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400031e05a
Now that we have the __bpf_kfunc tag, we should use add it to all existing kfuncs to ensure that they'll never be elided in LTO builds. Signed-off-by: David Vernet <void@manifault.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Stanislav Fomichev <sdf@google.com> Link: https://lore.kernel.org/bpf/20230201173016.342758-4-void@manifault.com
307 lines
8.6 KiB
C
307 lines
8.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* DataCenter TCP (DCTCP) congestion control.
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*
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* http://simula.stanford.edu/~alizade/Site/DCTCP.html
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*
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* This is an implementation of DCTCP over Reno, an enhancement to the
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* TCP congestion control algorithm designed for data centers. DCTCP
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* leverages Explicit Congestion Notification (ECN) in the network to
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* provide multi-bit feedback to the end hosts. DCTCP's goal is to meet
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* the following three data center transport requirements:
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*
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* - High burst tolerance (incast due to partition/aggregate)
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* - Low latency (short flows, queries)
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* - High throughput (continuous data updates, large file transfers)
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* with commodity shallow buffered switches
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*
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* The algorithm is described in detail in the following two papers:
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*
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* 1) Mohammad Alizadeh, Albert Greenberg, David A. Maltz, Jitendra Padhye,
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* Parveen Patel, Balaji Prabhakar, Sudipta Sengupta, and Murari Sridharan:
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* "Data Center TCP (DCTCP)", Data Center Networks session
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* Proc. ACM SIGCOMM, New Delhi, 2010.
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* http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf
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*
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* 2) Mohammad Alizadeh, Adel Javanmard, and Balaji Prabhakar:
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* "Analysis of DCTCP: Stability, Convergence, and Fairness"
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* Proc. ACM SIGMETRICS, San Jose, 2011.
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* http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp_analysis-full.pdf
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*
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* Initial prototype from Abdul Kabbani, Masato Yasuda and Mohammad Alizadeh.
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*
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* Authors:
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*
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* Daniel Borkmann <dborkman@redhat.com>
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* Florian Westphal <fw@strlen.de>
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* Glenn Judd <glenn.judd@morganstanley.com>
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*/
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#include <linux/btf.h>
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#include <linux/btf_ids.h>
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#include <linux/module.h>
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#include <linux/mm.h>
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#include <net/tcp.h>
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#include <linux/inet_diag.h>
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#include "tcp_dctcp.h"
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#define DCTCP_MAX_ALPHA 1024U
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struct dctcp {
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u32 old_delivered;
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u32 old_delivered_ce;
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u32 prior_rcv_nxt;
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u32 dctcp_alpha;
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u32 next_seq;
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u32 ce_state;
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u32 loss_cwnd;
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struct tcp_plb_state plb;
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};
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static unsigned int dctcp_shift_g __read_mostly = 4; /* g = 1/2^4 */
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module_param(dctcp_shift_g, uint, 0644);
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MODULE_PARM_DESC(dctcp_shift_g, "parameter g for updating dctcp_alpha");
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static unsigned int dctcp_alpha_on_init __read_mostly = DCTCP_MAX_ALPHA;
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module_param(dctcp_alpha_on_init, uint, 0644);
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MODULE_PARM_DESC(dctcp_alpha_on_init, "parameter for initial alpha value");
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static struct tcp_congestion_ops dctcp_reno;
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static void dctcp_reset(const struct tcp_sock *tp, struct dctcp *ca)
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{
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ca->next_seq = tp->snd_nxt;
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ca->old_delivered = tp->delivered;
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ca->old_delivered_ce = tp->delivered_ce;
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}
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__bpf_kfunc static void dctcp_init(struct sock *sk)
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{
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const struct tcp_sock *tp = tcp_sk(sk);
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if ((tp->ecn_flags & TCP_ECN_OK) ||
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(sk->sk_state == TCP_LISTEN ||
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sk->sk_state == TCP_CLOSE)) {
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struct dctcp *ca = inet_csk_ca(sk);
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ca->prior_rcv_nxt = tp->rcv_nxt;
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ca->dctcp_alpha = min(dctcp_alpha_on_init, DCTCP_MAX_ALPHA);
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ca->loss_cwnd = 0;
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ca->ce_state = 0;
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dctcp_reset(tp, ca);
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tcp_plb_init(sk, &ca->plb);
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return;
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}
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/* No ECN support? Fall back to Reno. Also need to clear
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* ECT from sk since it is set during 3WHS for DCTCP.
