Polling or Interrupt based method

Question

When should one use polling method and when should one use interrupt based method ? Are there scenarios in which both can be used ?

Answer 1

It is much better to go with Interrupt based design compared to polling based because polling based is flawed in the sense that it expects the data to be returned on every poll. Now, you might say that I will get around this case where a single poll has returned me an error but why the heck waste all the CPU cycles polling for something when it could as well return an error ?? And to expect a poll might fail is practical product scenario.

Interrupt based designs make even more sense when there is a lot of layers of functions involved in a single poll. To me its a common practice: Would you keep asking (polling) your friend again & again everyday whether he has the information you need OR would you just tell him that interrupt me when you have the information I need. I think we do the right thing in day to day lives but fail to realize.

But interrupt based architectures when implemented require solid understanding of the publish-subscribe design principle. And, when done in app domains, they require the part of the code sending interrupts to be really well written. This good as it squeezes the complexity to one place as well.

Additional to above, following are the other advantages that polling based architecture provides you free of cost:

• Asynchrounous
• Fits well in case of infrequent events/updates
• Update only when there is data available scenarios
• Better error handling & management
• Better usage of CPU cycles
• Better battery life mgmt
• Keeps the listeners free from complexity underneath

Whenever you are designing sw & you have this choice, you should always choose an interrupt based design over polling based, because an interrupt based design can fill up for polling based situation using listeners but a polling based design can never fulfill the requirement needing interrupt based design.

Following is a brief comparison matrix:

                     -INTERRUPT-      -LOOP-
Speed                  fast            slow
Eficiency              good            poor
CPU waste              low             high
multitasking           yes             no
complexity             high            low
debugging              +/- easy        easy
critical in time       excellent       poor
code bloat             low impact      high impact