[plt-scheme] Parallel execution

It's a quote from the lecture notes for an operating systems course: 
http://www.google.com.au/search?hs=Dfx&hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=%22Process+switch%3A+above+plus+MMU%2FTLB+state%22&btnG=Search&meta=

This is the most definate statement I could find regards threading in 
mzscheme: 
http://list.cs.brown.edu/pipermail/plt-scheme/2005-January/007640.html


Gregory Woodhouse wrote:

>
> On Jan 14, 2006, at 4:12 PM, Chongkai Zhu wrote:
>
>> PLT thread are user thread instead of kernal thread. Here is a  quoting:
>>
>> 1 Kernel threads:
>> – OS is aware of “thread” abstraction
>> – Each thread has separate OS state (ready, blocked,…)
>> – Kernel schedules threads rather than processes
>> – Kernel context switches between threads (and processes)
>>     = Thread switch: save/restore registers (inc. PC and SP)
>>     = Process switch: above plus MMU/TLB state
>>     = Thread switches cheaper than process (~10us vs ~30us)
>> 2 User threads:
>> – OS is unaware of “thread abstraction”
>> – User-level thread library implements abstraction
>> – Thread “context switch” performed entirely within user space
>> – Requires cooperation between threads to ensure fairness
>
>
> What are you quoting here?
>
> ===
> Gregory Woodhouse
> gregory.woodhouse at sbcglobal.net
>
> "A hero is no braver than an ordinary
> man, but he is brave five minutes longer."
> -- Ralph Waldo Emerson
>
>
>
> _________________________________________________
>  For list-related administrative tasks:
>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>