git: b6c137de0af1 - main - tcp cc: re-organize newreno functions into parts that can be re-used
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Date: Tue, 17 Sep 2024 13:57:09 UTC
The branch main has been updated by cc:
URL: https://cgit.FreeBSD.org/src/commit/?id=b6c137de0af1a2bbd4c73bbc9cd96325268f3b0e
commit b6c137de0af1a2bbd4c73bbc9cd96325268f3b0e
Author: Cheng Cui <cc@FreeBSD.org>
AuthorDate: 2024-09-17 13:44:37 +0000
Commit: Cheng Cui <cc@FreeBSD.org>
CommitDate: 2024-09-17 13:54:17 +0000
tcp cc: re-organize newreno functions into parts that can be re-used
Reviewed by: rscheff, tuexen
Differential Revision: https://reviews.freebsd.org/D46046
---
sys/netinet/cc/cc.c | 188 ++++++++++++++++++++++++++++++++--------------------
sys/netinet/cc/cc.h | 3 +
2 files changed, 118 insertions(+), 73 deletions(-)
diff --git a/sys/netinet/cc/cc.c b/sys/netinet/cc/cc.c
index 16d27a868bd3..c628be250abf 100644
--- a/sys/netinet/cc/cc.c
+++ b/sys/netinet/cc/cc.c
@@ -449,15 +449,14 @@ newreno_cc_after_idle(struct cc_var *ccv)
}
/*
- * Perform any necessary tasks before we enter congestion recovery.
- */
-void
-newreno_cc_cong_signal(struct cc_var *ccv, ccsignal_t type)
+ * Get a new congestion window size on a multiplicative decrease event.
+ * */
+u_int
+newreno_cc_cwnd_on_multiplicative_decrease(struct cc_var *ccv, uint32_t mss)
{
- uint32_t cwin, factor, mss, pipe;
+ uint32_t cwin, factor;
cwin = CCV(ccv, snd_cwnd);
- mss = tcp_fixed_maxseg(ccv->tp);
/*
* Other TCP congestion controls use newreno_cong_signal(), but
* with their own private cc_data. Make sure the cc_data is used
@@ -465,12 +464,24 @@ newreno_cc_cong_signal(struct cc_var *ccv, ccsignal_t type)
*/
factor = V_newreno_beta;
+ return max(((uint64_t)cwin * (uint64_t)factor) / (100ULL * (uint64_t)mss), 2) * mss;
+}
+
+/*
+ * Perform any necessary tasks before we enter congestion recovery.
+ */
+void
+newreno_cc_cong_signal(struct cc_var *ccv, ccsignal_t type)
+{
+ uint32_t cwin, mss, pipe;
+
+ mss = tcp_fixed_maxseg(ccv->tp);
+
/* Catch algos which mistakenly leak private signal types. */
KASSERT((type & CC_SIGPRIVMASK) == 0,
("%s: congestion signal type 0x%08x is private\n", __func__, type));
- cwin = max(((uint64_t)cwin * (uint64_t)factor) / (100ULL * (uint64_t)mss),
- 2) * mss;
+ cwin = newreno_cc_cwnd_on_multiplicative_decrease(ccv, mss);
switch (type) {
case CC_NDUPACK:
@@ -506,78 +517,109 @@ newreno_cc_cong_signal(struct cc_var *ccv, ccsignal_t type)
}
}
-void
-newreno_cc_ack_received(struct cc_var *ccv, ccsignal_t type)
+u_int
+newreno_cc_cwnd_in_cong_avoid(struct cc_var *ccv)
{
- if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) &&
- (ccv->flags & CCF_CWND_LIMITED)) {
- u_int cw = CCV(ccv, snd_cwnd);
- u_int incr = CCV(ccv, t_maxseg);
+ u_int cw = CCV(ccv, snd_cwnd);
+ u_int incr = CCV(ccv, t_maxseg);
+
+ KASSERT(cw > CCV(ccv, snd_ssthresh),
+ ("congestion control state not in congestion avoidance\n"));
+ /*
+ * Regular in-order ACK, open the congestion window.
+ * The congestion control state we're in is congestion avoidance.
+ *
+ * Check if ABC (RFC 3465) is enabled.
+ * cong avoid: cwnd > ssthresh
+ *
+ * cong avoid and ABC (RFC 3465):
+ * Grow cwnd linearly by maxseg per RTT for each
+ * cwnd worth of ACKed data.
+ *
+ * cong avoid without ABC (RFC 5681):
+ * Grow cwnd linearly by approximately maxseg per RTT using
+ * maxseg^2 / cwnd per ACK as the increment.
+ * If cwnd > maxseg^2, fix the cwnd increment at 1 byte to
+ * avoid capping cwnd.
+ */
+ if (V_tcp_do_rfc3465) {
+ if (ccv->flags & CCF_ABC_SENTAWND)
+ ccv->flags &= ~CCF_ABC_SENTAWND;
+ else
+ incr = 0;
+ } else
+ incr = max((incr * incr / cw), 1);
+ /* ABC is on by default, so incr equals 0 frequently. */
+ if (incr > 0)
+ return min(cw + incr, TCP_MAXWIN << CCV(ccv, snd_scale));
+ else
+ return cw;
+}
+
+u_int
+newreno_cc_cwnd_in_slow_start(struct cc_var *ccv)
+{
+ u_int cw = CCV(ccv, snd_cwnd);
+ u_int incr = CCV(ccv, t_maxseg);
+
+ KASSERT(cw <= CCV(ccv, snd_ssthresh),
+ ("congestion control state not in slow start\n"));
+
+ /*
+ * Regular in-order ACK, open the congestion window.
