From b8fc328668a74e1314a19266755a54abd875e5a6 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 29 Jul 2012 20:52:21 +0000 Subject: [PATCH] codel: refine one condition to avoid a nul rec_inv_sqrt commit 2359a47671fc4fb0fe5e9945f76c2cb10792c0f8 upstream. 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 Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/codel.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/include/net/codel.h +++ b/include/net/codel.h @@ -305,6 +305,8 @@ static struct sk_buff *codel_dequeue(str } } } 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(str * 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.