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Core Development Tools/Discussion/General/shm_ctl() fails with SHMCTL_PHYS|SHMCTL_GLOBAL on ARM target/List of Posts
Forum Topic - shm_ctl() fails with SHMCTL_PHYS|SHMCTL_GLOBAL on ARM target: (5 Items)
   
Update
Ken Schumm
09/22/2008 2:47 PM
post13783
shm_ctl() fails with SHMCTL_PHYS|SHMCTL_GLOBAL on ARM target   
We're trying to optimize performance of our pxa270 product.

Towards that end we want to map in a region of the processors internal on-chip SRAM as shared memory.

When using SHMCTL_PHYS|SHMCTL_GLOBAL flags, shm_ctl() returns errno 89 (Function not implemented).

If we leave off the SHMCTL_GLOBAL then the code works but we need to map it GLOBAL to prevent the cache flush on context
 switch slowdown that occurs with this cache design.

The docs indicate this should be possible.

Anyone know anything about this?
Aleksandar Ristovski(deleted)
09/22/2008 2:55 PM
post13786
Re: shm_ctl() fails with SHMCTL_PHYS|SHMCTL_GLOBAL on ARM target   
Ken Schumm wrote:
> We're trying to optimize performance of our pxa270 product.
> 
> Towards that end we want to map in a region of the processors internal on-chip SRAM as shared memory.
> 
> When using SHMCTL_PHYS|SHMCTL_GLOBAL flags, shm_ctl() returns errno 89 (Function not implemented).
> 
> If we leave off the SHMCTL_GLOBAL then the code works but we need to map it GLOBAL to prevent the cache flush on 
context switch slowdown that occurs with this cache design.
> 
> The docs indicate this should be possible.
> 
> Anyone know anything about this?


I think you will get a better/faster response to your question if you post it to OSTech forum.
Ken Schumm
09/22/2008 3:31 PM
post13791
Re: shm_ctl() fails with SHMCTL_PHYS|SHMCTL_GLOBAL on ARM target   
[...]

> > Anyone know anything about this?
> 
> 
> I think you will get a better/faster response to your question if you post it 
> to OSTech forum. 

You're probably right, thanks, I posted the question over there.
Andy Gryc(deleted)
09/22/2008 2:57 PM
post13787
Re: shm_ctl() fails with SHMCTL_PHYS|SHMCTL_GLOBAL on ARM target   
If you're just trying to access physical memory, how about trying mmap instead?
Ken Schumm
09/22/2008 3:26 PM
post13789
Re: shm_ctl() fails with SHMCTL_PHYS|SHMCTL_GLOBAL on ARM target   
> If you're just trying to access physical memory, how about trying mmap instead
> ?


Accessing the memory isn't a problem, accessing it efficiently is. Without the SHMCTL_GLOBAL flag the cache flushes on 
every context switch.

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