diff options
| -rw-r--r-- | tcp.c | 38 |
1 files changed, 38 insertions, 0 deletions
@@ -353,6 +353,13 @@ enum { #define LOW_RTT_TABLE_SIZE 8 #define LOW_RTT_THRESHOLD 10 /* us */ +/* Parameters to temporarily exceed sending buffer to force TCP auto-tuning */ +#define SNDBUF_BOOST_BYTES_RTT_LO 2500 /* B * s: no boost until here */ +/* ...examples: 5 MB sent * 500 ns RTT, 250 kB * 10 ms, 8 kB * 300 ms */ +#define SNDBUF_BOOST_FACTOR 150 /* % */ +#define SNDBUF_BOOST_BYTES_RTT_HI 6000 /* apply full boost factor */ +/* 12 MB sent * 500 ns RTT, 600 kB * 10 ms, 20 kB * 300 ms */ + /* Ratio of buffer to bandwidth * delay product implying interactive traffic */ #define SNDBUF_TO_BW_DELAY_INTERACTIVE /* > */ 20 /* (i.e. < 5% of buffer) */ @@ -1037,6 +1044,35 @@ void tcp_fill_headers(const struct ctx *c, struct tcp_tap_conn *conn, } /** + * tcp_sndbuf_boost() - Calculate limit of sending buffer to force auto-tuning + * @conn: Connection pointer + * @tinfo: tcp_info from kernel, must be pre-fetched + * + * Return: increased sending buffer to use as a limit for advertised window + */ +static unsigned long tcp_sndbuf_boost(const struct tcp_tap_conn *conn, + const struct tcp_info_linux *tinfo) +{ + unsigned long bytes_rtt_product; + + if (!bytes_acked_cap) + return SNDBUF_GET(conn); + + /* This is *not* a bandwidth-delay product, but it's somewhat related: + * as we send more data (usually at the beginning of a connection), we + * try to make the sending buffer progressively grow, with the RTT as a + * factor (longer delay, bigger buffer needed). + */ + bytes_rtt_product = (long long)tinfo->tcpi_bytes_acked * + tinfo->tcpi_rtt / 1000 / 1000; + + return clamped_scale(SNDBUF_GET(conn), bytes_rtt_product, + SNDBUF_BOOST_BYTES_RTT_LO, + SNDBUF_BOOST_BYTES_RTT_HI, + SNDBUF_BOOST_FACTOR); +} + +/** * tcp_update_seqack_wnd() - Update ACK sequence and window to guest/tap * @c: Execution context * @conn: Connection pointer @@ -1155,6 +1191,8 @@ int tcp_update_seqack_wnd(const struct ctx *c, struct tcp_tap_conn *conn, if ((int)sendq > SNDBUF_GET(conn)) /* Due to memory pressure? */ limit = 0; + else if ((int)tinfo->tcpi_snd_wnd > SNDBUF_GET(conn)) + limit = tcp_sndbuf_boost(conn, tinfo) - (int)sendq; else limit = SNDBUF_GET(conn) - (int)sendq; |