mirror of https://gitee.com/openkylin/linux.git
bpf: tcp: Add bpf_cubic example
This patch adds a bpf_cubic example. Some highlights: 1. CONFIG_HZ .kconfig map is used. 2. In bictcp_update(), calculation is changed to use usec resolution (i.e. USEC_PER_JIFFY) instead of using jiffies. Thus, usecs_to_jiffies() is not used in the bpf_cubic.c. 3. In bitctcp_update() [under tcp_friendliness], the original "while (ca->ack_cnt > delta)" loop is changed to the equivalent "ca->ack_cnt / delta" operation. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200122233658.903774-1-kafai@fb.com
This commit is contained in:
Martin KaFai Lau
Alexei Starovoitov
parent
0a49c1a8e2
commit
6de4a9c430
|
|
@ -6,13 +6,28 @@
|
|||
#include <linux/types.h>
|
||||
#include <bpf/bpf_helpers.h>
|
||||
#include <bpf/bpf_core_read.h>
|
||||
#include "bpf_trace_helpers.h"
|
||||
|
||||
#define BPF_STRUCT_OPS(name, args...) \
|
||||
SEC("struct_ops/"#name) \
|
||||
BPF_PROG(name, args)
|
||||
|
||||
#define tcp_jiffies32 ((__u32)bpf_jiffies64())
|
||||
|
||||
struct sock_common {
|
||||
unsigned char skc_state;
|
||||
} __attribute__((preserve_access_index));
|
||||
|
||||
enum sk_pacing {
|
||||
SK_PACING_NONE = 0,
|
||||
SK_PACING_NEEDED = 1,
|
||||
SK_PACING_FQ = 2,
|
||||
};
|
||||
|
||||
struct sock {
|
||||
struct sock_common __sk_common;
|
||||
unsigned long sk_pacing_rate;
|
||||
__u32 sk_pacing_status; /* see enum sk_pacing */
|
||||
} __attribute__((preserve_access_index));
|
||||
|
||||
struct inet_sock {
|
||||
|
|
@ -54,6 +69,7 @@ struct tcp_sock {
|
|||
__u32 max_packets_out;
|
||||
__u32 lsndtime;
|
||||
__u32 prior_cwnd;
|
||||
__u64 tcp_mstamp; /* most recent packet received/sent */
|
||||
} __attribute__((preserve_access_index));
|
||||
|
||||
static __always_inline struct inet_connection_sock *inet_csk(const struct sock *sk)
|
||||
|
|
|
|||
|
|
@ -4,6 +4,7 @@
|
|||
#include <linux/err.h>
|
||||
#include <test_progs.h>
|
||||
#include "bpf_dctcp.skel.h"
|
||||
#include "bpf_cubic.skel.h"
|
||||
|
||||
#define min(a, b) ((a) < (b) ? (a) : (b))
|
||||
|
||||
|
|
@ -158,6 +159,28 @@ static void do_test(const char *tcp_ca)
|
|||
close(fd);
|
||||
}
|
||||
|
||||
static void test_cubic(void)
|
||||
{
|
||||
struct bpf_cubic *cubic_skel;
|
||||
struct bpf_link *link;
|
||||
|
||||
cubic_skel = bpf_cubic__open_and_load();
|
||||
if (CHECK(!cubic_skel, "bpf_cubic__open_and_load", "failed\n"))
|
||||
return;
|
||||
|
||||
link = bpf_map__attach_struct_ops(cubic_skel->maps.cubic);
|
||||
if (CHECK(IS_ERR(link), "bpf_map__attach_struct_ops", "err:%ld\n",
|
||||
PTR_ERR(link))) {
|
||||
bpf_cubic__destroy(cubic_skel);
|
||||
return;
|
||||
}
|
||||
|
||||
do_test("bpf_cubic");
|
||||
|
||||
bpf_link__destroy(link);
|
||||
bpf_cubic__destroy(cubic_skel);
|
||||
}
|
||||
|
||||
static void test_dctcp(void)
|
||||
{
|
||||
struct bpf_dctcp *dctcp_skel;
|
||||
|
|
@ -184,4 +207,6 @@ void test_bpf_tcp_ca(void)
|
|||
{
|
||||
if (test__start_subtest("dctcp"))
|
||||
test_dctcp();
|
||||
if (test__start_subtest("cubic"))
|
||||
test_cubic();
|
||||
}
|
||||
|
|
|
|||
|
|
@ -0,0 +1,544 @@
|
|||
// SPDX-License-Identifier: GPL-2.0-only
|
||||
|
||||
/* WARNING: This implemenation is not necessarily the same
|
||||
* as the tcp_cubic.c. The purpose is mainly for testing
|
||||
* the kernel BPF logic.