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*/
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inet_csk(sk)->icsk_ca_ops = &dctcp_reno;
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INET_ECN_dontxmit(sk);
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}
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__bpf_kfunc static u32 dctcp_ssthresh(struct sock *sk)
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{
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struct dctcp *ca = inet_csk_ca(sk);
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struct tcp_sock *tp = tcp_sk(sk);
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ca->loss_cwnd = tcp_snd_cwnd(tp);
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return max(tcp_snd_cwnd(tp) - ((tcp_snd_cwnd(tp) * ca->dctcp_alpha) >> 11U), 2U);
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}
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__bpf_kfunc static void dctcp_update_alpha(struct sock *sk, u32 flags)
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{
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const struct tcp_sock *tp = tcp_sk(sk);
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struct dctcp *ca = inet_csk_ca(sk);
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/* Expired RTT */
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if (!before(tp->snd_una, ca->next_seq)) {
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u32 delivered = tp->delivered - ca->old_delivered;
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u32 delivered_ce = tp->delivered_ce - ca->old_delivered_ce;
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u32 alpha = ca->dctcp_alpha;
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u32 ce_ratio = 0;
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if (delivered > 0) {
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/* dctcp_alpha keeps EWMA of fraction of ECN marked
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* packets. Because of EWMA smoothing, PLB reaction can
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* be slow so we use ce_ratio which is an instantaneous
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* measure of congestion. ce_ratio is the fraction of
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* ECN marked packets in the previous RTT.
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*/
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if (delivered_ce > 0)
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ce_ratio = (delivered_ce << TCP_PLB_SCALE) / delivered;
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tcp_plb_update_state(sk, &ca->plb, (int)ce_ratio);
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tcp_plb_check_rehash(sk, &ca->plb);
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}
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/* alpha = (1 - g) * alpha + g * F */
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alpha -= min_not_zero(alpha, alpha >> dctcp_shift_g);
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if (delivered_ce) {
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/* If dctcp_shift_g == 1, a 32bit value would overflow
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* after 8 M packets.
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*/
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delivered_ce <<= (10 - dctcp_shift_g);
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delivered_ce /= max(1U, delivered);
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alpha = min(alpha + delivered_ce, DCTCP_MAX_ALPHA);
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}
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/* dctcp_alpha can be read from dctcp_get_info() without
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* synchro, so we ask compiler to not use dctcp_alpha
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* as a temporary variable in prior operations.
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*/
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WRITE_ONCE(ca->dctcp_alpha, alpha);
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dctcp_reset(tp, ca);
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}
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}
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static void dctcp_react_to_loss(struct sock *sk)
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{
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struct dctcp *ca = inet_csk_ca(sk);
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struct tcp_sock *tp = tcp_sk(sk);
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ca->loss_cwnd = tcp_snd_cwnd(tp);
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tp->snd_ssthresh = max(tcp_snd_cwnd(tp) >> 1U, 2U);
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}
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__bpf_kfunc static void dctcp_state(struct sock *sk, u8 new_state)
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{
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if (new_state == TCP_CA_Recovery &&
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new_state != inet_csk(sk)->icsk_ca_state)
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dctcp_react_to_loss(sk);
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/* We handle RTO in dctcp_cwnd_event to ensure that we perform only
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* one loss-adjustment per RTT.
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*/
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}
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__bpf_kfunc static void dctcp_cwnd_event(struct sock *sk, enum tcp_ca_event ev)
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{
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struct dctcp *ca = inet_csk_ca(sk);
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switch (ev) {
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case CA_EVENT_ECN_IS_CE:
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case CA_EVENT_ECN_NO_CE:
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dctcp_ece_ack_update(sk, ev, &ca->prior_rcv_nxt, &ca->ce_state);
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break;
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case CA_EVENT_LOSS:
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tcp_plb_update_state_upon_rto(sk, &ca->plb);
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dctcp_react_to_loss(sk);
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break;
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case CA_EVENT_TX_START:
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tcp_plb_check_rehash(sk, &ca->plb); /* Maybe rehash when inflight is 0 */
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break;
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default:
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/* Don't care for the rest. */
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break;
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}
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}
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static size_t dctcp_get_info(struct sock *sk, u32 ext, int *attr,
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union tcp_cc_info *info)
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{
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const struct dctcp *ca = inet_csk_ca(sk);
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const struct tcp_sock *tp = tcp_sk(sk);
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/* Fill it also in case of VEGASINFO due to req struct limits.
