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Commit f5c2d636 authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
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[DCCP] ccid3: Simplify control flow in the calculation of t_ipi 

This patch performs a simplifying (performance) optimisation:

 In each call of the inline function ccid3_calc_new_t_ipi(), the state is
 tested against TFRC_SSTATE_NO_FBACK. This is expensive when the function
 is called very often. A simpler solution, implemented by this patch, is
 to adapt the control flow.

Background:
parent 90feeb95

net/dccp/ccids/ccid3.c

+3 −7
Original line number Diff line number Diff line
@@ -103,13 +103,7 @@ static void ccid3_hc_tx_set_state(struct sock *sk, 
/* 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)

{

	/*

	 * If no feedback spec says t_ipi is 1 second (set elsewhere and then

	 * doubles after every no feedback timer (separate function)

	 */

	if (hctx->ccid3hctx_state != TFRC_SSTATE_NO_FBACK)

		hctx->ccid3hctx_t_ipi = usecs_div(hctx->ccid3hctx_s,

						  hctx->ccid3hctx_x);

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

}



/* Calculate new delta by delta = min(t_ipi / 2, t_gran / 2) */
@@ -395,6 +389,8 @@ static void ccid3_hc_tx_packet_sent(struct sock *sk, int more, int len) 
				  "as a data packet",  dccp_role(sk));

		return;

	case TFRC_SSTATE_NO_FBACK:

		/* t_nom, t_ipi, delta do not change until feedback arrives */

		return;

	case TFRC_SSTATE_FBACK:

		if (len > 0) {

			timeval_sub_usecs(&hctx->ccid3hctx_t_nom,