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[CCID3]: Inline for moving average

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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>
This commit is contained in:
Gerrit Renker 2007-11-20 18:09:59 -02:00 committed by David S. Miller
parent a5358fdc9c
commit c3ada46a00
2 changed files with 14 additions and 20 deletions
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25
net/dccp/ccids/ccid3.c
View file

@ -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; 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) if (hctx->ccid3hctx_s != old_s)
ccid3_update_send_interval(hctx); 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(); now = ktime_get_real();
/* /*
* Calculate new round trip sample as per [RFC 3448, 4.3] by * Calculate new RTT sample and update moving average
* R_sample = (now - t_recvdata) - t_elapsed
*/ */
r_sample = dccp_sample_rtt(sk, ktime_us_delta(now, packet->dccphtx_tstamp)); 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) { if (hctx->ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
/* /*
* Larger Initial Windows [RFC 4342, sec. 5] * Larger Initial Windows [RFC 4342, sec. 5]
*/ */
hctx->ccid3hctx_rtt = r_sample;
hctx->ccid3hctx_x = rfc3390_initial_rate(sk); hctx->ccid3hctx_x = rfc3390_initial_rate(sk);
hctx->ccid3hctx_t_ld = now; 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); ccid3_hc_tx_set_state(sk, TFRC_SSTATE_FBACK);
} else { } else {
hctx->ccid3hctx_rtt = (9 * hctx->ccid3hctx_rtt +
r_sample) / 10;
/* Update sending rate (step 4 of [RFC 3448, 4.3]) */ /* Update sending rate (step 4 of [RFC 3448, 4.3]) */
if (hctx->ccid3hctx_p > 0) 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) 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) */ if (likely(len > 0)) /* don't update on empty packets (e.g. ACKs) */
ccid3_pr_debug("Packet payload length is 0 - not updating\n"); hcrx->ccid3hcrx_s = tfrc_ewma(hcrx->ccid3hcrx_s, len, 9);
else
hcrx->ccid3hcrx_s = hcrx->ccid3hcrx_s == 0 ? len :
(9 * hcrx->ccid3hcrx_s + len) / 10;
} }
static void ccid3_hc_rx_send_feedback(struct sock *sk) static void ccid3_hc_rx_send_feedback(struct sock *sk)

9
net/dccp/ccids/lib/tfrc.h
View file

@ -37,6 +37,15 @@ static inline u32 scaled_div32(u64 a, u32 b)
return result; 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(u16 s, u32 R, u32 p);
extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue); extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue);