What are the knobs to try and get OpenSolaris as low latency as possible.

In particular I'm trying to do this with the "igb" driver on OS 2009.06 and TCP.

I have set these so far for TCP:

# increase max tcp window
# Rule-of-thumb: max_buf = 2 x cwnd_max (congestion window)
ndd -set /dev/tcp tcp_max_buf 4194304
ndd -set /dev/tcp tcp_cwnd_max 2097152

# increase DEFAULT tcp window size
ndd -set /dev/tcp tcp_xmit_hiwat 1048576
ndd -set /dev/tcp tcp_recv_hiwat 1048576

# Disable Nagle
ndd -set /dev/tcp tcp_naglim_def 1

# if we aren't routing disable ip forwarding
ndd -set /dev/ip ip_forwarding 0

But they seem to concentrate more on being able to handle throughput
then latency.

I tried setting:

set dld:dld_opt = 2

in /etc/systerm to disable network stack automatic interrupt
adjustment, but that caused the igb driver to panic.

Is there anything anybody else has done to lower latency even if it's
at the cost of increased cpu?

-Ross
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