RFC eliminating zeroing of heap/workspace

[norume at aps.anl.gov (Eric Norum)]

Nothing in the C standard nor in the RTEMS documentation promises  
anything about the contents of dynamically allocated memory (other  
than calloc, and that routine clears the memory itself before handing  
back the pointer).  I'd say don't bother with the clearing.  A 30x  
speedup sounds worthwhile to me.


On Apr 5, 2007, at 3:58 PM, Joel Sherrill wrote:

> Hi,
>
> I have done some investigation on a simulator
> and determined that much of the time required
> to bring the minimum test from reset to the
> first task is consumed by zero'ing the
> C Program Heap and RTEMS Workspace.
>
> My testing is on a simulated system which
> has 4MB of RAM and zeroes all but maybe
> 64K of it since that is the code and data.
> It takes 97% of the boot time to clear this
> much RAM.
>
> What's the general sentiment about clearing:
>
> + the C program heap
> + the RTEMS workspace
>
> Just wanting opinions and thoughts.
>
> --joel
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-- 
Eric Norum <norume at aps.anl.gov>
Advanced Photon Source
Argonne National Laboratory
(630) 252-4793