How to interrupt Android boot sequence to force it boot to Linux kernel only I am trying to do some low level performance testing related to device processor cores through adb which I feel it is affected by Android background services and system stuff. 

As I know that the Android boot sequence stages are as follow:


Execute Boot ROM code. 
Execute the boot loader.
Load the Linux kernel.
Launch Zygote, which initializes the Dalvik VM.
System server which loads the Android system.


So my question is how can I interrupt this sequence to force it stop on stage 3 to load Linux kernel. This can help me implement my intermediary performance testings before loading again Android system.

Does Fastboot or Clockworkmod recovery can help here and load my device to a kind of Linux kernel?

Any hint will be appreciated.
Thanks.
No. Android's not like a desktop GNU/Linux distro, where you can press I to get an interactive boot, or skip X and just boot to a shell. The only way to achieve this would be to build your own custom ROM after editing the init scripts (which have much the same function as on a desktop GNU/Linux system) to tailor the boot process how you like.