From gentoo kernel guide:
"The mm-sources are based on the development-sources and contain Andrew Morton's patch set. It assembles several other patches, like ext2/3 Extended Attributes and Access Control Lists, Page Table Sharing, the Orlov Allocator, non-linear mapping behaviour, etc into one patch set.
If you really want to live on the edge and you think development-sources are for wussies, then try out mm-sources."
So probably not good for a production server
Heres a link to an article on the patches: