Loading src/core/or/congestion_control_westwood.c 0 → 100644 +231 −0 Original line number Original line Diff line number Diff line /* Copyright (c) 2019-2021, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** * \file congestion_control_westwood.c * \brief Code that implements the TOR_WESTWOOD congestion control algorithm * from Proposal #324. */ #define TOR_CONGESTION_CONTROL_WESTWOOD_PRIVATE #include "core/or/or.h" #include "core/or/crypt_path.h" #include "core/or/or_circuit_st.h" #include "core/or/sendme.h" #include "core/or/congestion_control_st.h" #include "core/or/congestion_control_common.h" #include "core/or/congestion_control_westwood.h" #include "core/or/circuitlist.h" #include "core/or/circuituse.h" #include "core/or/origin_circuit_st.h" #include "core/or/channel.h" #include "feature/nodelist/networkstatus.h" #define USEC_ONE_MS (1000) #define WESTWOOD_CWND_BACKOFF_M 75 #define WESTWOOD_RTT_BACKOFF_M 100 #define WESTWOOD_RTT_THRESH 33 #define WESTWOOD_MIN_BACKOFF 0 /** * Cache westwood consensus parameters. */ void congestion_control_westwood_set_params(congestion_control_t *cc) { tor_assert(cc->cc_alg == CC_ALG_WESTWOOD); cc->westwood_params.cwnd_backoff_m = networkstatus_get_param(NULL, "cc_westwood_cwnd_m", WESTWOOD_CWND_BACKOFF_M, 0, 100); cc->westwood_params.rtt_backoff_m = networkstatus_get_param(NULL, "cc_westwood_rtt_m", WESTWOOD_RTT_BACKOFF_M, 50, 100); cc->westwood_params.rtt_thresh = networkstatus_get_param(NULL, "cc_westwood_rtt_thresh", WESTWOOD_RTT_THRESH, 0, 100); cc->westwood_params.min_backoff = networkstatus_get_param(NULL, "cc_westwood_min_backoff", WESTWOOD_MIN_BACKOFF, 0, 1); } /** * Return the RTT threshhold that signals congestion. * * Computed from the threshold parameter that specifies a * percent between the min and max RTT obseved so far. */ static inline uint64_t westwood_rtt_signal(const congestion_control_t *cc) { return ((100 - cc->westwood_params.rtt_thresh)*cc->min_rtt_usec + cc->westwood_params.rtt_thresh*(cc)->max_rtt_usec)/100; } /** * Compute a backoff to reduce the max RTT. * * This may be necessary to ensure that westwood does not have * a runaway condition where congestion inflates the max RTT, which * inflates the congestion threshold. That cannot happen with one * Westwood instance, but it may happen in aggregate. Hence, this is * a safety parameter, in case we need it. */ static inline uint64_t westwood_rtt_max_backoff(const congestion_control_t *cc) { return cc->min_rtt_usec + (cc->westwood_params.rtt_backoff_m * (cc->max_rtt_usec - cc->min_rtt_usec))/100; } /** * Returns true if the circuit is experiencing congestion, as per * TOR_WESTWOOD rules. */ static inline bool westwood_is_congested(const congestion_control_t *cc) { /* If the local channel is blocked, that is always congestion */ if (cc->blocked_chan) return true; /* If the min RTT is within 1ms of the signal, then there is not enough * range in RTTs to signify congestion. Treat that as not congested. */ if (westwood_rtt_signal(cc) < cc->min_rtt_usec || westwood_rtt_signal(cc) - cc->min_rtt_usec < USEC_ONE_MS) return false; /* If the EWMA-smoothed RTT exceeds the westwood RTT threshhold, * then it is congestion. */ if (cc->ewma_rtt_usec > westwood_rtt_signal(cc)) return true; return false; } /** * Process a SENDME and update the congestion window according to the * rules specified in TOR_WESTWOOD of Proposal #324. * * Essentially, this algorithm uses a threshhold of 'rtt_thresh', which * is a midpoint between the min and max RTT. If the RTT exceeds this * threshhold, then queue delay due to congestion is assumed to be present, * and the algirithm reduces the congestion window. If the RTT is below the * threshhold, the