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QUIC: switched to integer arithmetic in rtt calculations.

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RFC 9002 uses constants implying effective implementation,
i.e. using bit shift operations instead of floating point.
This commit is contained in:
Vladimir Homutov 2021-10-19 14:32:50 +03:00
parent 0cd45dea76
commit 12bda330d9
1 changed files with 17 additions and 8 deletions
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25
src/event/quic/ngx_event_quic_ack.c
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@ -14,17 +14,12 @@
/* RFC 9002, 6.1.1. Packet Threshold: kPacketThreshold */
#define NGX_QUIC_PKT_THR 3 /* packets */
/* RFC 9002, 6.1.2. Time Threshold: kTimeThreshold, kGranularity */
#define NGX_QUIC_TIME_THR 1.125
/* RFC 9002, 6.1.2. Time Threshold: kGranularity */
#define NGX_QUIC_TIME_GRANULARITY 1 /* ms */
/* RFC 9002, 7.6.1. Duration: kPersistentCongestionThreshold */
#define NGX_QUIC_PERSISTENT_CONGESTION_THR 3
#define ngx_quic_lost_threshold(qc) \
ngx_max(NGX_QUIC_TIME_THR * ngx_max((qc)->latest_rtt, (qc)->avg_rtt), \
NGX_QUIC_TIME_GRANULARITY)
/* send time of ACK'ed packets */
typedef struct {
@ -34,6 +29,7 @@ typedef struct {
} ngx_quic_ack_stat_t;
static ngx_inline ngx_msec_t ngx_quic_lost_threshold(ngx_quic_connection_t *qc);
static void ngx_quic_rtt_sample(ngx_connection_t *c, ngx_quic_ack_frame_t *ack,
enum ssl_encryption_level_t level, ngx_msec_t send_time);
static ngx_int_t ngx_quic_handle_ack_frame_range(ngx_connection_t *c,
@ -50,6 +46,19 @@ static void ngx_quic_congestion_lost(ngx_connection_t *c,
static void ngx_quic_lost_handler(ngx_event_t *ev);
/* RFC 9002, 6.1.2. Time Threshold: kTimeThreshold, kGranularity */
static ngx_inline ngx_msec_t
ngx_quic_lost_threshold(ngx_quic_connection_t *qc)
{
ngx_msec_t thr;
thr = ngx_max(qc->latest_rtt, qc->avg_rtt);
thr += thr >> 3;
return ngx_max(thr, NGX_QUIC_TIME_GRANULARITY);
}
ngx_int_t
ngx_quic_handle_ack_frame(ngx_connection_t *c, ngx_quic_header_t *pkt,
ngx_quic_frame_t *f)
@ -198,9 +207,9 @@ ngx_quic_rtt_sample(ngx_connection_t *c, ngx_quic_ack_frame_t *ack,
adjusted_rtt -= ack_delay;
}
qc->avg_rtt = 0.875 * qc->avg_rtt + 0.125 * adjusted_rtt;
qc->avg_rtt += (adjusted_rtt >> 3) - (qc->avg_rtt >> 3);
rttvar_sample = ngx_abs((ngx_msec_int_t) (qc->avg_rtt - adjusted_rtt));
qc->rttvar = 0.75 * qc->rttvar + 0.25 * rttvar_sample;
qc->rttvar += (rttvar_sample >> 2) - (qc->rttvar >> 2);
}
ngx_log_debug4(NGX_LOG_DEBUG_EVENT, c->log, 0,