diff options
Diffstat (limited to 'usr/src/uts/common/inet/cc/cc_cubic.c')
| -rw-r--r-- | usr/src/uts/common/inet/cc/cc_cubic.c | 79 |
1 files changed, 68 insertions, 11 deletions
diff --git a/usr/src/uts/common/inet/cc/cc_cubic.c b/usr/src/uts/common/inet/cc/cc_cubic.c index 11c238afd8..bb26a2358d 100644 --- a/usr/src/uts/common/inet/cc/cc_cubic.c +++ b/usr/src/uts/common/inet/cc/cc_cubic.c @@ -4,6 +4,7 @@ * All rights reserved. * Copyright (c) 2017 by Delphix. All rights reserved. * Copyright 2019 Joyent, Inc. + * Copyright 2020 RackTop Systems, Inc. * * This software was developed by Lawrence Stewart while studying at the Centre * for Advanced Internet Architectures, Swinburne University of Technology, made @@ -85,6 +86,7 @@ static void cubic_conn_init(struct cc_var *ccv); static void cubic_post_recovery(struct cc_var *ccv); static void cubic_record_rtt(struct cc_var *ccv); static void cubic_ssthresh_update(struct cc_var *ccv); +static void cubic_after_idle(struct cc_var *ccv); struct cubic { /* Cubic K in fixed point form with CUBIC_SHIFT worth of precision. */ @@ -115,6 +117,7 @@ struct cc_algo cubic_cc_algo = { .cong_signal = cubic_cong_signal, .conn_init = cubic_conn_init, .post_recovery = cubic_post_recovery, + .after_idle = cubic_after_idle, }; int @@ -129,7 +132,7 @@ _init(void) if ((err = mod_install(&cc_cubic_modlinkage)) != 0) (void) cc_deregister_algo(&cubic_cc_algo); } - cubic_cc_algo.after_idle = newreno_cc_algo->after_idle; + return (err); } @@ -195,19 +198,22 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type) * TCP-friendly region, follow tf * cwnd growth. */ - CCV(ccv, tcp_cwnd) = w_tf; + if (CCV(ccv, tcp_cwnd) < w_tf) + CCV(ccv, tcp_cwnd) = w_tf; } else if (CCV(ccv, tcp_cwnd) < w_cubic_next) { /* * Concave or convex region, follow CUBIC * cwnd growth. */ if (CC_ABC(ccv)) - CCV(ccv, tcp_cwnd) = w_cubic_next; + CCV(ccv, tcp_cwnd) = MIN(w_cubic_next, + INT_MAX); else - CCV(ccv, tcp_cwnd) += ((w_cubic_next - + CCV(ccv, tcp_cwnd) += MAX(1, + ((MIN(w_cubic_next, INT_MAX) - CCV(ccv, tcp_cwnd)) * CCV(ccv, tcp_mss)) / - CCV(ccv, tcp_cwnd); + CCV(ccv, tcp_cwnd)); } /* @@ -218,12 +224,34 @@ cubic_ack_received(struct cc_var *ccv, uint16_t type) * max_cwnd. */ if (cubic_data->num_cong_events == 0 && - cubic_data->max_cwnd < CCV(ccv, tcp_cwnd)) + cubic_data->max_cwnd < CCV(ccv, tcp_cwnd)) { cubic_data->max_cwnd = CCV(ccv, tcp_cwnd); + cubic_data->K = cubic_k(cubic_data->max_cwnd / + CCV(ccv, tcp_mss)); + } } } } +/* + * This is a Cubic specific implementation of after_idle. + * - Reset cwnd by calling New Reno implementation of after_idle. + * - Reset t_last_cong. + */ +static void +cubic_after_idle(struct cc_var *ccv) +{ + struct cubic *cubic_data; + + cubic_data = ccv->cc_data; + + cubic_data->max_cwnd = max(cubic_data->max_cwnd, CCV(ccv, tcp_cwnd)); + cubic_data->K = cubic_k(cubic_data->max_cwnd / CCV(ccv, tcp_mss)); + + newreno_cc_algo->after_idle(ccv); + cubic_data->t_last_cong = gethrtime(); +} + static void cubic_cb_destroy(struct cc_var *ccv) { @@ -237,7 +265,7 @@ cubic_cb_init(struct cc_var *ccv) { struct cubic *cubic_data; - cubic_data = kmem_alloc(sizeof (struct cubic), KM_NOSLEEP); + cubic_data = kmem_zalloc(sizeof (struct cubic), KM_NOSLEEP); if (cubic_data == NULL) return (ENOMEM); @@ -330,6 +358,7 @@ static void cubic_post_recovery(struct cc_var *ccv) { struct cubic *cubic_data; + uint32_t mss, pipe; cubic_data = ccv->cc_data; @@ -339,11 +368,39 @@ cubic_post_recovery(struct cc_var *ccv) >> CUBIC_SHIFT; } + /* + * There is a risk that if the cwnd becomes less than mss, and + * we do not get enough acks to drive it back up beyond mss, + * we will stop transmitting data altogether. + * + * The Cubic RFC defines values in terms of units of mss. Therefore + * we must make sure we have at least 1 mss to make progress + * since the algorthm is written that way. + */ + mss = CCV(ccv, tcp_mss); + if (IN_FASTRECOVERY(ccv->flags)) { - /* Update cwnd based on beta and adjusted max_cwnd. */ - CCV(ccv, tcp_cwnd) = max(1, ((CUBIC_BETA * - cubic_data->max_cwnd) >> CUBIC_SHIFT)); + /* + * If inflight data is less than ssthresh, set cwnd + * conservatively to avoid a burst of data, as suggested in + * the NewReno RFC. Otherwise, use the CUBIC method. + */ + pipe = CCV(ccv, tcp_snxt) - CCV(ccv, tcp_suna); + if (pipe < CCV(ccv, tcp_cwnd_ssthresh)) { + /* + * Ensure that cwnd does not collapse to 1 MSS under + * adverse conditions. Implements RFC6582 + */ + CCV(ccv, tcp_cwnd) = MAX(pipe, mss) + mss; + } else { + /* Update cwnd based on beta and adjusted max_cwnd. */ + CCV(ccv, tcp_cwnd) = max(mss, ((CUBIC_BETA * + cubic_data->max_cwnd) >> CUBIC_SHIFT)); + } + } else { + CCV(ccv, tcp_cwnd) = max(mss, CCV(ccv, tcp_cwnd)); } + cubic_data->t_last_cong = gethrtime(); /* Calculate the average RTT between congestion epochs. */ @@ -355,7 +412,7 @@ cubic_post_recovery(struct cc_var *ccv) cubic_data->epoch_ack_count = 0; cubic_data->sum_rtt_nsecs = 0; - cubic_data->K = cubic_k(cubic_data->max_cwnd / CCV(ccv, tcp_mss)); + cubic_data->K = cubic_k(cubic_data->max_cwnd / mss); } /* |