|
||||
*
|
||||
* Highlights:
|
||||
* 1. CONFIG_HZ .kconfig map is used.
|
||||
* 2. In bictcp_update(), calculation is changed to use usec
|
||||
* resolution (i.e. USEC_PER_JIFFY) instead of using jiffies.
|
||||
* Thus, usecs_to_jiffies() is not used in the bpf_cubic.c.
|
||||
* 3. In bitctcp_update() [under tcp_friendliness], the original
|
||||
* "while (ca->ack_cnt > delta)" loop is changed to the equivalent
|
||||
* "ca->ack_cnt / delta" operation.
|
||||
*/
|
||||
|
||||
#include <linux/bpf.h>
|
||||
#include "bpf_tcp_helpers.h"
|
||||
|
||||
char _license[] SEC("license") = "GPL";
|
||||
|
||||
#define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
|
||||
|
||||
#define BICTCP_BETA_SCALE 1024 /* Scale factor beta calculation
|
||||
* max_cwnd = snd_cwnd * beta
|
||||
*/
|
||||
#define BICTCP_HZ 10 /* BIC HZ 2^10 = 1024 */
|
||||
|
||||
/* Two methods of hybrid slow start */
|
||||
#define HYSTART_ACK_TRAIN 0x1
|
||||
#define HYSTART_DELAY 0x2
|
||||
|
||||
/* Number of delay samples for detecting the increase of delay */
|
||||
#define HYSTART_MIN_SAMPLES 8
|
||||
#define HYSTART_DELAY_MIN (4000U) /* 4ms */
|
||||
#define HYSTART_DELAY_MAX (16000U) /* 16 ms */
|
||||
#define HYSTART_DELAY_THRESH(x) clamp(x, HYSTART_DELAY_MIN, HYSTART_DELAY_MAX)
|
||||
|
||||
static int fast_convergence = 1;
|
||||
static const int beta = 717; /* = 717/1024 (BICTCP_BETA_SCALE) */
|
||||
static int initial_ssthresh;
|
||||
static const int bic_scale = 41;
|
||||
static int tcp_friendliness = 1;
|
||||
|
||||
static int hystart = 1;
|
||||
static int hystart_detect = HYSTART_ACK_TRAIN | HYSTART_DELAY;
|
||||
static int hystart_low_window = 16;
|
||||
static int hystart_ack_delta_us = 2000;
|
||||
|
||||
static const __u32 cube_rtt_scale = (bic_scale * 10); /* 1024*c/rtt */
|
||||
static const __u32 beta_scale = 8*(BICTCP_BETA_SCALE+beta) / 3
|
||||
/ (BICTCP_BETA_SCALE - beta);
|
||||
/* calculate the "K" for (wmax-cwnd) = c/rtt * K^3
|
||||
* so K = cubic_root( (wmax-cwnd)*rtt/c )
|
||||
* the unit of K is bictcp_HZ=2^10, not HZ
|
||||
*
|
||||
* c = bic_scale >> 10
|
||||
* rtt = 100ms
|
||||
*
|
||||
* the following code has been designed and tested for
|
||||
* cwnd < 1 million packets
|
||||
* RTT < 100 seconds
|
||||
* HZ < 1,000,00 (corresponding to 10 nano-second)
|
||||
*/
|
||||
|
||||
/* 1/c * 2^2*bictcp_HZ * srtt, 2^40 */
|
||||
static const __u64 cube_factor = (__u64)(1ull << (10+3*BICTCP_HZ))
|
||||
/ (bic_scale * 10);
|
||||
|
||||
/* BIC TCP Parameters */
|
||||
struct bictcp {
|
||||
__u32 cnt; /* increase cwnd by 1 after ACKs */
|
||||
__u32 last_max_cwnd; /* last maximum snd_cwnd */
|
||||
__u32 last_cwnd; /* the last snd_cwnd */
|
||||
__u32 last_time; /* time when updated last_cwnd */
|
||||
__u32 bic_origin_point;/* origin point of bic function */
|
||||
