sch_sfq: revert dont put new flow at the end of flows
authorEric Dumazet <eric.dumazet@gmail.com>
Tue, 13 Mar 2012 18:04:25 +0000 (18:04 +0000)
committerDavid S. Miller <davem@davemloft.net>
Fri, 16 Mar 2012 08:55:25 +0000 (01:55 -0700)
commitcc34eb672eedb5ff248ac3bf9971a76f141fd141
treec3bb99022ba73eb31440f5774e4c9e635be6721d
parent122bdf67f15a22bcabf6c2cab3a545d17ccf68dc
sch_sfq: revert dont put new flow at the end of flows

This reverts commit d47a0ac7b6 (sch_sfq: dont put new flow at the end of
flows)

As Jesper found out, patch sounded great but has bad side effects.

In stress situation, pushing new flows in front of the queue can prevent
old flows doing any progress. Packets can stay in SFQ queue for
unlimited amount of time.

It's possible to add heuristics to limit this problem, but this would
add complexity outside of SFQ scope.

A more sensible answer to Dave Taht concerns (who reported the issued I
tried to solve in original commit) is probably to use a qdisc hierarchy
so that high prio packets dont enter a potentially crowded SFQ qdisc.

Reported-by: Jesper Dangaard Brouer <jdb@comx.dk>
Cc: Dave Taht <dave.taht@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/sched/sch_sfq.c