Author: sbruno
Date: Tue Jul 25 15:03:05 2017
New Revision: 321479
URL: https://svnweb.freebsd.org/changeset/base/321479

Log:
  Revert r308180 - Set slow start threshold more accurrately on loss ...
  
  This was discussed between various transport@ members and it was
  requested to be reverted and discussed.
  
  Submitted by: kevin
  Reported by:  lawerence
  Reviewed by:  hiren

Modified:
  head/sys/netinet/cc/cc_cdg.c
  head/sys/netinet/cc/cc_chd.c
  head/sys/netinet/cc/cc_dctcp.c
  head/sys/netinet/cc/cc_htcp.c
  head/sys/netinet/cc/cc_newreno.c
  head/sys/netinet/tcp_input.c

Modified: head/sys/netinet/cc/cc_cdg.c
==============================================================================
--- head/sys/netinet/cc/cc_cdg.c        Tue Jul 25 14:46:13 2017        
(r321478)
+++ head/sys/netinet/cc/cc_cdg.c        Tue Jul 25 15:03:05 2017        
(r321479)
@@ -474,9 +474,7 @@ cdg_cong_signal(struct cc_var *ccv, uint32_t signal_ty
                ENTER_RECOVERY(CCV(ccv, t_flags));
                break;
        case CC_RTO:
-               CCV(ccv, snd_ssthresh) =
-                   max((CCV(ccv, snd_max) - CCV(ccv, snd_una)) / 2 / mss, 2)
-                       * mss;
+               CCV(ccv, snd_ssthresh) = max(2*mss, cwin/2);
                CCV(ccv, snd_cwnd) = mss;
                break;
        default:

Modified: head/sys/netinet/cc/cc_chd.c
==============================================================================
--- head/sys/netinet/cc/cc_chd.c        Tue Jul 25 14:46:13 2017        
(r321478)
+++ head/sys/netinet/cc/cc_chd.c        Tue Jul 25 15:03:05 2017        
(r321479)
@@ -330,11 +330,13 @@ chd_cong_signal(struct cc_var *ccv, uint32_t signal_ty
        struct ertt *e_t;
        struct chd *chd_data;
        int qdly;
+       uint32_t cwin;
        u_int mss;
 
        e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
        chd_data = ccv->cc_data;
        qdly = imax(e_t->rtt, chd_data->maxrtt_in_rtt) - e_t->minrtt;
+       cwin = CCV(ccv, snd_cwnd);
        mss = CCV(ccv, t_maxseg);
 
        switch(signal_type) {
@@ -376,9 +378,7 @@ chd_cong_signal(struct cc_var *ccv, uint32_t signal_ty
                ENTER_FASTRECOVERY(CCV(ccv, t_flags));
                break;
        case CC_RTO:
-               CCV(ccv, snd_ssthresh) =
-                   max((CCV(ccv, snd_max) - CCV(ccv, snd_una)) / 2 / mss, 2)
-                       * mss;
+               CCV(ccv, snd_ssthresh) = max(2*mss, cwin/2);
                CCV(ccv, snd_cwnd) = mss;
                break;
 

Modified: head/sys/netinet/cc/cc_dctcp.c
==============================================================================
--- head/sys/netinet/cc/cc_dctcp.c      Tue Jul 25 14:46:13 2017        
(r321478)
+++ head/sys/netinet/cc/cc_dctcp.c      Tue Jul 25 15:03:05 2017        
(r321479)
@@ -230,21 +230,19 @@ static void
 dctcp_cong_signal(struct cc_var *ccv, uint32_t type)
 {
        struct dctcp *dctcp_data;
-       uint32_t cwin, ssthresh_on_loss;
+       uint32_t cwin;
        u_int mss;
 
        dctcp_data = ccv->cc_data;
        cwin = CCV(ccv, snd_cwnd);
        mss = CCV(ccv, t_maxseg);
-       ssthresh_on_loss =
-           max((CCV(ccv, snd_max) - CCV(ccv, snd_una)) / 2 / mss, 2)
-               * mss;
 
        switch (type) {
        case CC_NDUPACK:
                if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
                        if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
-                               CCV(ccv, snd_ssthresh) = ssthresh_on_loss;
+                               CCV(ccv, snd_ssthresh) = mss *
+                                   max(cwin / 2 / mss, 2);
                                dctcp_data->num_cong_events++;
                        } else {
                                /* cwnd has already updated as congestion
@@ -252,7 +250,8 @@ dctcp_cong_signal(struct cc_var *ccv, uint32_t type)
                                 * snd_cwnd_prev and recalculate snd_ssthresh
                                 */
                                cwin = CCV(ccv, snd_cwnd_prev);
-                               CCV(ccv, snd_ssthresh) = ssthresh_on_loss;
+                               CCV(ccv, snd_ssthresh) =
+                                   max(cwin / 2 / mss, 2) * mss;
                        }
                        ENTER_RECOVERY(CCV(ccv, t_flags));
                }
@@ -266,7 +265,8 @@ dctcp_cong_signal(struct cc_var *ccv, uint32_t type)
                if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
                        if (V_dctcp_slowstart &&
                            dctcp_data->num_cong_events++ == 0) {
-                               CCV(ccv, snd_ssthresh) = ssthresh_on_loss;
+                               CCV(ccv, snd_ssthresh) =
+                                   mss * max(cwin / 2 / mss, 2);
                                dctcp_data->alpha = MAX_ALPHA_VALUE;
                                dctcp_data->bytes_ecn = 0;
                                dctcp_data->bytes_total = 0;
@@ -285,7 +285,7 @@ dctcp_cong_signal(struct cc_var *ccv, uint32_t type)
                        dctcp_update_alpha(ccv);
                        dctcp_data->save_sndnxt += CCV(ccv, t_maxseg);
                        dctcp_data->num_cong_events++;
-                       CCV(ccv, snd_ssthresh) = ssthresh_on_loss;
+                       CCV(ccv, snd_ssthresh) = max(2 * mss, cwin / 2);
                        CCV(ccv, snd_cwnd) = mss;
                }
                break;

