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[CCID3]: 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 uses a suggestion by Arnaldo as per http://www.mail-archive.com/dccp@vger.kernel.org/msg01662.html Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk> Signed-off-by: Ian McDonald <ian.mcdonald@jandi.co.nz> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -192,7 +192,7 @@ static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hctx, int len)
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{
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const u16 old_s = hctx->ccid3hctx_s;
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hctx->ccid3hctx_s = old_s == 0 ? len : (9 * old_s + len) / 10;
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hctx->ccid3hctx_s = tfrc_ewma(hctx->ccid3hctx_s, len, 9);
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if (hctx->ccid3hctx_s != old_s)
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ccid3_update_send_interval(hctx);
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@ -449,25 +449,15 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
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now = ktime_get_real();
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/*
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* Calculate new round trip sample as per [RFC 3448, 4.3] by
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* R_sample = (now - t_recvdata) - t_elapsed
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* Calculate new RTT sample and update moving average
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*/
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r_sample = dccp_sample_rtt(sk, ktime_us_delta(now, packet->dccphtx_tstamp));
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hctx->ccid3hctx_rtt = tfrc_ewma(hctx->ccid3hctx_rtt, r_sample, 9);
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/*
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* Update RTT estimate by
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* If (No feedback recv)
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* R = R_sample;
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* Else
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* R = q * R + (1 - q) * R_sample;
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*
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* q is a constant, RFC 3448 recomments 0.9
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*/
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if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
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/*
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* Larger Initial Windows [RFC 4342, sec. 5]
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*/
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hctx->ccid3hctx_rtt = r_sample;
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hctx->ccid3hctx_x = rfc3390_initial_rate(sk);
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hctx->ccid3hctx_t_ld = now;
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@ -481,8 +471,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
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ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
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} else {
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hctx->ccid3hctx_rtt = (9 * hctx->ccid3hctx_rtt +
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r_sample) / 10;
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/* Update sending rate (step 4 of [RFC 3448, 4.3]) */
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if (hctx->ccid3hctx_p > 0)
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@ -700,11 +688,8 @@ static void ccid3_hc_rx_set_state(struct sock *sk,
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static inline void ccid3_hc_rx_update_s(struct ccid3_hc_rx_sock *hcrx, int len)
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{
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if (unlikely(len == 0)) /* don't update on empty packets (e.g. ACKs) */
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ccid3_pr_debug("Packet payload length is 0 - not updating\n");
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else
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hcrx->ccid3hcrx_s = hcrx->ccid3hcrx_s == 0 ? len :
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(9 * hcrx->ccid3hcrx_s + len) / 10;
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if (likely(len > 0)) /* don't update on empty packets (e.g. ACKs) */
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hcrx->ccid3hcrx_s = tfrc_ewma(hcrx->ccid3hcrx_s, len, 9);
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}
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static void ccid3_hc_rx_send_feedback(struct sock *sk)
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@ -37,6 +37,15 @@ static inline u32 scaled_div32(u64 a, u32 b)
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return result;
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}
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/**
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* tfrc_ewma - Exponentially weighted moving average
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* @weight: Weight to be used as damping factor, in units of 1/10
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*/
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static inline u32 tfrc_ewma(const u32 avg, const u32 newval, const u8 weight)
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{
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return avg ? (weight * avg + (10 - weight) * newval) / 10 : newval;
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}
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extern u32 tfrc_calc_x(u16 s, u32 R, u32 p);
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extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue);
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