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Make N_EWMA a percentage of CWND update rate, capped by a max value.

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This proved better in Shadow sims than just a multiple of CWND.
This commit is contained in:
Mike Perry 2022-01-21 23:00:35 +00:00
parent 3079e2cacc
commit 43f6f3fd3a
1 changed files with 36 additions and 18 deletions
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54
src/core/or/congestion_control_common.c
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@ -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));
}
}