On Wed, 24 Aug 2005 21:36:51 -0000 (GMT) "christopher baus" <[EMAIL PROTECTED]> wrote:
> > The OS can address 2^32 or around 8gigs on 32 bit systems. Most OSes > limit the address space that can be used for applications. I believe it > is about 4 gigs on XP and 32bit Linux and 6gigs on Windows 2003 Server. > If you have more than 8gigs or memory you have to use overlays which is > PITA. I suspect that those that actually need that much address space > will use 64 bit processors. 2^32 is 4GiB ia32 architecture has a 32bit virtual address space modern ia32 chips support 36bit physical address space via Page Address Extension (PAE) Linux is typically split 3GiB UVA, 1Gib KVA You can compile linux to do a 4G KVA/4G UVA split (known as a 4gig/4gig kernel) Linux supports PAE, hence 64GiB of phys addr, though you'll run in lowmem exhaustion if you go much more than 8Gib unless you are using the 4gig/4gig kernel split. This is because linux maintains a memory map (struct page) of every page of memory on the system. This data structure lives in KVA. The more memory you have, the larger the mmap. WIth a 1G/3G split, you'll eat up too much of the 1G trying to map the physical memory If you move to 64bit processors, all of this uglieness goes away (i.e. Opteron/EM64T) - jim _______________________________________________ RLUG mailing list [email protected] http://lists.rlug.org/mailman/listinfo/rlug
