So, irqbalance has made a huge difference: now with heavy torrenting, the ping latency is ~20ms (vs 11ms ideal) at 45/9 (the link is 50/10). Setting SQM speed to 47.5/9.5 makes the latency go to 50..100ms and higher.
@moeller0, now that I am no longer CPU bound, how can I further improve SQM on my router? DO I still need to disable gro/lro/gso/tso ? My current SQM settings are below.
config queue 'wan'
option interface 'pppoe-wan'
option debug_logging '0'
option verbosity '5'
option linklayer 'ethernet'
option qdisc_advanced '1'
option qdisc_really_really_advanced '1'
option iqdisc_opts 'nat dual-dsthost'
option eqdisc_opts 'nat dual-srchost'
option squash_dscp '1'
option squash_ingress '1'
option ingress_ecn 'ECN'
option egress_ecn 'NOECN'
option overhead '34'
option enabled '1'
option qdisc 'cake'
option script 'piece_of_cake.qos'
option download '45000'
option upload '9000'