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tcp cc: re-organize newreno functions into parts that can be re-used
Reviewed by: rscheff, tuexen Differential Revision: https://reviews.freebsd.org/D46046
This commit is contained in:
Cheng Cui
parent
666303f598
commit
b6c137de0a
2 changed files with 119 additions and 74 deletions
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@ -449,15 +449,14 @@ newreno_cc_after_idle(struct cc_var *ccv)
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}
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/*
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* Perform any necessary tasks before we enter congestion recovery.
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*/
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void
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newreno_cc_cong_signal(struct cc_var *ccv, ccsignal_t type)
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* Get a new congestion window size on a multiplicative decrease event.
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* */
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u_int
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newreno_cc_cwnd_on_multiplicative_decrease(struct cc_var *ccv, uint32_t mss)
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{
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uint32_t cwin, factor, mss, pipe;
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uint32_t cwin, factor;
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cwin = CCV(ccv, snd_cwnd);
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mss = tcp_fixed_maxseg(ccv->tp);
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/*
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* Other TCP congestion controls use newreno_cong_signal(), but
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* with their own private cc_data. Make sure the cc_data is used
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@ -465,12 +464,24 @@ newreno_cc_cong_signal(struct cc_var *ccv, ccsignal_t type)
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*/
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factor = V_newreno_beta;
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return max(((uint64_t)cwin * (uint64_t)factor) / (100ULL * (uint64_t)mss), 2) * mss;
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}
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/*
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* Perform any necessary tasks before we enter congestion recovery.
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*/
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void
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newreno_cc_cong_signal(struct cc_var *ccv, ccsignal_t type)
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{
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uint32_t cwin, mss, pipe;
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mss = tcp_fixed_maxseg(ccv->tp);
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/* Catch algos which mistakenly leak private signal types. */
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KASSERT((type & CC_SIGPRIVMASK) == 0,
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("%s: congestion signal type 0x%08x is private\n", __func__, type));
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cwin = max(((uint64_t)cwin * (uint64_t)factor) / (100ULL * (uint64_t)mss),
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2) * mss;
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cwin = newreno_cc_cwnd_on_multiplicative_decrease(ccv, mss);
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switch (type) {
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case CC_NDUPACK:
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@ -506,78 +517,109 @@ newreno_cc_cong_signal(struct cc_var *ccv, ccsignal_t type)
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}
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}
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u_int
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newreno_cc_cwnd_in_cong_avoid(struct cc_var *ccv)
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{
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u_int cw = CCV(ccv, snd_cwnd);
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u_int incr = CCV(ccv, t_maxseg);
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KASSERT(cw > CCV(ccv, snd_ssthresh),
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("congestion control state not in congestion avoidance\n"));
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/*
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* Regular in-order ACK, open the congestion window.
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* The congestion control state we're in is congestion avoidance.
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*
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* Check if ABC (RFC 3465) is enabled.
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* cong avoid: cwnd > ssthresh
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*
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* cong avoid and ABC (RFC 3465):
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* Grow cwnd linearly by maxseg per RTT for each
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* cwnd worth of ACKed data.
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*
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* cong avoid without ABC (RFC 5681):
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* Grow cwnd linearly by approximately maxseg per RTT using
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* maxseg^2 / cwnd per ACK as the increment.
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* If cwnd > maxseg^2, fix the cwnd increment at 1 byte to
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* avoid capping cwnd.
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*/
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if (V_tcp_do_rfc3465) {
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if (ccv->flags & CCF_ABC_SENTAWND)
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ccv->flags &= ~CCF_ABC_SENTAWND;
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else
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incr = 0;
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} else
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incr = max((incr * incr / cw), 1);
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/* ABC is on by default, so incr equals 0 frequently. */
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if (incr > 0)
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return min(cw + incr, TCP_MAXWIN << CCV(ccv, snd_scale));
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else
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return cw;
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}
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u_int
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newreno_cc_cwnd_in_slow_start(struct cc_var *ccv)
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{
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u_int cw = CCV(ccv, snd_cwnd);
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u_int incr = CCV(ccv, t_maxseg);
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KASSERT(cw <= CCV(ccv, snd_ssthresh),
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("congestion control state not in slow start\n"));
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/*
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* Regular in-order ACK, open the congestion window.
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* The congestion control state we're in is slow start.
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*
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* slow start: cwnd <= ssthresh
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*
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* slow start and ABC (RFC 3465):
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* Grow cwnd exponentially by the amount of data
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* ACKed capping the max increment per ACK to
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* (abc_l_var * maxseg) bytes.
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*
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* slow start without ABC (RFC 5681):
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* Grow cwnd exponentially by maxseg per ACK.
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*/
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if (V_tcp_do_rfc3465) {
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/*
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* In slow-start with ABC enabled and no RTO in sight?
