On Mon, 20 Apr 2009 04:36:06 +0300 Izik Eidus <ieidus@xxxxxxxxxx> wrote: > Ksm is driver that allow merging identical pages between one or more > applications in way unvisible to the application that use it. > Pages that are merged are marked as readonly and are COWed when any > application try to change them. > > Ksm is used for cases where using fork() is not suitable, > one of this cases is where the pages of the application keep changing > dynamicly and the application cannot know in advance what pages are > going to be identical. > > Ksm works by walking over the memory pages of the applications it > scan in order to find identical pages. > It uses a two sorted data strctures called stable and unstable trees > to find in effective way the identical pages. > > When ksm finds two identical pages, it marks them as readonly and merges > them into single one page, > after the pages are marked as readonly and merged into one page, linux > will treat this pages as normal copy_on_write pages and will fork them > when write access will happen to them. > > Ksm scan just memory areas that were registred to be scanned by it. > > ... > + copy_user_highpage(kpage, page1, addr1, vma); > ... Breaks ppc64 allmodcofnig because that architecture doesn't export its copy_user_page() to modules. Architectures are inconsistent about this. x86 _does_ export it, because it bounces it to the exported copy_page(). So can I ask that you sit down and work out upon which architectures it really makes sense to offer KSM? Disallow the others in Kconfig and arrange for copy_user_highpage() to be available on the allowed architectures? Thanks. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
