commit 43f6f3fd3a85047fc7fc41e6ce8f924d007b98ee Author: Mike Perry <mikeperry-git@torproject.org> Date: Fri Jan 21 23:00:35 2022 +0000 Make N_EWMA a percentage of CWND update rate, capped by a max value. This proved better in Shadow sims than just a multiple of CWND. --- src/core/or/congestion_control_common.c | 56 ++++++++++++++++++++++----------- 1 file changed, 37 insertions(+), 19 deletions(-) diff --git a/src/core/or/congestion_control_common.c b/src/core/or/congestion_control_common.c index 93d3e54fcd..fb56014315 100644 --- a/src/core/or/congestion_control_common.c +++ b/src/core/or/congestion_control_common.c @@ -49,7 +49,9 @@ #define CWND_MAX_DFLT (INT32_MAX) #define BWE_SENDME_MIN_DFLT (5) -#define EWMA_CWND_COUNT_DFLT (2) + +#define N_EWMA_CWND_PCT_DFLT (50) +#define N_EWMA_MAX_DFLT (10) /* BDP algorithms for each congestion control algorithms use the piecewise * estimattor. See section 3.1.4 of proposal 324. */ @@ -98,7 +100,12 @@ static cc_alg_t cc_alg = CC_ALG_DFLT; /** * Number of cwnd worth of sendme acks to smooth RTT and BDP with, * using N_EWMA */ -static uint8_t ewma_cwnd_cnt; +static uint8_t n_ewma_cwnd_pct; + +/** + * Maximum number N for the N-count EWMA averaging of RTT and BDP. + */ +static uint8_t n_ewma_max; /** * Minimum number of sendmes before we begin BDP estimates @@ -174,14 +181,21 @@ congestion_control_new_consensus_params(const networkstatus_t *ns) BWE_SENDME_MIN_MIN, BWE_SENDME_MIN_MAX); -#define EWMA_CWND_COUNT_MIN 1 -#define EWMA_CWND_COUNT_MAX (100) - ewma_cwnd_cnt = - networkstatus_get_param(NULL, "cc_ewma_cwnd_cnt", - EWMA_CWND_COUNT_DFLT, - EWMA_CWND_COUNT_MIN, - EWMA_CWND_COUNT_MAX); - +#define N_EWMA_CWND_PCT_MIN 1 +#define N_EWMA_CWND_PCT_MAX (255) + n_ewma_cwnd_pct = + networkstatus_get_param(NULL, "cc_ewma_cwnd_pct", + N_EWMA_CWND_PCT_DFLT, + N_EWMA_CWND_PCT_MIN, + N_EWMA_CWND_PCT_MAX); + +#define N_EWMA_MAX_MIN 2 +#define N_EWMA_MAX_MAX (INT32_MAX) + n_ewma_max = + networkstatus_get_param(NULL, "cc_ewma_max", + N_EWMA_MAX_DFLT, + N_EWMA_MAX_MIN, + N_EWMA_MAX_MAX); } /** @@ -429,14 +443,19 @@ dequeue_timestamp(smartlist_t *timestamps_u64_usecs) } /** - * Returns the number of sendme acks that will be recieved in the - * current congestion window size, rounded to nearest int. + * Returns the number N of N-count EWMA, for averaging RTT and BDP over + * N SENDME acks. + * + * This N is bracketed between a divisor of the number of acks in a CWND + * and a max value. It is always at least 2. */ static inline uint64_t -sendme_acks_per_cwnd(const congestion_control_t *cc) +n_ewma_count(const congestion_control_t *cc) { - /* We add half a sendme_inc to cwnd to round to the nearest int */ - return ((cc->cwnd + cc->sendme_inc/2)/cc->sendme_inc); + uint64_t ewma_cnt = MIN(CWND_UPDATE_RATE(cc)*n_ewma_cwnd_pct/100, + n_ewma_max); + ewma_cnt = MAX(ewma_cnt, 2); + return ewma_cnt; } /** @@ -815,8 +834,7 @@ congestion_control_update_circuit_rtt(congestion_control_t *cc, return 0; } - ewma_cnt = ewma_cwnd_cnt*sendme_acks_per_cwnd(cc); - ewma_cnt = MAX(ewma_cnt, 2); // Use at least 2 + ewma_cnt = n_ewma_count(cc); cc->ewma_rtt_usec = n_count_ewma(rtt, cc->ewma_rtt_usec, ewma_cnt); @@ -939,7 +957,7 @@ congestion_control_update_circuit_bdp(congestion_control_t *cc, while (smartlist_len(cc->sendme_arrival_timestamps) > bwe_sendme_min && (uint64_t)smartlist_len(cc->sendme_arrival_timestamps) > - sendme_acks_per_cwnd(cc)) { + n_ewma_count(cc)) { (void)dequeue_timestamp(cc->sendme_arrival_timestamps); } int sendme_cnt = smartlist_len(cc->sendme_arrival_timestamps); @@ -966,7 +984,7 @@ congestion_control_update_circuit_bdp(congestion_control_t *cc, /* Calculate BDP_EWMA_COUNT N-EWMA */ cc->bdp[BDP_ALG_SENDME_RATE] = n_count_ewma(sendme_rate_bdp, cc->bdp[BDP_ALG_SENDME_RATE], - ewma_cwnd_cnt*sendme_acks_per_cwnd(cc)); + n_ewma_count(cc)); } }