diff options
| author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2006-12-10 00:00:14 -0200 |
|---|---|---|
| committer | David S. Miller <davem@sunset.davemloft.net> | 2006-12-11 14:34:40 -0800 |
| commit | ff58629824c068e2a75402b5b83f12af0b36d394 (patch) | |
| tree | 0d8f4a64dbe4e52879cac33174df406adf77da44 /net | |
| parent | 45393a66a2c30fc8ed86e6c79a63a3cd5231c69f (diff) | |
| download | linux-ff58629824c068e2a75402b5b83f12af0b36d394.tar.bz2 | |
[DCCP] ccid3: Two optimisations for sending rate recomputation
This performs two optimisations for the recomputation of the sending rate.
1) Currently the target sending rate X_calc is recalculated whenever
a) the nofeedback timer expires, or
b) a feedback packet is received.
In the (a) case, recomputing X_calc is redundant, since
* the parameters p and RTT do not change in between the
reception of feedback packets;
* the parameter X_recv is either modified from received
feedback or via the nofeedback timer;
* a test (`p == 0') in the nofeedback timer avoids using
a stale/undefined value of X_calc if p was previously 0.
2) The nofeedback timer now only recomputes a timestamp when p == 0.
This is according to step (4) of [RFC 3448, 4.3] and avoids
unnecessarily determining a timestamp.
A debug statement about not updating X is also removed - it helps very
little in debugging and just clutters the logs.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Diffstat (limited to 'net')
| -rw-r--r-- | net/dccp/ccids/ccid3.c | 27 |
1 files changed, 16 insertions, 11 deletions
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index f1b745ee9cb6..92e893ee77c2 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -138,9 +138,6 @@ static void ccid3_hc_tx_update_x(struct sock *sk, struct timeval *now) const __u32 old_x = hctx->ccid3hctx_x; if (hctx->ccid3hctx_p > 0) { - hctx->ccid3hctx_x_calc = tfrc_calc_x(hctx->ccid3hctx_s, - hctx->ccid3hctx_rtt, - hctx->ccid3hctx_p); hctx->ccid3hctx_x = max_t(u32, min(hctx->ccid3hctx_x_calc, hctx->ccid3hctx_x_recv * 2), hctx->ccid3hctx_s / TFRC_T_MBI); @@ -152,8 +149,7 @@ static void ccid3_hc_tx_update_x(struct sock *sk, struct timeval *now) usecs_div(hctx->ccid3hctx_s, hctx->ccid3hctx_rtt) ); hctx->ccid3hctx_t_ld = *now; - } else - ccid3_pr_debug("Not changing X\n"); + } if (hctx->ccid3hctx_x != old_x) ccid3_update_send_time(hctx); @@ -223,9 +219,11 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) ccid3_pr_debug("%s, sk=%p, state=%s, not idle\n", dccp_role(sk), sk, ccid3_tx_state_name(hctx->ccid3hctx_state)); - /* Halve sending rate */ - /* If (p == 0 || X_calc > 2 * X_recv) + /* + * Modify the cached value of X_recv [RFC 3448, 4.4] + * + * If (p == 0 || X_calc > 2 * X_recv) * X_recv = max(X_recv / 2, s / (2 * t_mbi)); * Else * X_recv = X_calc / 4; @@ -233,14 +231,15 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) BUG_ON(hctx->ccid3hctx_p && !hctx->ccid3hctx_x_calc); if (hctx->ccid3hctx_p == 0 || - hctx->ccid3hctx_x_calc > 2 * hctx->ccid3hctx_x_recv) + hctx->ccid3hctx_x_calc > 2 * hctx->ccid3hctx_x_recv) { hctx->ccid3hctx_x_recv = max_t(u32, hctx->ccid3hctx_x_recv / 2, hctx->ccid3hctx_s / (2 * TFRC_T_MBI)); - else + if (hctx->ccid3hctx_p == 0) + dccp_timestamp(sk, &now); + } else hctx->ccid3hctx_x_recv = hctx->ccid3hctx_x_calc / 4; - /* Update sending rate */ - dccp_timestamp(sk, &now); + /* Now recalculate X [RFC 3448, 4.3, step (4)] */ ccid3_hc_tx_update_x(sk, &now); } /* @@ -496,6 +495,12 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) hctx->ccid3hctx_rtt = (9 * hctx->ccid3hctx_rtt + (u32)r_sample ) / 10; + /* Update sending rate (step 4 of [RFC 3448, 4.3]) */ + if (hctx->ccid3hctx_p > 0) + hctx->ccid3hctx_x_calc = + tfrc_calc_x(hctx->ccid3hctx_s, + hctx->ccid3hctx_rtt, + hctx->ccid3hctx_p); ccid3_hc_tx_update_x(sk, &now); ccid3_pr_debug("%s(%p), RTT=%uus (sample=%ldus), s=%u, " |