Re: [dpdk-dev] [PATCH] eal:ppc: fix incorrect ifdef for ppc_64

[David Christensen <drc@linux.vnet.ibm.com>]

>> An ifdef present in eal_memory.c references "RTE_ARCH_PPC64" when
>> it should actually use "RTE_ARCH_PPC_64".  Simple testing revealed
>> that both the PPC_64 and non-PPC_64 versions of the code involved
>> work, but the PPC_64 version of the code is retained to be
>> consistent with other instances in the same file where mmapped
>> memory is accessed in reverse order on Power platforms.
> 
> The change itself is not that scary, but just reading this commitlog I
> fail to see the impact for an application.
> Can you share some light?
> 

As far as I can tell there is no impact on any applications.  The old 
code, which walked through the list in a forward direction, worked 
perfectly well with testpmd and DPDK pktgen applications on Power systems.

With the ifdef fixed, the core walks the list in the reverse direction 
as intended, the code still worked (i.e. no errors or problems were 
observed in the same test applications).

I'm not completely familiar with why memseg lists must be traversed in 
the reverse direction for Power systems.  It might be something specific 
to Power 8 systems which I'm not actually supporting on DPDK, only the 
Power 9 systems that I use for for development and testing.

Dave