On Tue, Feb 24, 2015 at 02:36:25PM -0800, D. Cooper Stevenson wrote: > Hello All, > > I read the Linus's release for RC1. One of his favorite features in the > release are, "actually some vm cleanups, where this release is getting rid > of the largely unused non-linear remapping code (replaced with just > emulating it with lots of smaller mappings) and unifies the NUMA and > PROTNONE handling for page tables." > > I understand that non-linear page remapping is unused (and, presumably, > reduces the code base size) but according to the remap_file_pages man page > (http://man7.org/linux/man-pages/man2/remap_file_pages.2.html) non-linear > system will be, "eventually be replaced by a slower in-kernel emulation." > > Was this a change of necessity? What gives?
As with all cleanups it's not necessary, but it makes life easier. It removed >1.5k lines of non-trivial code from critical path of the kernel. It's rarely used and tend to be error-prone. And developers need to be aware about exists of non-linear mapping while implementing new features. For instance, faultaround feature I've implemented was broken for non-linear mapping for some time and it took time to track it down. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
