[CCID 3]: Inline for moving average The moving average computation occurs so frequently in the CCID 3 code that it merits an inline function of its own. This is built on a suggestion by Arnaldo in http://www.mail-archive.com/dccp@xxxxxxxxxxxxxxx/msg01662.html Notes: ------ 1. The RTT estimate from the SYN exchange is now used when it is available, increasing initial accuracy of RTT estimator. 2. Shortened the statement for updating `s' a bit. Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx> --- net/dccp/ccids/ccid3.c | 25 +++++-------------------- net/dccp/ccids/lib/tfrc.h | 9 +++++++++ 2 files changed, 14 insertions(+), 20 deletions(-) --- a/net/dccp/ccids/lib/tfrc.h +++ b/net/dccp/ccids/lib/tfrc.h @@ -37,6 +37,15 @@ static inline u32 scaled_div32(u64 a, u3 return result; } +/** + * tfrc_ewma - Exponentially weighted moving average + * @weight: Weight to be used as damping factor, in units of 1/10 + */ +static inline u32 tfrc_ewma(const u32 avg, const u32 newval, const u8 weight) +{ + return avg? (weight * avg + (10 - weight) * newval) / 10 : newval; +} + extern u32 tfrc_calc_x(u16 s, u32 R, u32 p); extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue); --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -188,7 +188,7 @@ static inline void ccid3_hc_tx_update_s( { const u16 old_s = hctx->ccid3hctx_s; - hctx->ccid3hctx_s = old_s == 0 ? len : (9 * old_s + len) / 10; + hctx->ccid3hctx_s = tfrc_ewma(hctx->ccid3hctx_s, len, 9); if (hctx->ccid3hctx_s != old_s) ccid3_update_send_interval(hctx); @@ -461,25 +461,15 @@ static void ccid3_hc_tx_packet_recv(stru dccp_timestamp(sk, &now); /* - * Calculate new round trip sample as per [RFC 3448, 4.3] by - * R_sample = (now - t_recvdata) - t_elapsed + * Calculate new RTT sample and update moving average */ r_sample = dccp_sample_rtt(sk, &now, &packet->dccphtx_tstamp); + hctx->ccid3hctx_rtt = tfrc_ewma(hctx->ccid3hctx_rtt, r_sample, 9); - /* - * Update RTT estimate by - * If (No feedback recv) - * R = R_sample; - * Else - * R = q * R + (1 - q) * R_sample; - * - * q is a constant, RFC 3448 recomments 0.9 - */ if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) { /* * Larger Initial Windows [RFC 4342, sec. 5] */ - hctx->ccid3hctx_rtt = r_sample; hctx->ccid3hctx_x = rfc3390_initial_rate(sk); hctx->ccid3hctx_t_ld = now; @@ -493,8 +483,6 @@ static void ccid3_hc_tx_packet_recv(stru ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK); } else { - hctx->ccid3hctx_rtt = (9 * hctx->ccid3hctx_rtt + - r_sample) / 10; /* Update sending rate (step 4 of [RFC 3448, 4.3]) */ if (hctx->ccid3hctx_p > 0) @@ -720,11 +708,8 @@ static void ccid3_hc_rx_set_state(struct static inline void ccid3_hc_rx_update_s(struct ccid3_hc_rx_sock *hcrx, int len) { - if (unlikely(len == 0)) /* don't update on empty packets (e.g. ACKs) */ - ccid3_pr_debug("Packet payload length is 0 - not updating\n"); - else - hcrx->ccid3hcrx_s = hcrx->ccid3hcrx_s == 0 ? len : - (9 * hcrx->ccid3hcrx_s + len) / 10; + if (likely(len > 0)) /* don't update on empty packets (e.g. ACKs) */ + hcrx->ccid3hcrx_s = tfrc_ewma(hcrx->ccid3hcrx_s, len, 9); } static void ccid3_hc_rx_send_feedback(struct sock *sk) - To unsubscribe from this list: send the line "unsubscribe dccp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
