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Diffstat (limited to 'net/ipv4/tcp_cubic.c')
-rw-r--r--net/ipv4/tcp_cubic.c83
1 files changed, 54 insertions, 29 deletions
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 1b3d032a4df2..8f8eefd3a3ce 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -40,8 +40,8 @@
/* Number of delay samples for detecting the increase of delay */
#define HYSTART_MIN_SAMPLES 8
-#define HYSTART_DELAY_MIN (4U<<3)
-#define HYSTART_DELAY_MAX (16U<<3)
+#define HYSTART_DELAY_MIN (4000U) /* 4 ms */
+#define HYSTART_DELAY_MAX (16000U) /* 16 ms */
#define HYSTART_DELAY_THRESH(x) clamp(x, HYSTART_DELAY_MIN, HYSTART_DELAY_MAX)
static int fast_convergence __read_mostly = 1;
@@ -53,7 +53,7 @@ static int tcp_friendliness __read_mostly = 1;
static int hystart __read_mostly = 1;
static int hystart_detect __read_mostly = HYSTART_ACK_TRAIN | HYSTART_DELAY;
static int hystart_low_window __read_mostly = 16;
-static int hystart_ack_delta __read_mostly = 2;
+static int hystart_ack_delta_us __read_mostly = 2000;
static u32 cube_rtt_scale __read_mostly;
static u32 beta_scale __read_mostly;
@@ -77,8 +77,8 @@ MODULE_PARM_DESC(hystart_detect, "hybrid slow start detection mechanisms"
" 1: packet-train 2: delay 3: both packet-train and delay");
module_param(hystart_low_window, int, 0644);
MODULE_PARM_DESC(hystart_low_window, "lower bound cwnd for hybrid slow start");
-module_param(hystart_ack_delta, int, 0644);
-MODULE_PARM_DESC(hystart_ack_delta, "spacing between ack's indicating train (msecs)");
+module_param(hystart_ack_delta_us, int, 0644);
+MODULE_PARM_DESC(hystart_ack_delta_us, "spacing between ack's indicating train (usecs)");
/* BIC TCP Parameters */
struct bictcp {
@@ -89,7 +89,7 @@ struct bictcp {
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 (msec << 3) */
+ 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 */
@@ -117,13 +117,9 @@ static inline void bictcp_reset(struct bictcp *ca)
ca->found = 0;
}
-static inline u32 bictcp_clock(void)
+static inline u32 bictcp_clock_us(const struct sock *sk)
{
-#if HZ < 1000
- return ktime_to_ms(ktime_get_real());
-#else
- return jiffies_to_msecs(jiffies);
-#endif
+ return tcp_sk(sk)->tcp_mstamp;
}
static inline void bictcp_hystart_reset(struct sock *sk)
@@ -131,9 +127,9 @@ static 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();
+ ca->round_start = ca->last_ack = bictcp_clock_us(sk);
ca->end_seq = tp->snd_nxt;
- ca->curr_rtt = 0;
+ ca->curr_rtt = ~0U;
ca->sample_cnt = 0;
}
@@ -276,7 +272,7 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd, u32 acked)
*/
t = (s32)(tcp_jiffies32 - ca->epoch_start);
- t += msecs_to_jiffies(ca->delay_min >> 3);
+ t += usecs_to_jiffies(ca->delay_min);
/* change the unit from HZ to bictcp_HZ */
t <<= BICTCP_HZ;
do_div(t, HZ);
@@ -376,22 +372,54 @@ static void bictcp_state(struct sock *sk, u8 new_state)
}
}
+/* 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 u32 hystart_ack_delay(struct sock *sk)
+{
+ unsigned long rate;
+
+ rate = READ_ONCE(sk->sk_pacing_rate);
+ if (!rate)
+ return 0;
+ return min_t(u64, USEC_PER_MSEC,
+ div64_ul((u64)GSO_MAX_SIZE * 4 * USEC_PER_SEC, rate));
+}
+
static void hystart_update(struct sock *sk, u32 delay)
{
struct tcp_sock *tp = tcp_sk(sk);
struct bictcp *ca = inet_csk_ca(sk);
-
- if (ca->found & hystart_detect)
- return;
+ u32 threshold;
if (hystart_detect & HYSTART_ACK_TRAIN) {
- u32 now = bictcp_clock();
+ u32 now = bictcp_clock_us(sk);
/* first detection parameter - ack-train detection */
- if ((s32)(now - ca->last_ack) <= hystart_ack_delta) {
+ if ((s32)(now - ca->last_ack) <= hystart_ack_delta_us) {
ca->last_ack = now;
- if ((s32)(now - ca->round_start) > ca->delay_min >> 4) {
- ca->found |= HYSTART_ACK_TRAIN;
+
+ 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;
+ pr_debug("hystart_ack_train (%u > %u) delay_min %u (+ ack_delay %u) cwnd %u\n",
+ now - ca->round_start, threshold,
+ ca->delay_min, hystart_ack_delay(sk), tp->snd_cwnd);
NET_INC_STATS(sock_net(sk),
LINUX_MIB_TCPHYSTARTTRAINDETECT);
NET_ADD_STATS(sock_net(sk),
@@ -405,14 +433,14 @@ static void hystart_update(struct sock *sk, u32 delay)
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 == 0 || ca->curr_rtt > delay)
+ 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 |= HYSTART_DELAY;
+ ca->found = 1;
NET_INC_STATS(sock_net(sk),
LINUX_MIB_TCPHYSTARTDELAYDETECT);
NET_ADD_STATS(sock_net(sk),
@@ -424,9 +452,6 @@ static void hystart_update(struct sock *sk, u32 delay)
}
}
-/* Track delayed acknowledgment ratio using sliding window
- * ratio = (15*ratio + sample) / 16
- */
static void bictcp_acked(struct sock *sk, const struct ack_sample *sample)
{
const struct tcp_sock *tp = tcp_sk(sk);
@@ -441,7 +466,7 @@ static void bictcp_acked(struct sock *sk, const struct ack_sample *sample)
if (ca->epoch_start && (s32)(tcp_jiffies32 - ca->epoch_start) < HZ)
return;
- delay = (sample->rtt_us << 3) / USEC_PER_MSEC;
+ delay = sample->rtt_us;
if (delay == 0)
delay = 1;
@@ -450,7 +475,7 @@ static void bictcp_acked(struct sock *sk, const struct ack_sample *sample)
ca->delay_min = delay;
/* hystart triggers when cwnd is larger than some threshold */
- if (hystart && tcp_in_slow_start(tp) &&
+ if (!ca->found && tcp_in_slow_start(tp) && hystart &&
tp->snd_cwnd >= hystart_low_window)
hystart_update(sk, delay);
}
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