Page MenuHomeFreeBSD
Files F144508440

D14141.id39264.diff
No OneTemporary
Actions

D14141.id39264.diff
View Options

Index: sys/netinet/cc/cc.h
===================================================================
--- sys/netinet/cc/cc.h
+++ sys/netinet/cc/cc.h
@@ -96,6 +96,8 @@
#define CCF_ACKNOW 0x0008 /* Will this ack be sent now? */
#define CCF_IPHDR_CE 0x0010 /* Does this packet set CE bit? */
#define CCF_TCPHDR_CWR 0x0020 /* Does this packet set CWR bit? */
+#define CCF_MAX_CWND 0x0040 /* Have we reached maximum cwnd? */
+#define CCF_CHG_MAX_CWND 0x0080 /* Cubic max_cwnd changed, for K */
/* ACK types passed to the ack_received() hook. */
#define CC_ACK 0x0001 /* Regular in sequence ACK. */
Index: sys/netinet/cc/cc_cubic.h
===================================================================
--- sys/netinet/cc/cc_cubic.h
+++ sys/netinet/cc/cc_cubic.h
@@ -39,6 +39,8 @@
#ifndef _NETINET_CC_CUBIC_H_
#define _NETINET_CC_CUBIC_H_
+#include <sys/limits.h>
+
/* Number of bits of precision for fixed point math calcs. */
#define CUBIC_SHIFT 8
@@ -160,8 +162,6 @@
/*
* Compute the new cwnd value using an implementation of eqn 1 from the I-D.
* Thanks to Kip Macy for help debugging this function.
- *
- * XXXLAS: Characterise bounds for overflow.
*/
static __inline unsigned long
cubic_cwnd(int ticks_since_cong, unsigned long wmax, uint32_t smss, int64_t K)
@@ -173,6 +173,15 @@
/* t - K, with CUBIC_SHIFT worth of precision. */
cwnd = ((int64_t)(ticks_since_cong << CUBIC_SHIFT) - (K * hz)) / hz;
+ /* moved this calculation up because it cannot overflow or underflow */
+ cwnd *= CUBIC_C_FACTOR * smss;
+
+ if (cwnd > 2097151) /* 2^21 cubed is long max */
+ return INT_MAX;
+
+ if (cwnd < -2097152) /* -2^21 cubed is long min */
+ return smss;
+
/* (t - K)^3, with CUBIC_SHIFT^3 worth of precision. */
cwnd *= (cwnd * cwnd);
@@ -181,8 +190,17 @@
* The down shift by CUBIC_SHIFT_4 is because cwnd has 4 lots of
* CUBIC_SHIFT included in the value. 3 from the cubing of cwnd above,
* and an extra from multiplying through by CUBIC_C_FACTOR.
+ *
+ * The original formula was this:
+ * cwnd = ((cwnd * CUBIC_C_FACTOR * smss) >> CUBIC_SHIFT_4) + wmax;
+ *
+ * CUBIC_C_FACTOR and smss factors were moved up to an earlier
+ * calculation to simplify overflow and underflow detection.
*/
- cwnd = ((cwnd * CUBIC_C_FACTOR * smss) >> CUBIC_SHIFT_4) + wmax;
+ cwnd = (cwnd >> CUBIC_SHIFT_4) + wmax;
+
+ if (cwnd < 0)
+ return 1;
return ((unsigned long)cwnd);
}
Index: sys/netinet/cc/cc_cubic.c
===================================================================
--- sys/netinet/cc/cc_cubic.c
+++ sys/netinet/cc/cc_cubic.c
@@ -86,6 +86,8 @@
unsigned long max_cwnd;
/* cwnd at the previous congestion event. */
unsigned long prev_max_cwnd;
+ /* Cached value for t_maxseg when K was computed */
+ uint32_t k_maxseg;
/* Number of congestion events. */
uint32_t num_cong_events;
/* Minimum observed rtt in ticks. */
@@ -122,6 +124,9 @@
cubic_data = ccv->cc_data;
cubic_record_rtt(ccv);
+ if (ccv->flags & CCF_MAX_CWND)
+ return;
+
/*
* Regular ACK and we're not in cong/fast recovery and we're cwnd
