[GSoC] Bdbuf Improvements

[Xiang Cui]

Hi

The Bdbuf is the block device buffer management in RTEMS. It
implements a cache between the disk devices and file systems.

In general, the ultimate goal of the project is to make the Bdbuf and
related API more flexible as well as high performance by taking some
kind of refactoring.

It will take me some time to fully understand the Bdbuf and related
api. It scared me when I saw machine diagram at first glance  [1] ;-)

What I want to do now is to add some codes to gather statistics from
Bdbuf. The hit rate or miss rate should be given to evaluate cache
algorithms. I think it could be better if the statistics can give us
some hints to tune the Bdbuf configure. So I need some suggestions
about what statistics we need to gather. There is a command
"bdbuf_show", would these statistics be printed in similar way?

I just start to play with Bdbuf. If I made mistakes, please point them
out.  Any discuss or suggestions are welcomed.

Have a nice day.

Best regards,
Xiang

[1] http://www.rtems.org/onlinedocs/doxygen/cpukit/html/group__rtems__bdbuf.html#details