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Commit c3ada46a authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
Browse files

[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: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: default avatarIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a5358fdc

net/dccp/ccids/ccid3.c

+5 −20
Original line number Diff line number Diff line
@@ -192,7 +192,7 @@ static inline void ccid3_hc_tx_update_s(struct ccid3_hc_tx_sock *hctx, int len) 
{

	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);
@@ -449,25 +449,15 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) 


		now = ktime_get_real();

		/*

		 * 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, ktime_us_delta(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;
@@ -481,8 +471,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) 


			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)
@@ -700,11 +688,8 @@ static void ccid3_hc_rx_set_state(struct sock *sk, 


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)

net/dccp/ccids/lib/tfrc.h

+9 −0
Original line number Diff line number Diff line
@@ -37,6 +37,15 @@ static inline u32 scaled_div32(u64 a, u32 b) 
	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);