* limited and we're either not doing ABC or are slow starting or are
@@ -149,6 +154,12 @@
cubic_data->mean_rtt_ticks, cubic_data->max_cwnd,
CCV(ccv, t_maxseg));
+ if (ccv->flags & CCF_CHG_MAX_CWND || cubic_data->k_maxseg != CCV(ccv, t_maxseg)) {
+ cubic_data->K = cubic_k(cubic_data->max_cwnd / CCV(ccv, t_maxseg));
+ cubic_data->k_maxseg = CCV(ccv, t_maxseg);
+ ccv->flags &= ~(CCF_MAX_CWND|CCF_CHG_MAX_CWND);
+ }
+
w_cubic_next = cubic_cwnd(ticks_since_cong +
cubic_data->mean_rtt_ticks, cubic_data->max_cwnd,
CCV(ccv, t_maxseg), cubic_data->K);
@@ -160,13 +171,18 @@
* TCP-friendly region, follow tf
* cwnd growth.
*/
- CCV(ccv, snd_cwnd) = w_tf;
+ CCV(ccv, snd_cwnd) = ulmin(w_tf, TCP_MAXWIN << CCV(ccv, snd_scale));
else if (CCV(ccv, snd_cwnd) < w_cubic_next) {
/*
* Concave or convex region, follow CUBIC
* cwnd growth.
*/
+ if (w_cubic_next >= TCP_MAXWIN << CCV(ccv, snd_scale)) {
+ w_cubic_next = TCP_MAXWIN << CCV(ccv, snd_scale);
+ ccv->flags |= CCF_MAX_CWND;
+ }
+ w_cubic_next = ulmin(w_cubic_next, TCP_MAXWIN << CCV(ccv, snd_scale));
if (V_tcp_do_rfc3465)
CCV(ccv, snd_cwnd) = w_cubic_next;
else
@@ -184,8 +200,10 @@
* max_cwnd.
*/
if (cubic_data->num_cong_events == 0 &&
- cubic_data->max_cwnd < CCV(ccv, snd_cwnd))
+ cubic_data->max_cwnd < CCV(ccv, snd_cwnd)) {
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
+ ccv->flags |= CCF_CHG_MAX_CWND;
+ }
}
}
}
@@ -236,6 +254,7 @@
cubic_data->num_cong_events++;
cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
+ ccv->flags |= CCF_CHG_MAX_CWND;
}
ENTER_RECOVERY(CCV(ccv, t_flags));
}
@@ -248,6 +267,8 @@
cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
cubic_data->t_last_cong = ticks;
+ ccv->flags |= CCF_CHG_MAX_CWND;
+ ccv->flags &= ~CCF_MAX_CWND;
CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
ENTER_CONGRECOVERY(CCV(ccv, t_flags));
}
@@ -264,6 +285,7 @@
if (CCV(ccv, t_rxtshift) >= 2) {
cubic_data->num_cong_events++;
cubic_data->t_last_cong = ticks;
+ ccv->flags &= ~CCF_MAX_CWND;
}
break;
}
@@ -282,6 +304,7 @@
* get used.
*/
cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
+ ccv->flags |= CCF_CHG_MAX_CWND;
}
static int
@@ -306,9 +329,11 @@
pipe = 0;
/* Fast convergence heuristic. */
- if (cubic_data->max_cwnd < cubic_data->prev_max_cwnd)
+ if (cubic_data->max_cwnd < cubic_data->prev_max_cwnd) {
cubic_data->max_cwnd = (cubic_data->max_cwnd * CUBIC_FC_FACTOR)
>> CUBIC_SHIFT;
+ ccv->flags |= CCF_CHG_MAX_CWND;
+ }
if (IN_FASTRECOVERY(CCV(ccv, t_flags))) {
/*
@@ -331,6 +356,7 @@
cubic_data->max_cwnd) >> CUBIC_SHIFT));
}
cubic_data->t_last_cong = ticks;
+ ccv->flags &= ~CCF_MAX_CWND;
/* Calculate the average RTT between congestion epochs. */
if (cubic_data->epoch_ack_count > 0 &&
@@ -341,7 +367,6 @@
cubic_data->epoch_ack_count = 0;
cubic_data->sum_rtt_ticks = 0;
- cubic_data->K = cubic_k(cubic_data->max_cwnd / CCV(ccv, t_maxseg));
}
/*

File Metadata

Mime Type
text/plain
Expires
Tue, Feb 10, 12:04 AM (13 h, 3 m)
Storage Engine
blob
Storage Format
Raw Data
Storage Handle
28607589
Default Alt Text
D14141.id39264.diff (6 KB)

Event Timeline