Commit 17893bc1 authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
Browse files

[DCCP] ccid3: Consistently update t_nom, t_ipi, t_delta 



This patch:

 * consolidates updating of parameters (t_nom, t_ipi, t_delta) which
   need to be updated at the same time, since they are inter-dependent

 * removes two inline functions which are no longer needed as a result of
   the above consolidation

 * resolves a FIXME regarding the re-calculation of t_ipi within the nofeedback
   timer, in the state where no feedback has previously been received

 * ties updating these parameters to updating the sending rate X, exploiting
   that all three parameters in turn depend on X; and using a small optimisation
   which can reduce the number of required instructions: only update the three
   parameters when X really changes

Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: default avatarIan McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@mandriva.com>
parent 48e03eee

net/dccp/ccids/ccid3.c

+17 −21
Original line number Diff line number Diff line
@@ -100,19 +100,24 @@ static void ccid3_hc_tx_set_state(struct sock *sk, 
	hctx->ccid3hctx_state = state;

}



/* Calculate new t_ipi (inter packet interval) by t_ipi = s / X_inst */

static inline void ccid3_calc_new_t_ipi(struct ccid3_hc_tx_sock *hctx)

/*

 * Recalculate scheduled nominal send time t_nom, inter-packet interval

 * t_ipi, and delta value. Should be called after each change to X.

 */

static inline void ccid3_update_send_time(struct ccid3_hc_tx_sock *hctx)

{

	timeval_sub_usecs(&hctx->ccid3hctx_t_nom, hctx->ccid3hctx_t_ipi);



	/* Calculate new t_ipi (inter packet interval) by t_ipi = s / X_inst */

	hctx->ccid3hctx_t_ipi = usecs_div(hctx->ccid3hctx_s, hctx->ccid3hctx_x);

}



	/* Update nominal send time with regard to the new t_ipi */

	timeval_add_usecs(&hctx->ccid3hctx_t_nom, hctx->ccid3hctx_t_ipi);



	/* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */

static inline void ccid3_calc_new_delta(struct ccid3_hc_tx_sock *hctx)

{

	hctx->ccid3hctx_delta = min_t(u32, hctx->ccid3hctx_t_ipi / 2,

					   TFRC_OPSYS_HALF_TIME_GRAN);

}



/*

 * Update X by

 *    If (p > 0)
@@ -126,6 +131,7 @@ static inline void ccid3_calc_new_delta(struct ccid3_hc_tx_sock *hctx) 
static void ccid3_hc_tx_update_x(struct sock *sk)

{

	struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);

	const __u32 old_x = hctx->ccid3hctx_x;



	/* To avoid large error in calcX */

	if (hctx->ccid3hctx_p >= TFRC_SMALLEST_P) {
@@ -149,6 +155,8 @@ static void ccid3_hc_tx_update_x(struct sock *sk) 
			hctx->ccid3hctx_t_ld = now;

		}

	}

	if (hctx->ccid3hctx_x != old_x)

		ccid3_update_send_time(hctx);

}



static void ccid3_hc_tx_no_feedback_timer(unsigned long data)
@@ -184,11 +192,7 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) 
		/* The value of R is still undefined and so we can not recompute

		 * the timout value. Keep initial value as per [RFC 4342, 5]. */

		next_tmout = TFRC_INITIAL_TIMEOUT;

		/*

		 * FIXME - not sure above calculation is correct. See section

		 * 5 of CCID3 11 should adjust tx_t_ipi and double that to

		 * achieve it really

		 */

		ccid3_update_send_time(hctx);

		break;

	case TFRC_SSTATE_FBACK:

		/*
@@ -479,17 +483,9 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) 
		/* unschedule no feedback timer */

		sk_stop_timer(sk, &hctx->ccid3hctx_no_feedback_timer);



		/* Update sending rate */

		/* Update sending rate (and likely t_ipi, t_nom, and delta) */

		ccid3_hc_tx_update_x(sk);



		/* Update next send time */

		timeval_sub_usecs(&hctx->ccid3hctx_t_nom,

				  hctx->ccid3hctx_t_ipi);

		ccid3_calc_new_t_ipi(hctx);

		timeval_add_usecs(&hctx->ccid3hctx_t_nom,

				  hctx->ccid3hctx_t_ipi);

		ccid3_calc_new_delta(hctx);



		/* remove all packets older than the one acked from history */

		dccp_tx_hist_purge_older(ccid3_tx_hist,

					 &hctx->ccid3hctx_hist, packet);

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