if_bridge + polling get lower througphts

[Chih-Chang Hsieh]

We have a FreeBSD 6.1-PRELEASE box.

It runs with 2 em NICs and uses if_bridge + IPFW + ipfilter + pf.

This box usually gets a very high interrupt rate >90%.

By using netstat -I em0 1, we see:

input (em0) output
packets errs bytes packets errs bytes colls
15164 0 9549410 16842 0 12132262 0
15331 0 9220723 17466 0 12354486 0
16486 0 10089165 17926 0 13256014 0
14936 10 8363433 17090 0 13367271 0
14712 0 8449705 16701 0 13443079 0


When we enable the polling on em0 and em1 by ifconfig, netstat -I em0 shows:

input (em0) output
packets errs bytes packets errs bytes colls
10910 0 6629176 11467 0 7681346 0
10951 0 6916042 11397 0 7954205 0
11281 0 7437813 10804 0 7390386 0
10711 0 6308033 11605 0 8400405 0
10807 0 6270716 10973 0 7700748 0

the interrupt rate decreases (<30%) but we get lower throuphts.

The related sysctl MIBs are:

kern.polling.idlepoll_sleeping: 1
kern.polling.stalled: 0
kern.polling.suspect: 0
kern.polling.phase: 0
kern.polling.enable: 0
kern.polling.handlers: 0
kern.polling.residual_burst: 0
kern.polling.pending_polls: 0
kern.polling.lost_polls: 0
kern.polling.short_ticks: 0
kern.polling.reg_frac: 20
kern.polling.user_frac: 50
kern.polling.idle_poll: 1
kern.polling.each_burst: 5
kern.polling.burst_max: 1000
kern.polling.burst: 5

net.link.bridge.ipfw: 1
net.link.bridge.pfil_member: 1
net.link.bridge.pfil_bridge: 1
net.link.bridge.pfil_onlyip: 0

How could we tune the box to reach higher throughputs

as in non-polling mode?

Thanks in advance.