[Kernel] SMP and IRQ – case (2011-Sep)

In SMP system, to save power, not all cpus are active if system is not heavy loaded.
But let’s image this case.
System is not heavy loaded – only cpu0 is active, but at some moment IRQ is issued very often in short time.
In this case, some of issued IRQs may be abandoned.

Let’s assume a IC does abnormal operation if issued interrupt is not handled by MPU and system status is like above.
Then, system works abnormally when it is not loaded, but system works well when it is loaded.
(This is opposite of usual case. Most case, system may do abnormal operation when it is loaded.)
default IRQ affinity is usually, masked for all cores – IRQ can be handled by any cpu.
And, more than one cpus are active when system is loaded. So, there is less chance for IRQ to be abandoned – these are several cpus to handle!

This case shows very interesting issues at system!


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s