circuit is not congested (ie: queue delay is low), and we * increase the congestion window. * * The congestion window is updated only once every congestion window worth of * packets, even if the signal persists. It is also updated whenever the * upstream orcon blocks, or unblocks. This minimizes local client queues. */ int congestion_control_westwood_process_sendme(congestion_control_t *cc, const circuit_t *circ, const crypt_path_t *layer_hint) { tor_assert(cc && cc->cc_alg == CC_ALG_WESTWOOD); tor_assert(circ); /* Update ack counter until next congestion signal event is allowed */ if (cc->next_cc_event) cc->next_cc_event--; /* If we were unable to update our circuit estimates, Westwood must * *not* update its cwnd, otherwise it could run to infinity, or to 0. * Just update inflight from the sendme and return. */ if (!congestion_control_update_circuit_estimates(cc, circ, layer_hint)) { cc->inflight = cc->inflight - cc->sendme_inc; return 0; } /* We only update anything once per window */ if (cc->next_cc_event == 0) { if (!westwood_is_congested(cc)) { if (cc->in_slow_start) { cc->cwnd = MAX(cc->cwnd + CWND_INC_SS(cc), cc->bdp[cc->bdp_alg]); } else { cc->cwnd = cc->cwnd + CWND_INC(cc); } } else { if (cc->westwood_params.min_backoff) cc->cwnd = MIN(cc->cwnd*cc->westwood_params.cwnd_backoff_m/100, cc->bdp[cc->bdp_alg]); else cc->cwnd = MAX(cc->cwnd*cc->westwood_params.cwnd_backoff_m/100, cc->bdp[cc->bdp_alg]); cc->in_slow_start = 0; // Because Westwood's congestion can runaway and boost max rtt, // which increases its congestion signal, we backoff the max rtt // too. cc->max_rtt_usec = westwood_rtt_max_backoff(cc); log_info(LD_CIRC, "CC: TOR_WESTWOOD congestion. New max RTT: %"PRIu64, cc->max_rtt_usec/1000); } /* cwnd can never fall below 1 increment */ cc->cwnd = MAX(cc->cwnd, cc->cwnd_min); /* Schedule next update */ cc->next_cc_event = CWND_UPDATE_RATE(cc); if (CIRCUIT_IS_ORIGIN(circ)) { log_info(LD_CIRC, "CC: TOR_WESTWOOD Circuit %d " "CWND: %"PRIu64", " "INFL: %"PRIu64", " "NCCE: %"PRIu64", " "WRTT: %"PRIu64", " "WSIG: %"PRIu64", " "SS: %d", CONST_TO_ORIGIN_CIRCUIT(circ)->global_identifier, cc->cwnd, cc->inflight, cc->next_cc_event, cc->ewma_rtt_usec/1000, westwood_rtt_signal(cc)/1000, cc->in_slow_start ); } else { log_info(LD_CIRC, "CC: TOR_WESTWOOD Circuit %"PRIu64":%d " "CWND: %"PRIu64", " "INFL: %"PRIu64", " "NCCE: %"PRIu64", " "WRTT: %"PRIu64", " "WSIG: %"PRIu64", " "SS: %d", circ->n_chan->global_identifier, circ->n_circ_id, cc->cwnd, cc->inflight, cc->next_cc_event, cc->ewma_rtt_usec/1000, westwood_rtt_signal(cc)/1000, cc->in_slow_start ); } } /* Update inflight with ack */ cc->inflight = cc->inflight - cc->sendme_inc; return 0; } src/core/or/congestion_control_westwood.h 0 → 100644 +33 −0 Original line number Original line Diff line number Diff line /* Copyright (c) 2019-2021, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** * \file congestion_control_westwood.h * \brief Private-ish APIs for the TOR_WESTWOOD congestion control algorithm **/ #ifndef TOR_CONGESTION_CONTROL_WESTWOOD_H #define TOR_CONGESTION_CONTROL_WESTWOOD_H #include "core/or/crypt_path_st.h" #include "core/or/circuit_st.h" /* Processing SENDME cell. */ int congestion_control_westwood_process_sendme(struct congestion_control_t *cc, const circuit_t *circ, const crypt_path_t *layer_hint); void congestion_control_westwood_set_params(struct congestion_control_t *cc); /* Private section starts. */ #ifdef TOR_CONGESTION_CONTROL_WESTWOOD_PRIVATE /* * Unit tests declaractions. */ #ifdef TOR_UNIT_TESTS #endif /* defined(TOR_UNIT_TESTS) */ #endif /* defined(TOR_CONGESTION_CONTROL_WESTWOOD_PRIVATE) */ #endif /* !defined(TOR_CONGESTION_CONTROL_WESTWOOD_H) */ Loading
