Commit 43f6f3fd authored by Mike Perry's avatar Mike Perry
Browse files

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.
parent 3079e2ca

src/core/or/congestion_control_common.c

+37 −19
Original line number Diff line number Diff line
@@ -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));

      }

    }