On Wed, 06 Feb 2013 23:19:26 +0530, jeshkumar555@gmail.com said:
Can anyone suggest a good tutorial to create our own scheduler ?
Doing an I/O scheduler is pretty trivial, and there's a number of examples in-tree already to look at. If you mean a CPU scheduler, the major reason why there's no tutorial is because writing a non-toy scheduler is *hard*, and by and large anybody who's a good enough kernel hacker to write a working scheduler doesn't need a tutorial. Why is it hard? Lots of reasons. Even on a single-core, single-thread CPU, it's hard to go a good job of picking the next task to run, mostly because tasks are so damned good at changing behavior. You decide that it would be good to run an I/O bound task, so you pick a task that went into an I/O wait its last 12 times on the CPU - at which point the task turns around and goes CPU bound crunching all the data it read in the last 12 times. :) You also have interactions with thermal issues and frequency governors (usually, cranking to highest frequency and doing race-to-idle and then dropping to lowest freq results in the lowest total energy use, but especially for high-density applications, there may be a upper limit on watts per second that you can cool, resulting in trade-offs being needed). Then there's cache affinity issues, balancing load across cores on multi-socket systems, etc etc etc...