[PATCH] libcsupport: Have greedy allocations use consume extended memory

[Chris Johns]

On 9/2/21 12:37 am, Joel Sherrill wrote:
> On Mon, Feb 8, 2021 at 12:44 AM Chris Johns <chrisj at rtems.org
> <mailto:chrisj at rtems.org>> wrote:
> 
>     On 8/2/21 5:38 pm, Sebastian Huber wrote:
>     >
>     > On 08/02/2021 07:30, chrisj at rtems.org <mailto:chrisj at rtems.org> wrote:
>     >> diff --git a/cpukit/libcsupport/src/rtems_heap_greedy.c
>     >> b/cpukit/libcsupport/src/rtems_heap_greedy.c
>     >> index 4dda39873f..2361f17d2e 100644
>     >> --- a/cpukit/libcsupport/src/rtems_heap_greedy.c
>     >> +++ b/cpukit/libcsupport/src/rtems_heap_greedy.c
>     >> @@ -30,8 +30,20 @@ void *rtems_heap_greedy_allocate(
>     >>     size_t block_count
>     >>   )
>     >>   {
>     >> +  Heap_Control *heap = RTEMS_Malloc_Heap;
>     >> +  size_t size = 128 * 1024 * 1024;
>     >>     void *opaque;
>     >>   +  while (size > 0) {
>     >> +    opaque = (*rtems_malloc_extend_handler)( heap, size );
>     >> +    if (opaque == NULL) {
>     >> +      size >>= 1;
>     >> +    } else {
>     >> +      if ( rtems_malloc_dirty_helper != NULL )
>     >> +    (*rtems_malloc_dirty_helper)( opaque, size );
>     >> +    }
>     >> +  }
>     > You need a couple of more ' ' after and before the braces. Each if should
>     have a
>     > { }. Apart from the formatting it looks good.
> 
>     Thanks, I will fix the formatting and push.
> 
>     And there is no performance issue on hardware so that must be a psim thing.
> 
> 
> What performance issue do you think there could have been?

I do not know. I have never looked at how psim is implemented. I believe the
slow down inside the simulator.

> This must just be a side-effect of the PowerPC BSPs which have more than 32MB 
> RAM and want to support dynamically loading code. They must ensure that no
> branches or calls exceed 32MB from the current location. Thus it has to be loaded 
> early in program life before the heap is extended.

This is inside the simulator?

> Are there other supported architectures where code must fit into a subset of the
> address space where it could negatively impact dynamic loading?

ARM.

> How does the DL code deal with PPC code that is built without the -mlongcall 
> option?

libdl adds a trampoline ...

https://git.rtems.org/rtems/tree/cpukit/libdl/rtl-mdreloc-powerpc.c#n184

Chris

> EPICS discusses this here:
> 
> https://epics.anl.gov/base/ppc.php <https://epics.anl.gov/base/ppc.php>
> 
> --joel
> 
> 
>     Chris
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