Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a02ba041664171563e6418ccdf3b363d32d6a43b
Commit: a02ba041664171563e6418ccdf3b363d32d6a43b
Parent: 4ce61d1c7a8ef4c1337fa983a3036d4010e3c19e
Author: Stephen Hemminger <[EMAIL PROTECTED]>
AuthorDate: Thu May 17 00:04:18 2007 -0700
Committer: David S. Miller <[EMAIL PROTECTED]>
CommitDate: Thu May 17 14:20:31 2007 -0700
[TCP] slow start: Make comments and code logic clearer.
Add more comments to describe our version of tcp_slow_start().
Signed-off-by: Stephen Hemminger <[EMAIL PROTECTED]>
Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
---
net/ipv4/tcp_cong.c | 40 ++++++++++++++++++++++------------------
1 files changed, 22 insertions(+), 18 deletions(-)
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 86b2653..1260e52 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -276,30 +276,34 @@ int tcp_set_congestion_control(struct sock *sk, const
char *name)
/*
- * Slow start (exponential increase) with
- * RFC3742 Limited Slow Start (fast linear increase) support.
+ * Slow start is used when congestion window is less than slow start
+ * threshold. This version implements the basic RFC2581 version
+ * and optionally supports:
+ * RFC3742 Limited Slow Start - growth limited to max_ssthresh
+ * RFC3465 Appropriate Byte Counting - growth limited by bytes acknowledged
*/
void tcp_slow_start(struct tcp_sock *tp)
{
- int cnt = 0;
-
- if (sysctl_tcp_abc) {
- /* RFC3465: Slow Start
- * TCP sender SHOULD increase cwnd by the number of
- * previously unacknowledged bytes ACKed by each incoming
- * acknowledgment, provided the increase is not more than L
- */
- if (tp->bytes_acked < tp->mss_cache)
- return;
- }
+ int cnt; /* increase in packets */
+
+ /* RFC3465: ABC Slow start
+ * Increase only after a full MSS of bytes is acked
+ *
+ * TCP sender SHOULD increase cwnd by the number of
+ * previously unacknowledged bytes ACKed by each incoming
+ * acknowledgment, provided the increase is not more than L
+ */
+ if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache)
+ return;
- if (sysctl_tcp_max_ssthresh > 0 &&
- tp->snd_cwnd > sysctl_tcp_max_ssthresh)
- cnt += sysctl_tcp_max_ssthresh>>1;
+ if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd >
sysctl_tcp_max_ssthresh)
+ cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */
else
- cnt += tp->snd_cwnd;
+ cnt = tp->snd_cwnd; /* exponential increase
*/
- /* RFC3465: We MAY increase by 2 if discovered delayed ack */
+ /* RFC3465: ABC
+ * We MAY increase by 2 if discovered delayed ack
+ */
if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache)
cnt <<= 1;
tp->bytes_acked = 0;
-
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