sched_4BSD

[Julian Elischer]

Sarath Kamisetty wrote:

>Hi,
>
>How does Linux handle this ? Any idea ?
>  
>

If you make 1000 threads, you get 1000 slots on the scheduler. (last 
time I looked..
Let me know if I'm wrong).

The guy next to you with 'vi' gets 1 slot..
who gets more cpu?



>Thanks,
>Sarat
>
>On Mon, 28 Feb 2005 00:26:10 -0800, Julian Elischer <julian at elischer.org> wrote:
>  
>
>>Ashwin Chandra wrote:
>>    
>>
>>>I wanted to get some clarification about the 4BSD scheduler. I am sort of
>>>confused why there are two forms of scheduling, one done between processes and
>>>another done between threads in a process. The priority calculations seem to be
>>>done only with processes and I assume that the global run queue holds processes,
>>>not threads. Also why is there only 1 run queue for 1 CPU. What happens to
>>>blocked processes and ready to be runned processes?
>>>      
>>>
>>Part of the challenge of adding threads to a system is to make it hard for a
>>threaded process to "flood" the system run queues so that other processes
>>get no cpu time.
>>
>>The scheme in the current freeBSD schedulers is a "crude" method, by which
>>only a limitted number of threads per process are allowed to be added to
>>the system run queue. RUnnable hreads fo r aprocess are kept on a run queue for
>>the process and only the highest N prioriy  hreads are actually put on the
>>system run queue.
>>
>>This is by no means the best way, but rather the
>>easiest way. I am hoping that some PhD candidate somewhere will decide
>>that thread scheduling is his topic and will figure out a better way
>>of doing this.
>>
>>both run queues hold threads. This is still a place wjere a lot
>>of work can be done.
>>
>>:-)
>>
>>
>>    
>>
>>>Ash
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>>>      
>>>
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>>
>>    
>>