Re: Max number of threads with NPTL

Nathan Bryant wrote:
> Daniel Malmkvist wrote:
> 
>> To my supprise i could not have more then ~3500 threads at the same time.
>> I got a OutOfMemoryException, but there was plenty of system memory left
>> (the JVM only ha about 10% of system physical memory).
>>  
>>
> Address space might be a limiting factor in a 32-bit machine. Assuming a 
> 3gig/1gig VM split, you have less than a megabyte per thread stack at 
> 3500 threads, even assuming there is no other memory overhead, and there 
> is a lot of other overhead... Did you try using the Thread constructor 
> that specifies a stack size? Try specifying a single page - 4K.
> 
> You might also need to increase the maximum size of the Java heap. (Or 
> decrease it to make room for more stack?) I have found that it can't 
> grow beyond 1.5gig on x86.
> 
> If you are allocating the default stack size which is probably fairly 
> large, 

Default stack size is 512k. You need 3500 * 512k = 1750M address space
for 3500 threads. Try -Xss96k. Also check your limit on max #processes
(ulimit -u), you can't create more threads than that limit either.

regards,
-hui

          the system won't appear to be using the memory because the stack
> pages won't have corresponding physical pages allocated by the VM until 
> they are used - the stacks grow down. But they are still allocated 
> virtual address space within the process.
> 
> 
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