On Mon, 2006-06-12 at 09:20 -0400, Jerry Feldman wrote:
This is not entirely true. An application not only has its own memory component, it also has shared libraries and a bunch of other things. If the kernel is PAE aware, the application can also avail itself of these features. I was reading a Sybase paper on the Adaptive Server Enterprise which does this. But, even if a 32-bit application itself is not PAE aware, it can utilize then extended memory indirectly.
Any PAE kernel can map any process beyond 4GiB or whatever is physically paged into user-space memory (which is 3GiB or lower). It's when the application is using more than those user-space limits, let alone the _hard_ 32-bit/4GiB limit, that you've at least have to modify how it is built, if not select interaction in the code itself (such as between major modules). An application may still load if not. And an application will very much croak if it attempts to allocate and work on more memory than the base memory model limits at any one time. You can have up to 64GiB of physical RAM in PAE, but you can't have anything address more than 4GiB at any time -- before we even look at user-space/memory model constraints.
From a server I/O standpoint, depends on your kernel model, more and more kernel-space memory becomes a _major_ issue when using the 3G/1G model. Especially if it's tapping in from PAE 36-bit areas, that eats up reserved kernel memory -- taking away from memory mapped I/O.
Again, more than 1-2GiB on a server -- and I don't care what OS -- you should be on AMD64, *PERIOD*. I hate to seemingly "flaunt my resume," but I tell you this from experience integrating Opteron all over the financial industry the last 2 years. User-space is the least concern -- especially when user-space takes away from kernel space that is very much needed from memory mapped I/O and other reservations. -- Bryan J. Smith Professional, technical annoyance mailto:b.j.smith@ieee.org http://thebs413.blogspot.com ------------------------------------------------------- Illegal Immigration = "Representation Without Taxation" -- Check the headers for your unsubscription address For additional commands send e-mail to suse-linux-e-help@suse.com Also check the archives at http://lists.suse.com Please read the FAQs: suse-linux-e-faq@suse.com