__u32 bic_K; /* time to origin point
|
||||
from the beginning of the current epoch */
|
||||
__u32 delay_min; /* min delay (usec) */
|
||||
__u32 epoch_start; /* beginning of an epoch */
|
||||
__u32 ack_cnt; /* number of acks */
|
||||
__u32 tcp_cwnd; /* estimated tcp cwnd */
|
||||
__u16 unused;
|
||||
__u8 sample_cnt; /* number of samples to decide curr_rtt */
|
||||
__u8 found; /* the exit point is found? */
|
||||
__u32 round_start; /* beginning of each round */
|
||||
__u32 end_seq; /* end_seq of the round */
|
||||
__u32 last_ack; /* last time when the ACK spacing is close */
|
||||
__u32 curr_rtt; /* the minimum rtt of current round */
|
||||
};
|
||||
|
||||
static inline void bictcp_reset(struct bictcp *ca)
|
||||
{
|
||||
ca->cnt = 0;
|
||||
ca->last_max_cwnd = 0;
|
||||
ca->last_cwnd = 0;
|
||||
ca->last_time = 0;
|
||||
ca->bic_origin_point = 0;
|
||||
ca->bic_K = 0;
|
||||
ca->delay_min = 0;
|
||||
ca->epoch_start = 0;
|
||||
ca->ack_cnt = 0;
|
||||
ca->tcp_cwnd = 0;
|
||||
ca->found = 0;
|
||||
}
|
||||
|
||||
extern unsigned long CONFIG_HZ __kconfig;
|
||||
#define HZ CONFIG_HZ
|
||||
#define USEC_PER_MSEC 1000UL
|
||||
#define USEC_PER_SEC 1000000UL
|
||||
#define USEC_PER_JIFFY (USEC_PER_SEC / HZ)
|
||||
|
||||
static __always_inline __u64 div64_u64(__u64 dividend, __u64 divisor)
|
||||
{
|
||||
return dividend / divisor;
|
||||
}
|
||||
|
||||
#define div64_ul div64_u64
|
||||
|
||||
#define BITS_PER_U64 (sizeof(__u64) * 8)
|
||||
static __always_inline int fls64(__u64 x)
|
||||
{
|
||||
int num = BITS_PER_U64 - 1;
|
||||
|
||||
if (x == 0)
|
||||
return 0;
|
||||
|
||||
if (!(x & (~0ull << (BITS_PER_U64-32)))) {
|
||||
num -= 32;
|
||||
x <<= 32;
|
||||
}
|
||||
if (!(x & (~0ull << (BITS_PER_U64-16)))) {
|
||||
num -= 16;
|
||||
x <<= 16;
|
||||
}
|
||||
if (!(x & (~0ull << (BITS_PER_U64-8)))) {
|
||||
num -= 8;
|
||||
x <<= 8;
|
||||
}
|
||||
if (!(x & (~0ull << (BITS_PER_U64-4)))) {
|
||||
num -= 4;
|
||||
x <<= 4;
|
||||
}
|
||||
if (!(x & (~0ull << (BITS_PER_U64-2)))) {
|
||||
num -= 2;
|
||||
x <<= 2;
|
||||
}
|
||||
if (!(x & (~0ull << (BITS_PER_U64-1))))
|
||||
num -= 1;
|
||||
|
||||
return num + 1;
|
||||
}
|
||||
|
||||
static __always_inline __u32 bictcp_clock_us(const struct sock *sk)
|
||||
{
|
||||
return tcp_sk(sk)->tcp_mstamp;
|
||||
}
|
||||
|
||||
static __always_inline void bictcp_hystart_reset(struct sock *sk)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
struct bictcp *ca = inet_csk_ca(sk);
|
||||
|
||||
ca->round_start = ca->last_ack = bictcp_clock_us(sk);
|
||||
ca->end_seq = tp->snd_nxt;
|
||||
ca->curr_rtt = ~0U;
|
||||
ca->sample_cnt = 0;
|
||||
}
|
||||
|
||||
/* "struct_ops/" prefix is not a requirement
|
||||
* It will be recognized as BPF_PROG_TYPE_STRUCT_OPS
|
||||
* as long as it is used in one of the func ptr
|
||||
* under SEC(".struct_ops").
