On Sunday 23 January 2005 08:11 pm, Jeff Dike wrote: > It'll allocate a temp file of the appropriate size. If it's larger than > what it can use for physical memory, the rest will be allocated as highmem. > If you leave 2-level pagetables on, then you're limited to 4G. If you turn > on 3-level pagetables, then you get up to 128G.
Interesting. I wonder how that works? (PAE on x86 only lets you have 64G.) > [EMAIL PROTECTED] said: > > Not unless it's unmapping and remapping multiple mmaps. > > It is. But an individual process running under UML can still only have 4 gigabytes. > > (There's > > large file support, but trying to mmap a 5 gig chunk out of a large > > file can't work: > > It does it a page at a time. > > > what would that mean? How could you generate an > > offset into the last meg? > > The LFS interfaces take 64-bit offsets. Yeah. (Ouch. But yeah, I can see that working...) > > What would the pointer _be_?) > > What pointer? The virtual or physical address used to access memory. (I'm guessing userspace programs running under UML are limited to 4 gigs, and UML is using page indexes and is thus limited to 4 billion pages, not 4 billion bytes.) > > The parent kernel's highmem support still doesn't provide more than 4 > > gigabytes per application, and the UML kernel is one application. > > The host kernel's highmem support is totally irrelevant. There doesn't > even need to be highmem support on the host. Just large file support, and the ability to mmap up to 4 gigs of memory at a time (with a starting offset potentially above 4 gigabytes), and unmap it and map a different 4 gigs when you switch to the next process... Makes my brain hurt just thinking about it, but that could be caffeine withdrawl... > Jeff Rob ------------------------------------------------------- This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting Tool for open source databases. Create drag-&-drop reports. Save time by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc. Download a FREE copy at http://www.intelliview.com/go/osdn_nl _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
