I Googled a lot about L4 microkernel and found that very less resources are there on L4.
What are some good links I can refer ?
Is there any application of L4 (i.e. where it is used) ?
L4 supposedly passed one billion installs a year ago, so, the short answer is yes. According to my reading, Linux running on top of L4 is factors faster than running alone, making for a Linux L4, and Android has been ported to L4 on top of linux. My view, is if so many installs are running, why can't we have L4 available to us through a shell, such ksh or bash? The short answer is drivers; it was chosen for us by the L4 gods that L4 should be Linux to support drivers, even though Linux is short on drivers. There is a little about it here on this community wiki: http://alopex.li/wiki/L4FiascoTutorial
And the rationale for L4/Linux here: http://www.slideshare.net/sartakov/03-advanced-components
If drivers are so problematic, such that free software prevents commercial vendors from writing them, then why not create a "qt" version for driver writers, that is to say a public domain kit that unifies computer functionality to define drivers. Then OS writers would create the backend for their OS such that the vendor only has to do the work once.
The other useful topic is the idea of a VM over L4, using Perl Parrot VM (PVM) as a hypothetical example; if L4 could be modified to run strictly in registers.... imagine the performance
L4 is a family of microkernels sharing a more or less common API and some base ideas/concepts.
Typical applications are hard-realtime/high availability scenarios as well as a
usage as hypervisor hosting more traditional operating systems.
There is an L4 kernel from ok-labs.com which was for example used in the Motorola Evoke
to run the application stack side by side with the baseband stack on the same processor.
A kernel from ok-labs is also used to host the baseband-stack of the iPad2.
sysgo.com has a kernel called PikeOS which they use for aerospace/defense applications.
According to Andrew Tanenbaum L4 is used in cell phones (fifth from last answer, or you can do a text search for "L4"). Unfortunately, I haven't managed to find much other than the L4 website, and FIASCO.