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author | Eric Dumazet <edumazet@google.com> | 2019-04-11 05:55:23 -0700 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2019-04-11 21:31:03 -0700 |
commit | e3058450965972e67cc0e5492c08c4cdadafc134 (patch) | |
tree | 896df9274d78b1d868faef05ff1d6089c5b3bf85 /net | |
parent | a5f622984a623df9a84cf43f6b098d8dd76fbe05 (diff) | |
download | linux-e3058450965972e67cc0e5492c08c4cdadafc134.tar.gz linux-e3058450965972e67cc0e5492c08c4cdadafc134.tar.bz2 linux-e3058450965972e67cc0e5492c08c4cdadafc134.zip |
dctcp: more accurate tracking of packets delivery
After commit e21db6f69a95 ("tcp: track total bytes delivered with ECN CE marks")
core TCP stack does a very good job tracking ECN signals.
The "sender's best estimate of CE information" Yuchung mentioned in his
patch is indeed the best we can do.
DCTCP can use tp->delivered_ce and tp->delivered to not duplicate the logic,
and use the existing best estimate.
This solves some problems, since current DCTCP logic does not deal with losses
and/or GRO or ack aggregation very well.
This also removes a dubious use of inet_csk(sk)->icsk_ack.rcv_mss
(this should have been tp->mss_cache), and a 64 bit divide.
Finally, we can see that the DCTCP logic, calling dctcp_update_alpha() for
every ACK could be done differently, calling it only once per RTT.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Florian Westphal <fw@strlen.de>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Lawrence Brakmo <brakmo@fb.com>
Cc: Abdul Kabbani <akabbani@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r-- | net/ipv4/tcp_dctcp.c | 45 |
1 files changed, 17 insertions, 28 deletions
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c index 359da68d7c06..477cb4aa456c 100644 --- a/net/ipv4/tcp_dctcp.c +++ b/net/ipv4/tcp_dctcp.c @@ -49,9 +49,8 @@ #define DCTCP_MAX_ALPHA 1024U struct dctcp { - u32 acked_bytes_ecn; - u32 acked_bytes_total; - u32 prior_snd_una; + u32 old_delivered; + u32 old_delivered_ce; u32 prior_rcv_nxt; u32 dctcp_alpha; u32 next_seq; @@ -73,8 +72,8 @@ static void dctcp_reset(const struct tcp_sock *tp, struct dctcp *ca) { ca->next_seq = tp->snd_nxt; - ca->acked_bytes_ecn = 0; - ca->acked_bytes_total = 0; + ca->old_delivered = tp->delivered; + ca->old_delivered_ce = tp->delivered_ce; } static void dctcp_init(struct sock *sk) @@ -86,7 +85,6 @@ static void dctcp_init(struct sock *sk) sk->sk_state == TCP_CLOSE)) { struct dctcp *ca = inet_csk_ca(sk); - ca->prior_snd_una = tp->snd_una; ca->prior_rcv_nxt = tp->rcv_nxt; ca->dctcp_alpha = min(dctcp_alpha_on_init, DCTCP_MAX_ALPHA); @@ -118,37 +116,25 @@ static void dctcp_update_alpha(struct sock *sk, u32 flags) { const struct tcp_sock *tp = tcp_sk(sk); struct dctcp *ca = inet_csk_ca(sk); - u32 acked_bytes = tp->snd_una - ca->prior_snd_una; - - /* If ack did not advance snd_una, count dupack as MSS size. - * If ack did update window, do not count it at all. - */ - if (acked_bytes == 0 && !(flags & CA_ACK_WIN_UPDATE)) - acked_bytes = inet_csk(sk)->icsk_ack.rcv_mss; - if (acked_bytes) { - ca->acked_bytes_total += acked_bytes; - ca->prior_snd_una = tp->snd_una; - - if (flags & CA_ACK_ECE) - ca->acked_bytes_ecn += acked_bytes; - } /* Expired RTT */ if (!before(tp->snd_una, ca->next_seq)) { - u64 bytes_ecn = ca->acked_bytes_ecn; + u32 delivered_ce = tp->delivered_ce - ca->old_delivered_ce; u32 alpha = ca->dctcp_alpha; /* alpha = (1 - g) * alpha + g * F */ alpha -= min_not_zero(alpha, alpha >> dctcp_shift_g); - if (bytes_ecn) { + if (delivered_ce) { + u32 delivered = tp->delivered - ca->old_delivered; + /* If dctcp_shift_g == 1, a 32bit value would overflow - * after 8 Mbytes. + * after 8 M packets. */ - bytes_ecn <<= (10 - dctcp_shift_g); - do_div(bytes_ecn, max(1U, ca->acked_bytes_total)); + delivered_ce <<= (10 - dctcp_shift_g); + delivered_ce /= max(1U, delivered); - alpha = min(alpha + (u32)bytes_ecn, DCTCP_MAX_ALPHA); + alpha = min(alpha + delivered_ce, DCTCP_MAX_ALPHA); } /* dctcp_alpha can be read from dctcp_get_info() without * synchro, so we ask compiler to not use dctcp_alpha @@ -200,6 +186,7 @@ static size_t dctcp_get_info(struct sock *sk, u32 ext, int *attr, union tcp_cc_info *info) { const struct dctcp *ca = inet_csk_ca(sk); + const struct tcp_sock *tp = tcp_sk(sk); /* Fill it also in case of VEGASINFO due to req struct limits. * We can still correctly retrieve it later. @@ -211,8 +198,10 @@ static size_t dctcp_get_info(struct sock *sk, u32 ext, int *attr, info->dctcp.dctcp_enabled = 1; info->dctcp.dctcp_ce_state = (u16) ca->ce_state; info->dctcp.dctcp_alpha = ca->dctcp_alpha; - info->dctcp.dctcp_ab_ecn = ca->acked_bytes_ecn; - info->dctcp.dctcp_ab_tot = ca->acked_bytes_total; + info->dctcp.dctcp_ab_ecn = tp->mss_cache * + (tp->delivered_ce - ca->old_delivered_ce); + info->dctcp.dctcp_ab_tot = tp->mss_cache * + (tp->delivered - ca->old_delivered); } *attr = INET_DIAG_DCTCPINFO; |