PMEM 2M aligned issue

[tanghaodong25]

If the pmem is mounted as 2M aligned, the pmem obj address can't be registered as rdma buffer. We need to mount pmem as 4K aligned, but the pmem write performance is worse than it with 2M aligned.

2M aligned (default)
ndctl create-namespace -r region0 -f -e namespace0.0 -m devdax
4K aligned
ndctl create-namespace -r region0 -f -e namespace0.0 -m devdax -a 4k

[zhouyuan]

we could set the alignment at pool level:
https://github.com/pbalcer/nvml/blob/6f2136f379c9a44ad73315ab2075fe665e02bcf7/src/test/obj_ctl_alignment/obj_ctl_alignment.c