diff options
| author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2007-09-25 22:39:16 -0700 |
|---|---|---|
| committer | David S. Miller <davem@sunset.davemloft.net> | 2007-10-10 16:52:34 -0700 |
| commit | aa97efd97acefb7d3dcd864adb878c7ce34061b3 (patch) | |
| tree | 1cad4e0193364c6b601c1ebc2ec8bc4aa8f600ae /net/dccp | |
| parent | e0eb68596232788bc352368f2fbc3cb088e42e41 (diff) | |
[DCCP]: Reuse ktime_get_real() calls again
This patch reduces the number of timestamps taken in the receive path
for each packet.
The ccid3_hc_tx_update_x() routine is called in
* the receive path for each CCID3-controlled packet
* for the nofeedback timer (if no feedback arrives during 4 RTT)
Currently, when there is no loss, each packet gets timestamped twice.
The patch resolves this by recycling the first timestamp taken on packet
reception for RTT sampling.
When the no_feedback_timer() is called, then the timestamp argument is
simply set to NULL - so that ccid3_hc_tx_update_x() takes care of the logic.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/dccp')
| -rw-r--r-- | net/dccp/ccids/ccid3.c | 39 |
1 files changed, 16 insertions, 23 deletions
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index e75efe72da2b..e16f9bb9eaaf 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -113,27 +113,24 @@ static inline void ccid3_update_send_interval(struct ccid3_hc_tx_sock *hctx) hctx->ccid3hctx_s, (unsigned)(hctx->ccid3hctx_x >> 6)); } -/* - * Update X by - * If (p > 0) - * X_calc = calcX(s, R, p); - * X = max(min(X_calc, 2 * X_recv), s / t_mbi); - * Else - * If (now - tld >= R) - * X = max(min(2 * X, 2 * X_recv), s / R); - * tld = now; + +/** + * ccid3_hc_tx_update_x - Update allowed sending rate X + * @stamp: most recent time if available - can be left NULL. + * This function tracks draft rfc3448bis, check there for latest details. * * Note: X and X_recv are both stored in units of 64 * bytes/second, to support * fine-grained resolution of sending rates. This requires scaling by 2^6 * throughout the code. Only X_calc is unscaled (in bytes/second). * */ -static void ccid3_hc_tx_update_x(struct sock *sk) +static void ccid3_hc_tx_update_x(struct sock *sk, ktime_t *stamp) { struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk); __u64 min_rate = 2 * hctx->ccid3hctx_x_recv; const __u64 old_x = hctx->ccid3hctx_x; + ktime_t now = stamp? *stamp : ktime_get_real(); /* * Handle IDLE periods: do not reduce below RFC3390 initial sending rate @@ -153,18 +150,14 @@ static void ccid3_hc_tx_update_x(struct sock *sk) (((__u64)hctx->ccid3hctx_s) << 6) / TFRC_T_MBI); - } else { - const ktime_t now = ktime_get_real(); - - if ((ktime_us_delta(now, hctx->ccid3hctx_t_ld) - - (s64)hctx->ccid3hctx_rtt) >= 0) { + } else if (ktime_us_delta(now, hctx->ccid3hctx_t_ld) + - (s64)hctx->ccid3hctx_rtt >= 0) { - hctx->ccid3hctx_x = - max(min(2 * hctx->ccid3hctx_x, min_rate), - scaled_div(((__u64)hctx->ccid3hctx_s) << 6, - hctx->ccid3hctx_rtt)); - hctx->ccid3hctx_t_ld = now; - } + hctx->ccid3hctx_x = + max(min(2 * hctx->ccid3hctx_x, min_rate), + scaled_div(((__u64)hctx->ccid3hctx_s) << 6, + hctx->ccid3hctx_rtt)); + hctx->ccid3hctx_t_ld = now; } if (hctx->ccid3hctx_x != old_x) { @@ -273,7 +266,7 @@ static void ccid3_hc_tx_no_feedback_timer(unsigned long data) hctx->ccid3hctx_x_recv <<= 4; } /* Now recalculate X [RFC 3448, 4.3, step (4)] */ - ccid3_hc_tx_update_x(sk); + ccid3_hc_tx_update_x(sk, NULL); /* * Schedule no feedback timer to expire in * max(t_RTO, 2 * s/X) = max(t_RTO, 2 * t_ipi) @@ -493,7 +486,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) tfrc_calc_x(hctx->ccid3hctx_s, hctx->ccid3hctx_rtt, hctx->ccid3hctx_p); - ccid3_hc_tx_update_x(sk); + ccid3_hc_tx_update_x(sk, &now); ccid3_pr_debug("%s(%p), RTT=%uus (sample=%uus), s=%u, " "p=%u, X_calc=%u, X_recv=%u, X=%u\n", |