RE: What's the difference between Quantum and Timeslice ?

Thanks Raphael. 

I have got there differences now.

An addition question. In handle_timer_interrupt(schedule.cc), 
why useing  (get_prio_queue(current)->current_timeslice -= get_timer_tick_length()) <= 0 to determine 
whether end of a thread's timeslice?  
Why not just use "(tcb->current_timeslice -= get_timer_tick_length) <= 0". 

So as in end_of_timeslice():
tcb->current_timeslice = prio_queue->current_timeslice + tcb->timeslice_length;
prio_queue->current_timeslice = prio_queue->get(get_priority (tcb))->current_timeslice;

Why there must  a prio_queue->current_timeslice but not just use tcb->timeslice ?

Thank you for you time!

---
Best regards

Bo Liu



> Date: Thu, 18 Sep 2008 11:04:12 +0200
> From: [email protected]
> To: [email protected]; [email protected]
> Subject: Re: What's the difference between Quantum and Timeslice ?
>
> Hi Bob,
>
>> What's the difference between Quantum and Timeslice ?
>> Timeslice is used for thread scheduler. Then Quantum used for what ?
>
> A new timeslice is allocated every time a thread is scheduled and (only)
> serves to implement round-robin-scheduling: after at most "timeslice"
> time, the thread is preempted and another thread can be scheduled. The
> preempted thread may be scheduled again.
>
> The (total) quantum was intended to limit the total time the thread may
> spend executing on any CPU. It is decreased every time a timer interrupt
> occurs (just like timeslices are, see schedule.cc,
> handle_timer_interrupt()), but never reset automatically (only via a
> schedule syscall). Once a thread runs out of time (no quantum left), it
> will not be scheduled again (a preemption IPC should be sent to its
> scheduler, but that's disabled due to major problems, see scheduler.cc,
> total_quantum_expired()).
>
> In short, the timeslice determines for how long a thread can
> continuously occupy a CPU before being preempted, the quantum limits the
> total time the thread may spend on the CPUs accumulated over all
> occasions the thread was scheduled.
>
> Regards,
> Raphael

_________________________________________________________________
Discover the new Windows Vista
http://search.msn.com/results.aspx?q=windows+vista&mkt=en-US&form=QBRE