Re: KSE, libpthread & libthr: almost newbie question

Scott Long wrote:
> Robert Watson wrote:
>>
>> On Sat, 28 Oct 2006, Julian Elischer wrote:
>>
>>> Robert Watson wrote:
>>>>
>>>> On Fri, 27 Oct 2006, Julian Elischer wrote:
>>>>
>>>>> there is class of problems (e.g. some java programs) that have 
>>>>> THOUSANDS of threads, each representing an active aspect of some 
>>>>> object. How do you put an rlimit on that without either 1/ stopping 
>>>>> the program from working or 2/ allowing thousands of threads to 
>>>>> exist but not screwing other users.
>>>>
>>>> Does the JVM actually expose thousands of threads to the OS, or does 
>>>> it actually do its own M:N threading internally based on its 
>>>> execution model? My impression is the latter, exposing threads to 
>>>> the OS only when it needs them to consume kernel or CPU resources.
>>>
>>> I don't know the answer to that question, only that there is a class 
>>> of program style that uses this model.
>>
>> FYI, last night following comments about the change away "green 
>> threads", I ran some simple tests with the 1.4.2 JVM.  It appears 
>> that, at least in my simple test cases, all threads created in the JVM 
>> are exposed to the OS. Typically this appears to be about n+8 to n+9 
>> threads, where n is the number of threads created by the application 
>> itself, and 8/9 is the number created by the JVM.  I assume the 
>> variance of one is likely the garbage collector kicking in every now 
>> and then (or something along those lines).
>>
> 
> This is correct.  The JVM maps all threads directly into the native 
> threading mechanism provided by the OS.  'Green threads' have been 
> defunct since Java 1.3, and no other magic happens behind the scenes.
> 

so, why does it use 1:1 threads?
who knows what the thinking here was?

> Scott
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