How to exclude an instance when dumping signals for Verdi?

[mochi]

I'm trying to find a way NOT to dump signals from selective module/instance.
I tried a few things so far, but it seems like all the signals are dumped and slows down the simulation significantly.
Does anybody know how to avoid dumping signals from a specific module?
BTW, I use irun (cadence) to simulate.

$fsdbDumpfile("dump.fsdb");
$fsdbDumpvars(0, top);
$fsdbDumpvars("+IO_Only", top.exclude_inst);

===

$fsdbDumpfile("dump.fsdb");
$fsdbDumpvars(0, top);
$fsdbDumpvars("+skip_cell_instance=0", top.exclude_inst);

Thanks!