|
||||
*/
|
||||
SEC("struct_ops/bictcp_init")
|
||||
void BPF_PROG(bictcp_init, struct sock *sk)
|
||||
{
|
||||
struct bictcp *ca = inet_csk_ca(sk);
|
||||
|
||||
bictcp_reset(ca);
|
||||
|
||||
if (hystart)
|
||||
bictcp_hystart_reset(sk);
|
||||
|
||||
if (!hystart && initial_ssthresh)
|
||||
tcp_sk(sk)->snd_ssthresh = initial_ssthresh;
|
||||
}
|
||||
|
||||
/* No prefix in SEC will also work.
|
||||
* The remaining tcp-cubic functions have an easier way.
|
||||
*/
|
||||
SEC("no-sec-prefix-bictcp_cwnd_event")
|
||||
void BPF_PROG(bictcp_cwnd_event, struct sock *sk, enum tcp_ca_event event)
|
||||
{
|
||||
if (event == CA_EVENT_TX_START) {
|
||||
struct bictcp *ca = inet_csk_ca(sk);
|
||||
__u32 now = tcp_jiffies32;
|
||||
__s32 delta;
|
||||
|
||||
delta = now - tcp_sk(sk)->lsndtime;
|
||||
|
||||
/* We were application limited (idle) for a while.
|
||||
* Shift epoch_start to keep cwnd growth to cubic curve.
|
||||
*/
|
||||
if (ca->epoch_start && delta > 0) {
|
||||
ca->epoch_start += delta;
|
||||
if (after(ca->epoch_start, now))
|
||||
ca->epoch_start = now;
|
||||
}
|
||||
return;
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* cbrt(x) MSB values for x MSB values in [0..63].
|
||||
* Precomputed then refined by hand - Willy Tarreau
|
||||
*
|
||||
* For x in [0..63],
|
||||
* v = cbrt(x << 18) - 1
|
||||
* cbrt(x) = (v[x] + 10) >> 6
|
||||
*/
|
||||
static const __u8 v[] = {
|
||||
/* 0x00 */ 0, 54, 54, 54, 118, 118, 118, 118,
|
||||
/* 0x08 */ 123, 129, 134, 138, 143, 147, 151, 156,
|
||||
/* 0x10 */ 157, 161, 164, 168, 170, 173, 176, 179,
|
||||
/* 0x18 */ 181, 185, 187, 190, 192, 194, 197, 199,
|
||||
/* 0x20 */ 200, 202, 204, 206, 209, 211, 213, 215,
|
||||
/* 0x28 */ 217, 219, 221, 222, 224, 225, 227, 229,
|
||||
/* 0x30 */ 231, 232, 234, 236, 237, 239, 240, 242,
|
||||
/* 0x38 */ 244, 245, 246, 248, 250, 251, 252, 254,
|
||||
};
|
||||
|
||||
/* calculate the cubic root of x using a table lookup followed by one
|
||||
* Newton-Raphson iteration.
|
||||
* Avg err ~= 0.195%
|
||||
*/
|
||||
static __always_inline __u32 cubic_root(__u64 a)
|
||||
{
|
||||
__u32 x, b, shift;
|
||||
|
||||
if (a < 64) {
|
||||
/* a in [0..63] */
|
||||
return ((__u32)v[(__u32)a] + 35) >> 6;
|
||||
}
|
||||
|
||||
b = fls64(a);
|
||||
b = ((b * 84) >> 8) - 1;
|
||||
shift = (a >> (b * 3));
|
||||
|
||||
/* it is needed for verifier's bound check on v */
|
||||
if (shift >= 64)
|
||||
return 0;
|
||||
|
||||
x = ((__u32)(((__u32)v[shift] + 10) << b)) >> 6;
|
||||
|
||||
/*
|
||||
* Newton-Raphson iteration
|
||||
* 2
|
||||
* x = ( 2 * x + a / x ) / 3
|
||||
* k+1 k k
|
||||
*/
|
||||
x = (2 * x + (__u32)div64_u64(a, (__u64)x * (__u64)(x - 1)));
|
||||
x = ((x * 341) >> 10);
|
||||
return x;
|
||||
}
|
||||
|
||||
/*
|
||||
* Compute congestion window to use.