+ * The congestion control state we're in is slow start.
+ *
+ * slow start: cwnd <= ssthresh
+ *
+ * slow start and ABC (RFC 3465):
+ * Grow cwnd exponentially by the amount of data
+ * ACKed capping the max increment per ACK to
+ * (abc_l_var * maxseg) bytes.
+ *
+ * slow start without ABC (RFC 5681):
+ * Grow cwnd exponentially by maxseg per ACK.
+ */
+ if (V_tcp_do_rfc3465) {
/*
- * Regular in-order ACK, open the congestion window.
- * Method depends on which congestion control state we're
- * in (slow start or cong avoid) and if ABC (RFC 3465) is
- * enabled.
- *
- * slow start: cwnd <= ssthresh
- * cong avoid: cwnd > ssthresh
- *
- * slow start and ABC (RFC 3465):
- * Grow cwnd exponentially by the amount of data
- * ACKed capping the max increment per ACK to
- * (abc_l_var * maxseg) bytes.
- *
- * slow start without ABC (RFC 5681):
- * Grow cwnd exponentially by maxseg per ACK.
- *
- * cong avoid and ABC (RFC 3465):
- * Grow cwnd linearly by maxseg per RTT for each
- * cwnd worth of ACKed data.
+ * In slow-start with ABC enabled and no RTO in sight?
+ * (Must not use abc_l_var > 1 if slow starting after
+ * an RTO. On RTO, snd_nxt = snd_una, so the
+ * snd_nxt == snd_max check is sufficient to
+ * handle this).
*
- * cong avoid without ABC (RFC 5681):
- * Grow cwnd linearly by approximately maxseg per RTT using
- * maxseg^2 / cwnd per ACK as the increment.
- * If cwnd > maxseg^2, fix the cwnd increment at 1 byte to
- * avoid capping cwnd.
+ * XXXLAS: Find a way to signal SS after RTO that
+ * doesn't rely on tcpcb vars.
*/
- if (cw > CCV(ccv, snd_ssthresh)) {
- if (V_tcp_do_rfc3465) {
- if (ccv->flags & CCF_ABC_SENTAWND)
- ccv->flags &= ~CCF_ABC_SENTAWND;
- else
- incr = 0;
- } else
- incr = max((incr * incr / cw), 1);
- } else if (V_tcp_do_rfc3465) {
- /*
- * In slow-start with ABC enabled and no RTO in sight?
- * (Must not use abc_l_var > 1 if slow starting after
- * an RTO. On RTO, snd_nxt = snd_una, so the
- * snd_nxt == snd_max check is sufficient to
- * handle this).
- *
- * XXXLAS: Find a way to signal SS after RTO that
- * doesn't rely on tcpcb vars.
- */
- uint16_t abc_val;
-
- if (ccv->flags & CCF_USE_LOCAL_ABC)
- abc_val = ccv->labc;
- else
- abc_val = V_tcp_abc_l_var;
- if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max))
- incr = min(ccv->bytes_this_ack,
- ccv->nsegs * abc_val *
- CCV(ccv, t_maxseg));
- else
- incr = min(ccv->bytes_this_ack, CCV(ccv, t_maxseg));
+ uint16_t abc_val;
+ if (ccv->flags & CCF_USE_LOCAL_ABC)
+ abc_val = ccv->labc;
+ else
+ abc_val = V_tcp_abc_l_var;
+ if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max))
+ incr = min(ccv->bytes_this_ack,
+ ccv->nsegs * abc_val * CCV(ccv, t_maxseg));
+ else
+ incr = min(ccv->bytes_this_ack, CCV(ccv, t_maxseg));
+ }
+ /* ABC is on by default, so incr equals 0 frequently. */
+ if (incr > 0)
+ return min(cw + incr, TCP_MAXWIN << CCV(ccv, snd_scale));
+ else
+ return cw;
+}
+
+void
+newreno_cc_ack_received(struct cc_var *ccv, ccsignal_t type)
+{
+ if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) &&
+ (ccv->flags & CCF_CWND_LIMITED)) {
+ if (CCV(ccv, snd_cwnd) > CCV(ccv, snd_ssthresh)) {
+ CCV(ccv, snd_cwnd) = newreno_cc_cwnd_in_cong_avoid(ccv);
+ } else {
+ CCV(ccv, snd_cwnd) = newreno_cc_cwnd_in_slow_start(ccv);
}
- /* ABC is on by default, so incr equals 0 frequently. */
- if (incr > 0)
- CCV(ccv, snd_cwnd) = min(cw + incr,
- TCP_MAXWIN << CCV(ccv, snd_scale));
}
}
diff --git a/sys/netinet/cc/cc.h b/sys/netinet/cc/cc.h
index d78c61bde2fe..890bea69a14b 100644
--- a/sys/netinet/cc/cc.h
+++ b/sys/netinet/cc/cc.h
@@ -231,6 +231,9 @@ void newreno_cc_post_recovery(struct cc_var *);
void newreno_cc_after_idle(struct cc_var *);
void newreno_cc_cong_signal(struct cc_var *, ccsignal_t);
void newreno_cc_ack_received(struct cc_var *, ccsignal_t);
+u_int newreno_cc_cwnd_on_multiplicative_decrease(struct cc_var *ccv, uint32_t mss);
+u_int newreno_cc_cwnd_in_cong_avoid(struct cc_var *ccv);
+u_int newreno_cc_cwnd_in_slow_start(struct cc_var *ccv);
/* Called to temporarily keep an algo from going away during change */
void cc_refer(struct cc_algo *algo);