src/core/or/congestion_control_westwood.c 0 → 100644 +231 −0 Original line number Original line Diff line number Diff line /* Copyright (c) 2019-2021, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** * \file congestion_control_westwood.c * \brief Code that implements the TOR_WESTWOOD congestion control algorithm * from Proposal #324. */ #define TOR_CONGESTION_CONTROL_WESTWOOD_PRIVATE #include "core/or/or.h" #include "core/or/crypt_path.h" #include "core/or/or_circuit_st.h" #include "core/or/sendme.h" #include "core/or/congestion_control_st.h" #include "core/or/congestion_control_common.h" #include "core/or/congestion_control_westwood.h" #include "core/or/circuitlist.h" #include "core/or/circuituse.h" #include "core/or/origin_circuit_st.h" #include "core/or/channel.h" #include "feature/nodelist/networkstatus.h" #define USEC_ONE_MS (1000) #define WESTWOOD_CWND_BACKOFF_M 75 #define WESTWOOD_RTT_BACKOFF_M 100 #define WESTWOOD_RTT_THRESH 33 #define WESTWOOD_MIN_BACKOFF 0 /** * Cache westwood consensus parameters. */ void congestion_control_westwood_set_params(congestion_control_t *cc) { tor_assert(cc->cc_alg == CC_ALG_WESTWOOD); cc->westwood_params.cwnd_backoff_m = networkstatus_get_param(NULL, "cc_westwood_cwnd_m", WESTWOOD_CWND_BACKOFF_M, 0, 100); cc->westwood_params.rtt_backoff_m = networkstatus_get_param(NULL, "cc_westwood_rtt_m", WESTWOOD_RTT_BACKOFF_M, 50, 100); cc->westwood_params.rtt_thresh = networkstatus_get_param(NULL, "cc_westwood_rtt_thresh", WESTWOOD_RTT_THRESH, 0, 100); cc->westwood_params.min_backoff = networkstatus_get_param(NULL, "cc_westwood_min_backoff", WESTWOOD_MIN_BACKOFF, 0, 1); } /** * Return the RTT threshhold that signals congestion. * * Computed from the threshold parameter that specifies a * percent between the min and max RTT obseved so far. */ static inline uint64_t westwood_rtt_signal(const congestion_control_t *cc) { return ((100 - cc->westwood_params.rtt_thresh)*cc->min_rtt_usec + cc->westwood_params.rtt_thresh*(cc)->max_rtt_usec)/100; } /** * Compute a backoff to reduce the max RTT. * * This may be necessary to ensure that westwood does not have * a runaway condition where congestion inflates the max RTT, which * inflates the congestion threshold. That cannot happen with one * Westwood instance, but it may happen in aggregate. Hence, this is * a safety parameter, in case we need it. */ static inline uint64_t westwood_rtt_max_backoff(const congestion_control_t *cc) { return cc->min_rtt_usec + (cc->westwood_params.rtt_backoff_m * (cc->max_rtt_usec - cc->min_rtt_usec))/100; } /** * Returns true if the circuit is experiencing congestion, as per * TOR_WESTWOOD rules. */ static inline bool westwood_is_congested(const congestion_control_t *cc) { /* If the local channel is blocked, that is always congestion */ if (cc->blocked_chan) return true; /* If the min RTT is within 1ms of the signal, then there is not enough * range in RTTs to signify congestion. Treat that as not congested. */ if (westwood_rtt_signal(cc) < cc->min_rtt_usec || westwood_rtt_signal(cc) - cc->min_rtt_usec < USEC_ONE_MS) return false; /* If the EWMA-smoothed RTT exceeds the westwood RTT threshhold, * then it is congestion. */ if (cc->ewma_rtt_usec > westwood_rtt_signal(cc)) return true; return false; } /** * Process a SENDME and update the congestion window according to the * rules specified in TOR_WESTWOOD of Proposal #324. * * Essentially, this algorithm uses a threshhold of 'rtt_thresh', which * is a midpoint between the min and max RTT. If the RTT exceeds this * threshhold, then queue delay due to congestion is assumed to be present, * and the algirithm reduces the congestion window. If the RTT is below the * threshhold, the