|
||||
*/
|
||||
static __always_inline void bictcp_update(struct bictcp *ca, __u32 cwnd,
|
||||
__u32 acked)
|
||||
{
|
||||
__u32 delta, bic_target, max_cnt;
|
||||
__u64 offs, t;
|
||||
|
||||
ca->ack_cnt += acked; /* count the number of ACKed packets */
|
||||
|
||||
if (ca->last_cwnd == cwnd &&
|
||||
(__s32)(tcp_jiffies32 - ca->last_time) <= HZ / 32)
|
||||
return;
|
||||
|
||||
/* The CUBIC function can update ca->cnt at most once per jiffy.
|
||||
* On all cwnd reduction events, ca->epoch_start is set to 0,
|
||||
* which will force a recalculation of ca->cnt.
|
||||
*/
|
||||
if (ca->epoch_start && tcp_jiffies32 == ca->last_time)
|
||||
goto tcp_friendliness;
|
||||
|
||||
ca->last_cwnd = cwnd;
|
||||
ca->last_time = tcp_jiffies32;
|
||||
|
||||
if (ca->epoch_start == 0) {
|
||||
ca->epoch_start = tcp_jiffies32; /* record beginning */
|
||||
ca->ack_cnt = acked; /* start counting */
|
||||
ca->tcp_cwnd = cwnd; /* syn with cubic */
|
||||
|
||||
if (ca->last_max_cwnd <= cwnd) {
|
||||
ca->bic_K = 0;
|
||||
ca->bic_origin_point = cwnd;
|
||||
} else {
|
||||
/* Compute new K based on
|
||||
* (wmax-cwnd) * (srtt>>3 / HZ) / c * 2^(3*bictcp_HZ)
|
||||
*/
|
||||
ca->bic_K = cubic_root(cube_factor
|
||||
* (ca->last_max_cwnd - cwnd));
|
||||
ca->bic_origin_point = ca->last_max_cwnd;
|
||||
}
|
||||
}
|
||||
|
||||
/* cubic function - calc*/
|
||||
/* calculate c * time^3 / rtt,
|
||||
* while considering overflow in calculation of time^3
|
||||
* (so time^3 is done by using 64 bit)
|
||||
* and without the support of division of 64bit numbers
|
||||
* (so all divisions are done by using 32 bit)
|
||||
* also NOTE the unit of those veriables
|
||||
* time = (t - K) / 2^bictcp_HZ
|
||||
* c = bic_scale >> 10
|
||||
* rtt = (srtt >> 3) / HZ
|
||||
* !!! The following code does not have overflow problems,
|
||||
* if the cwnd < 1 million packets !!!
|
||||
*/
|
||||
|
||||
t = (__s32)(tcp_jiffies32 - ca->epoch_start) * USEC_PER_JIFFY;
|
||||
t += ca->delay_min;
|
||||
/* change the unit from usec to bictcp_HZ */
|
||||
t <<= BICTCP_HZ;
|
||||
t /= USEC_PER_SEC;
|
||||
|
||||
if (t < ca->bic_K) /* t - K */
|
||||
offs = ca->bic_K - t;
|
||||
else
|
||||
offs = t - ca->bic_K;
|
||||
|
||||
/* c/rtt * (t-K)^3 */
|
||||
delta = (cube_rtt_scale * offs * offs * offs) >> (10+3*BICTCP_HZ);
|
||||
if (t < ca->bic_K) /* below origin*/
|
||||
bic_target = ca->bic_origin_point - delta;
|
||||
else /* above origin*/
|
||||
bic_target = ca->bic_origin_point + delta;
|
||||
|
||||
/* cubic function - calc bictcp_cnt*/
|
||||
if (bic_target > cwnd) {
|
||||
ca->cnt = cwnd / (bic_target - cwnd);
|
||||
} else {
|
||||
ca->cnt = 100 * cwnd; /* very small increment*/
|
||||
}
|
||||
|
||||
/*
|
||||
* The initial growth of cubic function may be too conservative
|
||||
* when the available bandwidth is still unknown.
