[Click] why do we add idle->Todevice with each PollDevice ?

[ahmed A.]

hello,

Please could any one explain to me why do we add Idle-> ToDevice (eth0) to
a configuration file, when we have PollDevice(eth0) running on the same
interface ?
I got warning messages saying without the Idle-> ToDevice (eth0), I will
get Bad performance , why is that? I would expect adding a ToDevice will
consume some
CPU cycles and degrade the performance rather than improving it ....


I would appreciate any help or tips.

Thanks,
Ahmed