circuit is not congested (ie: queue delay is low), and we * increase the congestion window. * * The congestion window is updated only once every congestion window worth of * packets, even if the signal persists. It is also updated whenever the * upstream orcon blocks, or unblocks. This minimizes local client queues. */ int congestion_control_westwood_process_sendme(congestion_control_t *cc, const circuit_t *circ, const crypt_path_t *layer_hint) { tor_assert(cc && cc->cc_alg == CC_ALG_WESTWOOD); tor_assert(circ); /* Update ack counter until next congestion signal event is allowed */ if (cc->next_cc_event) cc->next_cc_event--; /* If we were unable to update our circuit estimates, Westwood must * *not* update its cwnd, otherwise it could run to infinity, or to 0. * Just update inflight from the sendme and return. */ if (!congestion_control_update_circuit_estimates(cc, circ, layer_hint)) { cc->inflight = cc->inflight - cc->sendme_inc; return 0; } /* We only update anything once per window */ if (cc->next_cc_event == 0) { if (!westwood_is_congested(cc)) { if (cc->in_slow_start) { cc->cwnd = MAX(cc->cwnd + CWND_INC_SS(cc), cc->bdp[cc->bdp_alg]); } else { cc->cwnd = cc->cwnd + CWND_INC(cc); } } else { if (cc->westwood_params.min_backoff) cc->cwnd = MIN(cc->cwnd*cc->westwood_params.cwnd_backoff_m/100, cc->bdp[cc->bdp_alg]); else cc->cwnd = MAX(cc->cwnd*cc->westwood_params.cwnd_backoff_m/100, cc->bdp[cc->bdp_alg]); cc->in_slow_start = 0; // Because Westwood's congestion can runaway and boost max rtt, // which increases its congestion signal, we backoff the max rtt // too. cc->max_rtt_usec = westwood_rtt_max_backoff(cc); log_info(LD_CIRC, "CC: TOR_WESTWOOD congestion. New max RTT: %"PRIu64, cc->max_rtt_usec/1000); } /* cwnd can never fall below 1 increment */ cc->cwnd = MAX(cc->cwnd, cc->cwnd_min); /* Schedule next update */ cc->next_cc_event = CWND_UPDATE_RATE(cc); if (CIRCUIT_IS_ORIGIN(circ)) { log_info(LD_CIRC, "CC: TOR_WESTWOOD Circuit %d " "CWND: %"PRIu64", " "INFL: %"PRIu64", " "NCCE: %"PRIu64", " "WRTT: %"PRIu64", " "WSIG: %"PRIu64", " "SS: %d", CONST_TO_ORIGIN_CIRCUIT(circ)->global_identifier, cc->cwnd, cc->inflight, cc->next_cc_event, cc->ewma_rtt_usec/1000, westwood_rtt_signal(cc)/1000, cc->in_slow_start ); } else { log_info(LD_CIRC, "CC: TOR_WESTWOOD Circuit %"PRIu64":%d " "CWND: %"PRIu64", " "INFL: %"PRIu64", " "NCCE: %"PRIu64", " "WRTT: %"PRIu64", " "WSIG: %"PRIu64", " "SS: %d", circ->n_chan->global_identifier, circ->n_circ_id, cc->cwnd, cc->inflight, cc->next_cc_event, cc->ewma_rtt_usec/1000, westwood_rtt_signal(cc)/1000, cc->in_slow_start ); } } /* Update inflight with ack */ cc->inflight = cc->inflight - cc->sendme_inc; return 0; }
src/core/or/congestion_control_westwood.h 0 → 100644 +33 −0 Original line number Original line Diff line number Diff line /* Copyright (c) 2019-2021, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** * \file congestion_control_westwood.h * \brief Private-ish APIs for the TOR_WESTWOOD congestion control algorithm **/ #ifndef TOR_CONGESTION_CONTROL_WESTWOOD_H #define TOR_CONGESTION_CONTROL_WESTWOOD_H #include "core/or/crypt_path_st.h" #include "core/or/circuit_st.h" /* Processing SENDME cell. */ int congestion_control_westwood_process_sendme(struct congestion_control_t *cc, const circuit_t *circ, const crypt_path_t *layer_hint); void congestion_control_westwood_set_params(struct congestion_control_t *cc); /* Private section starts. */ #ifdef TOR_CONGESTION_CONTROL_WESTWOOD_PRIVATE /* * Unit tests declaractions. */ #ifdef TOR_UNIT_TESTS #endif /* defined(TOR_UNIT_TESTS) */ #endif /* defined(TOR_CONGESTION_CONTROL_WESTWOOD_PRIVATE) */ #endif /* !defined(TOR_CONGESTION_CONTROL_WESTWOOD_H) */
