**diff options**

author | Eric Dumazet <edumazet@google.com> | 2012-07-29 20:52:21 +0000 |
---|---|---|

committer | David S. Miller <davem@davemloft.net> | 2012-08-10 16:52:54 -0700 |

commit | 2359a47671fc4fb0fe5e9945f76c2cb10792c0f8 (patch) | |

tree | 2ff0ca201a2797f26414dcfe5df90ededb94375b | |

parent | 55461ddbcb0b36d1575e01fb4f130c609ca1cfee (diff) | |

download | linux-2359a47671fc4fb0fe5e9945f76c2cb10792c0f8.tar.gz |

codel: refine one condition to avoid a nul rec_inv_sqrt

One condition before codel_Newton_step() was not good if
we never left the dropping state for a flow. As a result
rec_inv_sqrt was 0, instead of the ~0 initial value.
codel control law was then set to a very aggressive mode, dropping
many packets before reaching 'target' and recovering from this problem.
To keep codel_vars_init() as efficient as possible, refine
the condition to make sure rec_inv_sqrt initial value is correct
Many thanks to Anton Mich for discovering the issue and suggesting
a fix.
Reported-by: Anton Mich <lp2s1h@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

-rw-r--r-- | include/net/codel.h | 8 |

1 files changed, 6 insertions, 2 deletions

diff --git a/include/net/codel.h b/include/net/codel.h index 550debfc240..389cf621161 100644 --- a/include/net/codel.h +++ b/include/net/codel.h @@ -305,6 +305,8 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch, } } } else if (drop) { + u32 delta; + if (params->ecn && INET_ECN_set_ce(skb)) { stats->ecn_mark++; } else { @@ -320,9 +322,11 @@ static struct sk_buff *codel_dequeue(struct Qdisc *sch, * assume that the drop rate that controlled the queue on the * last cycle is a good starting point to control it now. */ - if (codel_time_before(now - vars->drop_next, + delta = vars->count - vars->lastcount; + if (delta > 1 && + codel_time_before(now - vars->drop_next, 16 * params->interval)) { - vars->count = (vars->count - vars->lastcount) | 1; + vars->count = delta; /* we dont care if rec_inv_sqrt approximation * is not very precise : * Next Newton steps will correct it quadratically. |