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* We can still correctly retrieve it later.
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*/
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if (ext & (1 << (INET_DIAG_DCTCPINFO - 1)) ||
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ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
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memset(&info->dctcp, 0, sizeof(info->dctcp));
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if (inet_csk(sk)->icsk_ca_ops != &dctcp_reno) {
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info->dctcp.dctcp_enabled = 1;
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info->dctcp.dctcp_ce_state = (u16) ca->ce_state;
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info->dctcp.dctcp_alpha = ca->dctcp_alpha;
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info->dctcp.dctcp_ab_ecn = tp->mss_cache *
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(tp->delivered_ce - ca->old_delivered_ce);
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info->dctcp.dctcp_ab_tot = tp->mss_cache *
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(tp->delivered - ca->old_delivered);
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}
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*attr = INET_DIAG_DCTCPINFO;
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return sizeof(info->dctcp);
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}
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return 0;
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}
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__bpf_kfunc static u32 dctcp_cwnd_undo(struct sock *sk)
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{
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const struct dctcp *ca = inet_csk_ca(sk);
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struct tcp_sock *tp = tcp_sk(sk);
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return max(tcp_snd_cwnd(tp), ca->loss_cwnd);
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}
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static struct tcp_congestion_ops dctcp __read_mostly = {
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.init = dctcp_init,
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.in_ack_event = dctcp_update_alpha,
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.cwnd_event = dctcp_cwnd_event,
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.ssthresh = dctcp_ssthresh,
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.cong_avoid = tcp_reno_cong_avoid,
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.undo_cwnd = dctcp_cwnd_undo,
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.set_state = dctcp_state,
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.get_info = dctcp_get_info,
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.flags = TCP_CONG_NEEDS_ECN,
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.owner = THIS_MODULE,
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.name = "dctcp",
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};
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static struct tcp_congestion_ops dctcp_reno __read_mostly = {
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.ssthresh = tcp_reno_ssthresh,
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.cong_avoid = tcp_reno_cong_avoid,
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.undo_cwnd = tcp_reno_undo_cwnd,
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.get_info = dctcp_get_info,
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.owner = THIS_MODULE,
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.name = "dctcp-reno",
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};
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BTF_SET8_START(tcp_dctcp_check_kfunc_ids)
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#ifdef CONFIG_X86
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#ifdef CONFIG_DYNAMIC_FTRACE
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BTF_ID_FLAGS(func, dctcp_init)
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BTF_ID_FLAGS(func, dctcp_update_alpha)
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BTF_ID_FLAGS(func, dctcp_cwnd_event)
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BTF_ID_FLAGS(func, dctcp_ssthresh)
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BTF_ID_FLAGS(func, dctcp_cwnd_undo)
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BTF_ID_FLAGS(func, dctcp_state)
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#endif
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#endif
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BTF_SET8_END(tcp_dctcp_check_kfunc_ids)
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static const struct btf_kfunc_id_set tcp_dctcp_kfunc_set = {
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.owner = THIS_MODULE,
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.set = &tcp_dctcp_check_kfunc_ids,
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};
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static int __init dctcp_register(void)
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{
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int ret;
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BUILD_BUG_ON(sizeof(struct dctcp) > ICSK_CA_PRIV_SIZE);
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ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &tcp_dctcp_kfunc_set);
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if (ret < 0)
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return ret;
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return tcp_register_congestion_control(&dctcp);
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}
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static void __exit dctcp_unregister(void)
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{
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tcp_unregister_congestion_control(&dctcp);
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}
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module_init(dctcp_register);
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module_exit(dctcp_unregister);
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MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
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MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
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MODULE_AUTHOR("Glenn Judd <glenn.judd@morganstanley.com>");
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MODULE_LICENSE("GPL v2");
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MODULE_DESCRIPTION("DataCenter TCP (DCTCP)");
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