_IN_SLOWSTART | - CUBICFLAG_IN_APPLIMIT); - cubic_data->t_last_cong = ticks; - cubic_data->K = 0; } /* * The mean RTT is used to best reflect the equations in _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