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* (Must not use abc_l_var > 1 if slow starting after
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* an RTO. On RTO, snd_nxt = snd_una, so the
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* snd_nxt == snd_max check is sufficient to
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* handle this).
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*
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* XXXLAS: Find a way to signal SS after RTO that
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* doesn't rely on tcpcb vars.
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*/
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uint16_t abc_val;
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if (ccv->flags & CCF_USE_LOCAL_ABC)
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abc_val = ccv->labc;
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else
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abc_val = V_tcp_abc_l_var;
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if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max))
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incr = min(ccv->bytes_this_ack,
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ccv->nsegs * abc_val * CCV(ccv, t_maxseg));
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else
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incr = min(ccv->bytes_this_ack, CCV(ccv, t_maxseg));
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}
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/* ABC is on by default, so incr equals 0 frequently. */
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if (incr > 0)
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return min(cw + incr, TCP_MAXWIN << CCV(ccv, snd_scale));
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else
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return cw;
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}
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void
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newreno_cc_ack_received(struct cc_var *ccv, ccsignal_t type)
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{
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if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) &&
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(ccv->flags & CCF_CWND_LIMITED)) {
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u_int cw = CCV(ccv, snd_cwnd);
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u_int incr = CCV(ccv, t_maxseg);
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/*
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* Regular in-order ACK, open the congestion window.
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* Method depends on which congestion control state we're
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* in (slow start or cong avoid) and if ABC (RFC 3465) is
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* enabled.
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*
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* slow start: cwnd <= ssthresh
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* cong avoid: cwnd > ssthresh
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*
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* slow start and ABC (RFC 3465):
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* Grow cwnd exponentially by the amount of data
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* ACKed capping the max increment per ACK to
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* (abc_l_var * maxseg) bytes.
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*
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* slow start without ABC (RFC 5681):
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* Grow cwnd exponentially by maxseg per ACK.
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*
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* cong avoid and ABC (RFC 3465):
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* Grow cwnd linearly by maxseg per RTT for each
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* cwnd worth of ACKed data.
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*
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* cong avoid without ABC (RFC 5681):
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* Grow cwnd linearly by approximately maxseg per RTT using
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* maxseg^2 / cwnd per ACK as the increment.
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* If cwnd > maxseg^2, fix the cwnd increment at 1 byte to
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* avoid capping cwnd.
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*/
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if (cw > CCV(ccv, snd_ssthresh)) {
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if (V_tcp_do_rfc3465) {
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if (ccv->flags & CCF_ABC_SENTAWND)
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ccv->flags &= ~CCF_ABC_SENTAWND;
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else
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incr = 0;
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} else
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incr = max((incr * incr / cw), 1);
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} else if (V_tcp_do_rfc3465) {
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/*
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* In slow-start with ABC enabled and no RTO in sight?
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* (Must not use abc_l_var > 1 if slow starting after
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* an RTO. On RTO, snd_nxt = snd_una, so the
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* snd_nxt == snd_max check is sufficient to
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* handle this).
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*
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* XXXLAS: Find a way to signal SS after RTO that
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* doesn't rely on tcpcb vars.
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*/
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uint16_t abc_val;
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if (ccv->flags & CCF_USE_LOCAL_ABC)
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abc_val = ccv->labc;
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else
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abc_val = V_tcp_abc_l_var;
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if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max))
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incr = min(ccv->bytes_this_ack,
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ccv->nsegs * abc_val *
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CCV(ccv, t_maxseg));
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else
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incr = min(ccv->bytes_this_ack, CCV(ccv, t_maxseg));
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if (CCV(ccv, snd_cwnd) > CCV(ccv, snd_ssthresh)) {
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CCV(ccv, snd_cwnd) = newreno_cc_cwnd_in_cong_avoid(ccv);
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} else {
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CCV(ccv, snd_cwnd) = newreno_cc_cwnd_in_slow_start(ccv);
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}
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/* ABC is on by default, so incr equals 0 frequently. */
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if (incr > 0)
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CCV(ccv, snd_cwnd) = min(cw + incr,
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TCP_MAXWIN << CCV(ccv, snd_scale));
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}
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}
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@ -231,6 +231,9 @@ void newreno_cc_post_recovery(struct cc_var *);
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void newreno_cc_after_idle(struct cc_var *);
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void newreno_cc_cong_signal(struct cc_var *, ccsignal_t);
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void newreno_cc_ack_received(struct cc_var *, ccsignal_t);
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u_int newreno_cc_cwnd_on_multiplicative_decrease(struct cc_var *ccv, uint32_t mss);
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u_int newreno_cc_cwnd_in_cong_avoid(struct cc_var *ccv);
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u_int newreno_cc_cwnd_in_slow_start(struct cc_var *ccv);
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/* Called to temporarily keep an algo from going away during change */
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void cc_refer(struct cc_algo *algo);
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