Re: Hardware limits on numbers of threads?

From: Ulrich Drepper (
Date: Wed Sep 18 2002 - 02:02:24 EST

Hash: SHA1

Dan Kegel wrote:
> 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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