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authorSangtae Ha <sha2@ncsu.edu>2008-03-04 17:17:41 -0500
committerDavid S. Miller <davem@davemloft.net>2008-03-04 17:17:41 -0500
commit6b3d626321c1d4ce9138a86b047dfafc6a403016 (patch)
tree0708e10ff8c603c014fa3c4ca88f7b51a2c0eb16 /net
parent7019b78e1483fa724dcba56e8465376b8fd03ea8 (diff)
[TCP]: TCP cubic v2.2
We have updated CUBIC to fix some issues with slow increase in large BDP networks. We also improved its convergence speed. The fix is in fact very simple -- the window increase limit of smax during the window probing phase (i.e., convex growth phase) is removed. We found that this does not affect TCP friendliness, but only improves its scalability. We have run some tests in our lab and also over the Internet path from NCSU to Japan. These results can be seen from the following page: http://netsrv.csc.ncsu.edu/wiki/index.php/Intra_protocol_fairness_testing_with_linux-2.6.23.9 http://netsrv.csc.ncsu.edu/wiki/index.php/RTT_fairness_testing_with_linux-2.6.23.9 http://netsrv.csc.ncsu.edu/wiki/index.php/TCP_friendliness_testing_with_linux-2.6.23.9 Signed-off-by: Sangtae Ha <sha2@ncsu.edu> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_cubic.c35
1 files changed, 8 insertions, 27 deletions
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 3aa0b23c1ea0..eb5b9854c8c7 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -1,12 +1,13 @@
1/* 1/*
2 * TCP CUBIC: Binary Increase Congestion control for TCP v2.1 2 * TCP CUBIC: Binary Increase Congestion control for TCP v2.2
3 * 3 * Home page:
4 * http://netsrv.csc.ncsu.edu/twiki/bin/view/Main/BIC
4 * This is from the implementation of CUBIC TCP in 5 * This is from the implementation of CUBIC TCP in
5 * Injong Rhee, Lisong Xu. 6 * Injong Rhee, Lisong Xu.
6 * "CUBIC: A New TCP-Friendly High-Speed TCP Variant 7 * "CUBIC: A New TCP-Friendly High-Speed TCP Variant
7 * in PFLDnet 2005 8 * in PFLDnet 2005
8 * Available from: 9 * Available from:
9 * http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/cubic-paper.pdf 10 * http://netsrv.csc.ncsu.edu/export/cubic-paper.pdf
10 * 11 *
11 * Unless CUBIC is enabled and congestion window is large 12 * Unless CUBIC is enabled and congestion window is large
12 * this behaves the same as the original Reno. 13 * this behaves the same as the original Reno.
@@ -20,15 +21,10 @@
20#define BICTCP_BETA_SCALE 1024 /* Scale factor beta calculation 21#define BICTCP_BETA_SCALE 1024 /* Scale factor beta calculation
21 * max_cwnd = snd_cwnd * beta 22 * max_cwnd = snd_cwnd * beta
22 */ 23 */
23#define BICTCP_B 4 /*
24 * In binary search,
25 * go to point (max+min)/N
26 */
27#define BICTCP_HZ 10 /* BIC HZ 2^10 = 1024 */ 24#define BICTCP_HZ 10 /* BIC HZ 2^10 = 1024 */
28 25
29static int fast_convergence __read_mostly = 1; 26static int fast_convergence __read_mostly = 1;
30static int max_increment __read_mostly = 16; 27static int beta __read_mostly = 717; /* = 717/1024 (BICTCP_BETA_SCALE) */
31static int beta __read_mostly = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */
32static int initial_ssthresh __read_mostly; 28static int initial_ssthresh __read_mostly;
33static int bic_scale __read_mostly = 41; 29static int bic_scale __read_mostly = 41;
34static int tcp_friendliness __read_mostly = 1; 30static int tcp_friendliness __read_mostly = 1;
@@ -40,9 +36,7 @@ static u64 cube_factor __read_mostly;
40/* Note parameters that are used for precomputing scale factors are read-only */ 36/* Note parameters that are used for precomputing scale factors are read-only */
41module_param(fast_convergence, int, 0644); 37module_param(fast_convergence, int, 0644);
42MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence"); 38MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence");
43module_param(max_increment, int, 0644); 39module_param(beta, int, 0644);
44MODULE_PARM_DESC(max_increment, "Limit on increment allowed during binary search");
45module_param(beta, int, 0444);
46MODULE_PARM_DESC(beta, "beta for multiplicative increase"); 40MODULE_PARM_DESC(beta, "beta for multiplicative increase");
47module_param(initial_ssthresh, int, 0644); 41module_param(initial_ssthresh, int, 0644);
48MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold"); 42MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
@@ -145,7 +139,7 @@ static u32 cubic_root(u64 a)
145static inline void bictcp_update(struct bictcp *ca, u32 cwnd) 139static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
146{ 140{
147 u64 offs; 141 u64 offs;
148 u32 delta, t, bic_target, min_cnt, max_cnt; 142 u32 delta, t, bic_target, max_cnt;
149 143
150 ca->ack_cnt++; /* count the number of ACKs */ 144 ca->ack_cnt++; /* count the number of ACKs */
151 145
@@ -211,19 +205,6 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd)
211 ca->cnt = 100 * cwnd; /* very small increment*/ 205 ca->cnt = 100 * cwnd; /* very small increment*/
212 } 206 }
213 207
214 if (ca->delay_min > 0) {
215 /* max increment = Smax * rtt / 0.1 */
216 min_cnt = (cwnd * HZ * 8)/(10 * max_increment * ca->delay_min);
217
218 /* use concave growth when the target is above the origin */
219 if (ca->cnt < min_cnt && t >= ca->bic_K)
220 ca->cnt = min_cnt;
221 }
222
223 /* slow start and low utilization */
224 if (ca->loss_cwnd == 0) /* could be aggressive in slow start */
225 ca->cnt = 50;
226
227 /* TCP Friendly */ 208 /* TCP Friendly */
228 if (tcp_friendliness) { 209 if (tcp_friendliness) {
229 u32 scale = beta_scale; 210 u32 scale = beta_scale;
@@ -391,4 +372,4 @@ module_exit(cubictcp_unregister);
391MODULE_AUTHOR("Sangtae Ha, Stephen Hemminger"); 372MODULE_AUTHOR("Sangtae Ha, Stephen Hemminger");
392MODULE_LICENSE("GPL"); 373MODULE_LICENSE("GPL");
393MODULE_DESCRIPTION("CUBIC TCP"); 374MODULE_DESCRIPTION("CUBIC TCP");
394MODULE_VERSION("2.1"); 375MODULE_VERSION("2.2");