Modified: head/sys/netinet/cc/cc_htcp.c
==============================================================================
--- head/sys/netinet/cc/cc_htcp.c       Tue Jul 25 14:46:13 2017        
(r321478)
+++ head/sys/netinet/cc/cc_htcp.c       Tue Jul 25 15:03:05 2017        
(r321479)
@@ -325,9 +325,7 @@ htcp_cong_signal(struct cc_var *ccv, uint32_t type)
                 */
                if (CCV(ccv, t_rxtshift) >= 2)
                        htcp_data->t_last_cong = ticks;
-               CCV(ccv, snd_ssthresh) =
-                   max((CCV(ccv, snd_max) - CCV(ccv, snd_una)) / 2 / mss, 2)
-                       * mss;
+               CCV(ccv, snd_ssthresh) = max(2 * mss, cwin / 2);
                CCV(ccv, snd_cwnd) = mss;
                break;
        }
@@ -520,10 +518,6 @@ htcp_ssthresh_update(struct cc_var *ccv)
                CCV(ccv, snd_ssthresh) = ((u_long)CCV(ccv, snd_cwnd) *
                    htcp_data->beta) >> HTCP_SHIFT;
        }
-
-       /* Align ssthresh to MSS boundary */
-       CCV(ccv, snd_ssthresh) = (CCV(ccv, snd_ssthresh) / CCV(ccv, t_maxseg))
-           * CCV(ccv, t_maxseg);
 }
 
 

Modified: head/sys/netinet/cc/cc_newreno.c
==============================================================================
--- head/sys/netinet/cc/cc_newreno.c    Tue Jul 25 14:46:13 2017        
(r321478)
+++ head/sys/netinet/cc/cc_newreno.c    Tue Jul 25 15:03:05 2017        
(r321479)
@@ -182,26 +182,23 @@ newreno_after_idle(struct cc_var *ccv)
 static void
 newreno_cong_signal(struct cc_var *ccv, uint32_t type)
 {
-       uint32_t cwin, ssthresh_on_loss;
+       uint32_t cwin;
        u_int mss;
 
        cwin = CCV(ccv, snd_cwnd);
        mss = CCV(ccv, t_maxseg);
-       ssthresh_on_loss =
-           max((CCV(ccv, snd_max) - CCV(ccv, snd_una)) / 2 / mss, 2)
-               * mss;
 
        /* Catch algos which mistakenly leak private signal types. */
        KASSERT((type & CC_SIGPRIVMASK) == 0,
            ("%s: congestion signal type 0x%08x is private\n", __func__, type));
 
-       cwin = max(cwin / 2 / mss, 2) * mss;
+       cwin = max(2*mss, cwin/2);
 
        switch (type) {
        case CC_NDUPACK:
                if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
                        if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
-                               CCV(ccv, snd_ssthresh) = ssthresh_on_loss;
+                               CCV(ccv, snd_ssthresh) = cwin;
                                CCV(ccv, snd_cwnd) = cwin;
                        }
                        ENTER_RECOVERY(CCV(ccv, t_flags));
@@ -209,13 +206,13 @@ newreno_cong_signal(struct cc_var *ccv, uint32_t type)
                break;
        case CC_ECN:
                if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
-                       CCV(ccv, snd_ssthresh) = ssthresh_on_loss;
+                       CCV(ccv, snd_ssthresh) = cwin;
                        CCV(ccv, snd_cwnd) = cwin;
                        ENTER_CONGRECOVERY(CCV(ccv, t_flags));
                }
                break;
        case CC_RTO:
-               CCV(ccv, snd_ssthresh) = ssthresh_on_loss;
+               CCV(ccv, snd_ssthresh) = cwin;
                CCV(ccv, snd_cwnd) = mss;
                break;
        }

Modified: head/sys/netinet/tcp_input.c
==============================================================================
--- head/sys/netinet/tcp_input.c        Tue Jul 25 14:46:13 2017        
(r321478)
+++ head/sys/netinet/tcp_input.c        Tue Jul 25 15:03:05 2017        
(r321479)
@@ -441,8 +441,7 @@ cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, ui
                         * ssthresh = max (FlightSize / 2, 2*SMSS) eq (4)
                         */
                        tp->snd_ssthresh =
-                           max((tp->snd_max - tp->snd_una) / 2 / maxseg, 2)
-                               * maxseg;
+                           max((tp->snd_max - tp->snd_una) / 2, 2 * maxseg);
                        tp->snd_cwnd = maxseg;
                }
                break;
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