|
||||
*/
|
||||
if (ca->last_max_cwnd == 0 && ca->cnt > 20)
|
||||
ca->cnt = 20; /* increase cwnd 5% per RTT */
|
||||
|
||||
tcp_friendliness:
|
||||
/* TCP Friendly */
|
||||
if (tcp_friendliness) {
|
||||
__u32 scale = beta_scale;
|
||||
__u32 n;
|
||||
|
||||
/* update tcp cwnd */
|
||||
delta = (cwnd * scale) >> 3;
|
||||
if (ca->ack_cnt > delta && delta) {
|
||||
n = ca->ack_cnt / delta;
|
||||
ca->ack_cnt -= n * delta;
|
||||
ca->tcp_cwnd += n;
|
||||
}
|
||||
|
||||
if (ca->tcp_cwnd > cwnd) { /* if bic is slower than tcp */
|
||||
delta = ca->tcp_cwnd - cwnd;
|
||||
max_cnt = cwnd / delta;
|
||||
if (ca->cnt > max_cnt)
|
||||
ca->cnt = max_cnt;
|
||||
}
|
||||
}
|
||||
|
||||
/* The maximum rate of cwnd increase CUBIC allows is 1 packet per
|
||||
* 2 packets ACKed, meaning cwnd grows at 1.5x per RTT.
|
||||
*/
|
||||
ca->cnt = max(ca->cnt, 2U);
|
||||
}
|
||||
|
||||
/* Or simply use the BPF_STRUCT_OPS to avoid the SEC boiler plate. */
|
||||
void BPF_STRUCT_OPS(bictcp_cong_avoid, struct sock *sk, __u32 ack, __u32 acked)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
struct bictcp *ca = inet_csk_ca(sk);
|
||||
|
||||
if (!tcp_is_cwnd_limited(sk))
|
||||
return;
|
||||
|
||||
if (tcp_in_slow_start(tp)) {
|
||||
if (hystart && after(ack, ca->end_seq))
|
||||
bictcp_hystart_reset(sk);
|
||||
acked = tcp_slow_start(tp, acked);
|
||||
if (!acked)
|
||||
return;
|
||||
}
|
||||
bictcp_update(ca, tp->snd_cwnd, acked);
|
||||
tcp_cong_avoid_ai(tp, ca->cnt, acked);
|
||||
}
|
||||
|
||||
__u32 BPF_STRUCT_OPS(bictcp_recalc_ssthresh, struct sock *sk)
|
||||
{
|
||||
const struct tcp_sock *tp = tcp_sk(sk);
|
||||
struct bictcp *ca = inet_csk_ca(sk);
|
||||
|
||||
ca->epoch_start = 0; /* end of epoch */
|
||||
|
||||
/* Wmax and fast convergence */
|
||||
if (tp->snd_cwnd < ca->last_max_cwnd && fast_convergence)
|
||||
ca->last_max_cwnd = (tp->snd_cwnd * (BICTCP_BETA_SCALE + beta))
|
||||
/ (2 * BICTCP_BETA_SCALE);
|
||||
else
|
||||
ca->last_max_cwnd = tp->snd_cwnd;
|
||||
|
||||
return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);
|
||||
}
|
||||
|
||||
void BPF_STRUCT_OPS(bictcp_state, struct sock *sk, __u8 new_state)
|
||||
{
|
||||
if (new_state == TCP_CA_Loss) {
|
||||
bictcp_reset(inet_csk_ca(sk));
|
||||
bictcp_hystart_reset(sk);
|
||||
}
|
||||
}
|
||||
|
||||
#define GSO_MAX_SIZE 65536
|
||||
|
||||
/* Account for TSO/GRO delays.
|
||||
* Otherwise short RTT flows could get too small ssthresh, since during
|
||||
* slow start we begin with small TSO packets and ca->delay_min would
|
||||
* not account for long aggregation delay when TSO packets get bigger.
|
||||
* Ideally even with a very small RTT we would like to have at least one
|
||||
* TSO packet being sent and received by GRO, and another one in qdisc layer.
|
||||
* We apply another 100% factor because @rate is doubled at this point.
|
||||
* We cap the cushion to 1ms.
