Re: Hardware limits on numbers of threads?

[Ulrich Drepper <drepper@redhat.com>]

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Dan Kegel wrote:
> http://people.redhat.com/drepper/glibcthreads.html says:
> 
> 
>>Hardware restrictions put hard limits on the number of 
>>threads the kernel can support for each process. 
>>Specifically this applies to IA-32 (and AMD x86_64) where the thread
>>register is a segment register. The processor architecture 
>>puts an upper limit on the number of segment register values 
>>which can be used (8192 in this case).
> 
> 
> Is this true?  Where does the limit come from?

This was and is true with the kernel before 2.5.3<mumble> when Ingo 
introduced TLS support since the thread specific data had to be 
addressed via LDT entries and the LDT holds at most 8192 entries.  The 
GDT based solution now implemented in the kernel has no such limitation 
and the number of threads you can create with the new thread library is 
only limited by system resources.

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