On Thu, 2008-08-28 at 12:29 +0530, Sukanto Ghosh wrote:
> Hi,
> 
> What was the reason for changing the CFS mechanism from
> fair_clock/wait_runtime to vruntime?

Numerical integrety mostly.

> What were the kind of workloads where the fairclock approach faired badly ?

They are analytically identical - its the discrete version of the
fair_clock code that led to unfixable numerical pain.

> Also, when adding a blocked task to the runqueue (rbtree), why is it's
> vruntime set to less than min_vruntime ?
> This means it would preempt the currently running process.
> If we have some processes which run for some (very less) time and get
> blocked repeatedly, won't the processes at the end of runqueue starve
> ....  because some or the other blocked process gets unblocked and gets
> the cpu (as vruntime is lesser than min_vruntime).

It never gets puts left of its previous value, so starvation cannot
happen.


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