Author: rscheff Date: Thu Sep 3 09:09:44 2020 New Revision: 365295 URL: https://svnweb.freebsd.org/changeset/base/365295
Log: MFC r364354: TCP Cubic: recalculate cwnd for every ACK. Since cubic calculates cwnd based on absolute time, retaining RFC3465 (ABC) once-per-window updates can lead to dramatic changes of cwnd in the convex region. Updating cwnd for each incoming ack minimizes this delta, preventing unintentional line-rate bursts. Reviewed by: chengc_netapp.com, tuexen (mentor) MFC after: 2 weeks Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D26060 Modified: stable/12/sys/netinet/cc/cc_cubic.c Modified: stable/12/sys/netinet/cc/cc_cubic.c ============================================================================== --- stable/12/sys/netinet/cc/cc_cubic.c Thu Sep 3 08:45:21 2020 (r365294) +++ stable/12/sys/netinet/cc/cc_cubic.c Thu Sep 3 09:09:44 2020 (r365295) @@ -131,16 +131,11 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type) cubic_record_rtt(ccv); /* - * Regular ACK and we're not in cong/fast recovery and we're cwnd - * 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. + * For a regular ACK and we're not in cong/fast recovery and + * we're cwnd limited, always recalculate cwnd. */ 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)))) { + (ccv->flags & CCF_CWND_LIMITED)) { /* 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) { @@ -193,15 +188,8 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type) * cwnd growth. * Only update snd_cwnd, if it doesn't shrink. */ - if (V_tcp_do_rfc3465) - CCV(ccv, snd_cwnd) = ulmin(w_cubic_next, - INT_MAX); - else - CCV(ccv, snd_cwnd) += ulmax(1, - ((ulmin(w_cubic_next, INT_MAX) - - CCV(ccv, snd_cwnd)) * - CCV(ccv, t_maxseg)) / - CCV(ccv, snd_cwnd)); + CCV(ccv, snd_cwnd) = ulmin(w_cubic_next, + INT_MAX); } /* _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
