secondary process fails to initialize memory

spp_vf and spp_mirror sometime fail with the following log message at initialization.

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Jan 07 15:25:09 spp-s5 spp_vf[31829]: EAL: Cannot get a virtual area at requested address: 0x7ffbefe00000 (got 0x7ffbe8000000)
Jan 07 15:25:09 spp-s5 spp_vf[31829]: EAL: Could not mmap 17179869184 bytes at [0x7ffbefe00000] - please use '--base-virtaddr' option
Jan 07 15:25:09 spp-s5 spp_vf[31829]: EAL: Cannot preallocate VA space for hugepage memory
Jan 07 15:25:09 spp-s5 spp_vf[31829]: EAL: FATAL: Cannot init memory
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As a result of the investigation, it turned out that the problem arises for the following reasons.
The primary process(without --base-virtaddr) mmaps the memory segments to the address left to the system.
A secondary process tries to mmap the memory segments to the same address as primary.
At this time, a thread already operating in the secondary process may have already mmaped the same address.

One workaround is to specify an address that the system does not select for the --base-virtaddr option when starting the primary process.

Note that this problem occurs in DPDK v18.08 or earlier.
In v18.11, the mmap address of the memory segments starts from 0x100000000 without specifying the --base-virtaddr option. (Equivalent to specifying 0x100000000 for --base-virtaddr)