Merge pull request #1630 from private-octopus/bbr3-quantum-ratio

Port quantum ratio API to BBrv3

picoquic/bbr.c

@@ -221,6 +221,7 @@ typedef struct st_picoquic_bbr_state_t {
 
     /* Experimental extensions, may or maynot be a good idea. */
     uint64_t wifi_shadow_rtt; /* Shadow RTT used for wifi connections. */
+    double quantum_ratio; /* allow application to use a different default than 0.1% of bandwidth (or 1ms of traffic) */
 
 } picoquic_bbr_state_t;
 
@@ -392,6 +393,11 @@ static void BBROnInit(picoquic_bbr_state_t* bbr_state, picoquic_path_t* path_x,
     bbr_state->extra_acked_delivered = 0;
     /* Support for the wifi_shadow_rtt hack */
     bbr_state->wifi_shadow_rtt = path_x->cnx->quic->wifi_shadow_rtt;
+    /* Support for experimenting with the send_quantum ratio */
+    bbr_state->quantum_ratio = path_x->cnx->quic->bbr_quantum_ratio;
+    if (bbr_state->quantum_ratio == 0) {
+        bbr_state->quantum_ratio = 0.001;
+    }
 
     /* TODO, maybe: plug in the "shadow RTT".
      */
@@ -753,7 +759,7 @@ static void BBRSetSendQuantum(picoquic_bbr_state_t* bbr_state, picoquic_path_t*
         floor = 1 * path_x->send_mtu;
     }
     /* 1 ms = 1000000us/1000 */
-    bbr_state->send_quantum = (uint64_t)(bbr_state->pacing_rate / 1000.0); 
+    bbr_state->send_quantum = (uint64_t)(bbr_state->pacing_rate * bbr_state->quantum_ratio); 
     if (bbr_state->send_quantum > 0x10000) {
         bbr_state->send_quantum = 0x10000;
     }

picoquic/bbr1.c

@@ -279,6 +279,8 @@ typedef struct st_picoquic_bbr1_state_t {
     uint64_t cwin_before_suspension; /* So it can be restored if suspension stops. */
 
     uint64_t wifi_shadow_rtt; /* Shadow RTT used for wifi connections. */
+    double quantum_ratio;
+
     unsigned int filled_pipe : 1;
     unsigned int round_start : 1;
     unsigned int rt_prop_expired : 1;
@@ -337,7 +339,7 @@ void BBR1SetSendQuantum(picoquic_bbr1_state_t* bbr1_state, picoquic_path_t* path
         bbr1_state->send_quantum = 2ull * path_x->send_mtu;
     }
     else {
-        bbr1_state->send_quantum = (uint64_t)(bbr1_state->pacing_rate * 0.001);
+        bbr1_state->send_quantum = (uint64_t)(bbr1_state->pacing_rate * bbr1_state->quantum_ratio);
         if (bbr1_state->send_quantum > 0x10000) {
             bbr1_state->send_quantum = 0x10000;
         }
@@ -371,7 +373,11 @@ static void picoquic_bbr1_reset(picoquic_bbr1_state_t* bbr1_state, picoquic_path
     memset(bbr1_state, 0, sizeof(picoquic_bbr1_state_t));
     path_x->cwin = PICOQUIC_CWIN_INITIAL;
     bbr1_state->rt_prop = UINT64_MAX;
-    bbr1_state->wifi_shadow_rtt = wifi_shadow_rtt;
+    bbr1_state->wifi_shadow_rtt = path_x->cnx->quic->wifi_shadow_rtt;
+    bbr1_state->quantum_ratio = path_x->cnx->quic->bbr_quantum_ratio;
+    if (bbr1_state->quantum_ratio == 0) {
+        bbr1_state->quantum_ratio = 0.001;
+    }
 
     bbr1_state->rt_prop_stamp = current_time;
     bbr1_state->cycle_stamp = current_time;

picoquic/picoquic.h

@@ -1464,6 +1464,16 @@ void picoquic_set_congestion_algorithm(picoquic_cnx_t* cnx, picoquic_congestion_
  */
 void picoquic_set_default_wifi_shadow_rtt(picoquic_quic_t* quic, uint64_t wifi_shadow_rtt);
 
+/* The experimental API `picoquic_set_default_bbr_quantum_ratio`
+* allows application to change the "quantum ratio" parameter of the BBR
+* algorithm. The default value is 0.001 (1/1000th of the pacing rate
+* in bytes per second). Larger values like 0.01 would increase the
+* size of the "leaky bucket" used by the pacing algorithms. Whether
+* that's a good idea or not is debatable, probably depends on the
+* application.
+*/
+void picoquic_set_default_bbr_quantum_ratio(picoquic_quic_t* quic, double quantum_ratio);
+
 /* Bandwidth update and congestion control parameters value.
  * Congestion control in picoquic is characterized by three values:
  * - pacing rate, expressed in bytes per second (for example, 10Mbps would be noted as 1250000)

picoquic/picoquic_internal.h

@@ -669,6 +669,7 @@ typedef struct st_picoquic_quic_t {
 
     picoquic_congestion_algorithm_t const* default_congestion_alg;
     uint64_t wifi_shadow_rtt;
+    double bbr_quantum_ratio;
 
     struct st_picoquic_cnx_t* cnx_list;
     struct st_picoquic_cnx_t* cnx_last;

picoquic/quicctx.c

@@ -4528,6 +4528,11 @@ void picoquic_set_default_wifi_shadow_rtt(picoquic_quic_t* quic, uint64_t wifi_s
     quic->wifi_shadow_rtt = wifi_shadow_rtt;
 }
 
+void picoquic_set_default_bbr_quantum_ratio(picoquic_quic_t* quic, double quantum_ratio)
+{
+    quic->bbr_quantum_ratio = quantum_ratio;
+}
+
 void picoquic_subscribe_pacing_rate_updates(picoquic_cnx_t* cnx, uint64_t decrease_threshold, uint64_t increase_threshold)
 {
     cnx->pacing_decrease_threshold = decrease_threshold;