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authorGerrit Renker <gerrit@erg.abdn.ac.uk>2007-11-20 18:09:59 -0200
committerDavid S. Miller <davem@davemloft.net>2008-01-28 14:54:43 -0800
commitc3ada46a009001e144b29736880962f24ee2afdf (patch)
treea475095e2ef5bff2f0d94a24ca94776578fe1c75
parenta5358fdc9c52e44d79dcd144375e089e166508d7 (diff)
[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>
-rw-r--r--net/dccp/ccids/ccid3.c25
-rw-r--r--net/dccp/ccids/lib/tfrc.h9
2 files changed, 14 insertions, 20 deletions
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 94a322863844..42893b1dfa09 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -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)
diff --git a/net/dccp/ccids/lib/tfrc.h b/net/dccp/ccids/lib/tfrc.h
index faf5f7e219e3..5a0ba86df183 100644
--- a/net/dccp/ccids/lib/tfrc.h
+++ b/net/dccp/ccids/lib/tfrc.h
@@ -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);