Re: [PATCH] netem: fix rate extension and drop accounting

On Tue, 2012-07-03 at 11:25 +0200, Eric Dumazet wrote:

From: Eric Dumazet <edumazet@google.com>

commit 7bc0f28c7a0c (netem: rate extension) did wrong maths when packet
is enqueued while queue is not empty.

Result is unexpected cumulative delays

# tc qd add dev eth0 root est 1sec 4sec netem delay 200ms rate 100kbit
# ping -i 0.1 172.30.42.18
PING 172.30.42.18 (172.30.42.18) 56(84) bytes of data.
64 bytes from 172.30.42.18: icmp_req=1 ttl=64 time=208 ms
64 bytes from 172.30.42.18: icmp_req=2 ttl=64 time=424 ms
64 bytes from 172.30.42.18: icmp_req=3 ttl=64 time=838 ms
64 bytes from 172.30.42.18: icmp_req=4 ttl=64 time=1142 ms
64 bytes from 172.30.42.18: icmp_req=5 ttl=64 time=1335 ms
64 bytes from 172.30.42.18: icmp_req=6 ttl=64 time=1949 ms
64 bytes from 172.30.42.18: icmp_req=7 ttl=64 time=2450 ms
64 bytes from 172.30.42.18: icmp_req=8 ttl=64 time=2840 ms
64 bytes from 172.30.42.18: icmp_req=9 ttl=64 time=3121 ms
64 bytes from 172.30.42.18: icmp_req=10 ttl=64 time=3291 ms
64 bytes from 172.30.42.18: icmp_req=11 ttl=64 time=3784 ms

This patch also fixes a double drop accounting in case packet is dropped
in tfifo_enqueue()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <redacted>
Cc: Andreas Terzis <redacted>
Cc: Mark Gordon <redacted>
Cc: Hagen Paul Pfeifer <redacted>
---

Hmm, I'll send a v2