|
||||
*/
|
||||
static __always_inline __u32 hystart_ack_delay(struct sock *sk)
|
||||
{
|
||||
unsigned long rate;
|
||||
|
||||
rate = sk->sk_pacing_rate;
|
||||
if (!rate)
|
||||
return 0;
|
||||
return min((__u64)USEC_PER_MSEC,
|
||||
div64_ul((__u64)GSO_MAX_SIZE * 4 * USEC_PER_SEC, rate));
|
||||
}
|
||||
|
||||
static __always_inline void hystart_update(struct sock *sk, __u32 delay)
|
||||
{
|
||||
struct tcp_sock *tp = tcp_sk(sk);
|
||||
struct bictcp *ca = inet_csk_ca(sk);
|
||||
__u32 threshold;
|
||||
|
||||
if (hystart_detect & HYSTART_ACK_TRAIN) {
|
||||
__u32 now = bictcp_clock_us(sk);
|
||||
|
||||
/* first detection parameter - ack-train detection */
|
||||
if ((__s32)(now - ca->last_ack) <= hystart_ack_delta_us) {
|
||||
ca->last_ack = now;
|
||||
|
||||
threshold = ca->delay_min + hystart_ack_delay(sk);
|
||||
|
||||
/* Hystart ack train triggers if we get ack past
|
||||
* ca->delay_min/2.
|
||||
* Pacing might have delayed packets up to RTT/2
|
||||
* during slow start.
|
||||
*/
|
||||
if (sk->sk_pacing_status == SK_PACING_NONE)
|
||||
threshold >>= 1;
|
||||
|
||||
if ((__s32)(now - ca->round_start) > threshold) {
|
||||
ca->found = 1;
|
||||
tp->snd_ssthresh = tp->snd_cwnd;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
if (hystart_detect & HYSTART_DELAY) {
|
||||
/* obtain the minimum delay of more than sampling packets */
|
||||
if (ca->sample_cnt < HYSTART_MIN_SAMPLES) {
|
||||
if (ca->curr_rtt > delay)
|
||||
ca->curr_rtt = delay;
|
||||
|
||||
ca->sample_cnt++;
|
||||
} else {
|
||||
if (ca->curr_rtt > ca->delay_min +
|
||||
HYSTART_DELAY_THRESH(ca->delay_min >> 3)) {
|
||||
ca->found = 1;
|
||||
tp->snd_ssthresh = tp->snd_cwnd;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
void BPF_STRUCT_OPS(bictcp_acked, struct sock *sk,
|
||||
const struct ack_sample *sample)
|
||||
{
|
||||
const struct tcp_sock *tp = tcp_sk(sk);
|
||||
struct bictcp *ca = inet_csk_ca(sk);
|
||||
__u32 delay;
|
||||
|
||||
/* Some calls are for duplicates without timetamps */
|
||||
if (sample->rtt_us < 0)
|
||||
return;
|
||||
|
||||
/* Discard delay samples right after fast recovery */
|
||||
if (ca->epoch_start && (__s32)(tcp_jiffies32 - ca->epoch_start) < HZ)
|
||||
return;
|
||||
|
||||
delay = sample->rtt_us;
|
||||
if (delay == 0)
|
||||
delay = 1;
|
||||
|
||||
/* first time call or link delay decreases */
|
||||
if (ca->delay_min == 0 || ca->delay_min > delay)
|
||||
ca->delay_min = delay;
|
||||
|
||||
/* hystart triggers when cwnd is larger than some threshold */
|
||||
if (!ca->found && tcp_in_slow_start(tp) && hystart &&
|
||||
tp->snd_cwnd >= hystart_low_window)
|
||||
hystart_update(sk, delay);
|
||||
}
|
||||
|
||||
__u32 BPF_STRUCT_OPS(tcp_reno_undo_cwnd, struct sock *sk)
|
||||
{
|
||||
const struct tcp_sock *tp = tcp_sk(sk);
|
||||
|
||||
return max(tp->snd_cwnd, tp->prior_cwnd);
|
||||
}
|
||||
|
||||
SEC(".struct_ops")
|
||||
struct tcp_congestion_ops cubic = {
|
||||
.init = (void *)bictcp_init,
|
||||
.ssthresh = (void *)bictcp_recalc_ssthresh,
|
||||
.cong_avoid = (void *)bictcp_cong_avoid,
|
||||
.set_state = (void *)bictcp_state,
|
||||
.undo_cwnd = (void *)tcp_reno_undo_cwnd,
|
||||
.cwnd_event = (void *)bictcp_cwnd_event,
|
||||
.pkts_acked = (void *)bictcp_acked,
|
||||
.name = "bpf_cubic",
|
||||
};
|
||||
Loading…
Reference in New Issue