Re: linux-2.6.1 x86_64 : STACK_TOP and text/data

[dada1]

Andi Kleen wrote:

> You're right. Thanks for reporting this. This seems to be a 2.6 
> specific bug, it didn't happen in 2.4.
>
> I will fix it. It should definitely use PAGE_OFFSET for 64bit 
> processes and 4GB for !3GB 32bit processes.
>
> -Andi
>
>
>  
Another thing I noticed in last glibc CVS (nptl)

Thread stacks are also allocated in the 1GB quadrant :

nptl/sysdeps/x86_64/pthreaddef.h
/* We prefer to have the stack allocated in the low 4GB since this
  allows faster context switches.  */      
#define ARCH_MAP_FLAGS MAP_32BIT 

Is this really true ?
Is memory allocated in the low 4GB is faster on x86_64  (64bit kernel, 
64 bit user prog ?)

Thank you

Eric Dumazet


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