Using the kernel's powerful dynamic debug feature
The instrumentation approach to debugging – interspersing your kernel (and module) code with many printk is indeed a good technique. It helps you narrow things down and debug them! But as you've no doubt realized, there can be a (pretty high) cost to this:
- It eats into your disk (or flash) space as logs get filled in. This can be especially problematic on constrained embedded systems. Also, writing to disk is much slower than writing to RAM.
- It's fast in RAM, but the ring buffer is not that large and would thus quickly get overwhelmed; older prints will soon be lost.
- Even more important, on many production systems, a high volume of printks would have an adverse performance impact, creating bottlenecks and even possible livelocks! Rate limiting helps with this, to some extent...
A solution would be to use the pr_debug() and/or the dev_dbg() APIs! They're especially useful during development...
