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| author |   Neal Cardwell <ncardwell@google.com> | 2018-11-08 21:54:00 -0500 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2018-11-08 20:46:17 -0800 |
| commit | 1106a5ade15fa2effdbfb3b3a1ba560a536dbcfe (patch) | |
| tree | 03d0d2786c8901843b46448fe8270a29efdbb6b2 | |
| parent | Merge branch 'net-Use-__vlan_hwaccel_-helpers' (diff) | |
| download | linux-dev-1106a5ade15fa2effdbfb3b3a1ba560a536dbcfe.tar.xz linux-dev-1106a5ade15fa2effdbfb3b3a1ba560a536dbcfe.zip | |
tcp_bbr: update comments to reflect pacing_margin_percent
Recently, in commit ab408b6dc744 ("tcp: switch tcp and sch_fq to new
earliest departure time model"), the TCP BBR code switched to a new
approach of using an explicit bbr_pacing_margin_percent for shaving a
pacing rate "haircut", rather than the previous implict
approach. Update an old comment to reflect the new approach.
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/ipv4/tcp_bbr.c | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c index 9277abdd822a..0f497fc49c3f 100644 --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -128,7 +128,12 @@ static const u32 bbr_probe_rtt_mode_ms = 200; /* Skip TSO below the following bandwidth (bits/sec): */ static const int bbr_min_tso_rate = 1200000; -/* Pace at ~1% below estimated bw, on average, to reduce queue at bottleneck. */ +/* Pace at ~1% below estimated bw, on average, to reduce queue at bottleneck. + * In order to help drive the network toward lower queues and low latency while + * maintaining high utilization, the average pacing rate aims to be slightly + * lower than the estimated bandwidth. This is an important aspect of the + * design. + */ static const int bbr_pacing_margin_percent = 1; /* We use a high_gain value of 2/ln(2) because it's the smallest pacing gain @@ -247,13 +252,7 @@ static void bbr_init_pacing_rate_from_rtt(struct sock *sk) sk->sk_pacing_rate = bbr_bw_to_pacing_rate(sk, bw, bbr_high_gain); } -/* Pace using current bw estimate and a gain factor. In order to help drive the - * network toward lower queues while maintaining high utilization and low - * latency, the average pacing rate aims to be slightly (~1%) lower than the - * estimated bandwidth. This is an important aspect of the design. In this - * implementation this slightly lower pacing rate is achieved implicitly by not - * including link-layer headers in the packet size used for the pacing rate. - */ +/* Pace using current bw estimate and a gain factor. */ static void bbr_set_pacing_rate(struct sock *sk, u32 bw, int gain) { struct tcp_sock *tp = tcp_sk(sk); |