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Date: Wed, 28 Feb 2018 14:40:46 -0800
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Neal Cardwell <ncardwell@...gle.com>,
Yuchung Cheng <ycheng@...gle.com>,
Soheil Hassas Yeganeh <soheil@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 1/2] tcp_bbr: better deal with suboptimal GSO (II)
This is second part of dealing with suboptimal device gso parameters.
In first patch (350c9f484bde "tcp_bbr: better deal with suboptimal GSO")
we dealt with devices having low gso_max_segs
Some devices lower gso_max_size from 64KB to 16 KB (r8152 is an example)
In order to probe an optimal cwnd, we want BBR being not sensitive
to whatever GSO constraint a device can have.
This patch removes tso_segs_goal() CC callback in favor of
min_tso_segs() for CC wanting to override sysctl_tcp_min_tso_segs
Next patch will remove bbr->tso_segs_goal since it does not have
to be persistent.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/net/tcp.h | 6 ++----
net/ipv4/tcp_bbr.c | 23 +++++++++++++----------
net/ipv4/tcp_output.c | 15 ++++++++-------
3 files changed, 23 insertions(+), 21 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 92b06c6e7732ad7c61b580427fc085fa0dff1063..9c9b3768b350abfd51776563d220d5e97ca9da69 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -511,8 +511,6 @@ __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
#endif
/* tcp_output.c */
-u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
- int min_tso_segs);
void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
int nonagle);
int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs);
@@ -981,8 +979,8 @@ struct tcp_congestion_ops {
u32 (*undo_cwnd)(struct sock *sk);
/* hook for packet ack accounting (optional) */
void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample);
- /* suggest number of segments for each skb to transmit (optional) */
- u32 (*tso_segs_goal)(struct sock *sk);
+ /* override sysctl_tcp_min_tso_segs */
+ u32 (*min_tso_segs)(struct sock *sk);
/* returns the multiplier used in tcp_sndbuf_expand (optional) */
u32 (*sndbuf_expand)(struct sock *sk);
/* call when packets are delivered to update cwnd and pacing rate,
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
index a471f696e13c82cddd11633fd4bfdbc6d84f4bcc..afc0567b8a98fbb718ba04505053aa3f62ab5784 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -261,23 +261,26 @@ static void bbr_set_pacing_rate(struct sock *sk, u32 bw, int gain)
sk->sk_pacing_rate = rate;
}
-/* Return count of segments we want in the skbs we send, or 0 for default. */
-static u32 bbr_tso_segs_goal(struct sock *sk)
+/* override sysctl_tcp_min_tso_segs */
+static u32 bbr_min_tso_segs(struct sock *sk)
{
- struct bbr *bbr = inet_csk_ca(sk);
-
- return bbr->tso_segs_goal;
+ return sk->sk_pacing_rate < (bbr_min_tso_rate >> 3) ? 1 : 2;
}
static void bbr_set_tso_segs_goal(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
struct bbr *bbr = inet_csk_ca(sk);
- u32 min_segs;
+ u32 segs, bytes;
+
+ /* Sort of tcp_tso_autosize() but ignoring
+ * driver provided sk_gso_max_size.
+ */
+ bytes = min_t(u32, sk->sk_pacing_rate >> sk->sk_pacing_shift,
+ GSO_MAX_SIZE - 1 - MAX_TCP_HEADER);
+ segs = max_t(u32, bytes / tp->mss_cache, bbr_min_tso_segs(sk));
- min_segs = sk->sk_pacing_rate < (bbr_min_tso_rate >> 3) ? 1 : 2;
- bbr->tso_segs_goal = min(tcp_tso_autosize(sk, tp->mss_cache, min_segs),
- 0x7FU);
+ bbr->tso_segs_goal = min(segs, 0x7FU);
}
/* Save "last known good" cwnd so we can restore it after losses or PROBE_RTT */
@@ -936,7 +939,7 @@ static struct tcp_congestion_ops tcp_bbr_cong_ops __read_mostly = {
.undo_cwnd = bbr_undo_cwnd,
.cwnd_event = bbr_cwnd_event,
.ssthresh = bbr_ssthresh,
- .tso_segs_goal = bbr_tso_segs_goal,
+ .min_tso_segs = bbr_min_tso_segs,
.get_info = bbr_get_info,
.set_state = bbr_set_state,
};
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 49d043de3476bdfcaf6e9a606d0da0f2094373a8..383cac0ff0ec059ca7dbc1a6304cc7f8183e008d 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1703,8 +1703,8 @@ static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp,
/* Return how many segs we'd like on a TSO packet,
* to send one TSO packet per ms
*/
-u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
- int min_tso_segs)
+static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
+ int min_tso_segs)
{
u32 bytes, segs;
@@ -1720,7 +1720,6 @@ u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
return segs;
}
-EXPORT_SYMBOL(tcp_tso_autosize);
/* Return the number of segments we want in the skb we are transmitting.
* See if congestion control module wants to decide; otherwise, autosize.
@@ -1728,11 +1727,13 @@ EXPORT_SYMBOL(tcp_tso_autosize);
static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now)
{
const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
- u32 tso_segs = ca_ops->tso_segs_goal ? ca_ops->tso_segs_goal(sk) : 0;
+ u32 min_tso, tso_segs;
- if (!tso_segs)
- tso_segs = tcp_tso_autosize(sk, mss_now,
- sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs);
+ min_tso = ca_ops->min_tso_segs ?
+ ca_ops->min_tso_segs(sk) :
+ sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs;
+
+ tso_segs = tcp_tso_autosize(sk, mss_now, min_tso);
return min_t(u32, tso_segs, sk->sk_gso_max_segs);
}
--
2.16.2.395.g2e18187dfd-goog
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