[LAU] LADSPA processing time for audio zeroes

When a LADSPA plugin is being sent zeroes-- i.e. when the volume of the input data is down to nothing-- is it still sucking up CPU cycles? I understand from the JACK API that anytime a client gets a callback with data, it has to drop down and deal with the data and then return, even if the data is zero. But that could be lightweight, if the data are zero, or is that very compute-intensive for the plugin? I'm trying to build an outboard effects chain in various LADSPA hosts (JACK Rack, ecasound, AMS, others... haven't settled on one yet), and when I've got that plugin's volume MIDI'ed down to zero, I'd like it to not be dominating CPU cycles at that time. -ken