Re: Large SGA in Linux?

Gene wrote:
>
> Anyone running Oracle 8.0.5.X on a Red Hat 6.0 box with a
> large SGA?
>
> I have a Dell server with 2gigs of RAM. If I modify the
> /usr/src/linux/include/asm/shmparam.h to set SHMMAX to
> 1gig and rebuild the kernel, changing nothing else, I can
> get a 500-600meg SGA (which is what I want). However, linux
> by default only recognizes upto 1gig of physical RAM. Therefore,
> I have changed the PAGE_OFFSET value in
> /usr/src/linux/include/asm/page.h (and the other file noted in the
> text of page.h) to 0X80000000 (the hex value of 2 gigs) to use my extra
> memory. Now, however, when I rebuilt the kernel I get all of my memory,
> but I can only allocate a shared memory segment of around 180megs.
> Anything larger than that fails.
>
> I cannot for the life of me figure out what is going wrong here.
>
> Any ideas?
>
> Thanks,
> Gene...

Did you change /usr/src/linux/arch/i386/vmlinux.lds as well? Here is the excerpt from page.h (I upgraded my kernel to 2.2.11 and I don't have any problems. My advice to you is to do the same.)

• A __PAGE_OFFSET of 0xC0000000 means that the kernel has
• a virtual address space of one gigabyte, which limits the
• amount of physical memory you can use to about 950MB. If
• you want to use more physical memory, change this define. *
• For example, if you have 2GB worth of physical memory, you
• could change this define to 0x80000000, which gives the
• kernel 2GB of virtual memory (enough to most of your physical memory
• as the kernel needs a bit extra for various io-memory mappings) *
• IF YOU CHANGE THIS, PLEASE ALSO CHANGE *
• arch/i386/vmlinux.lds *
• which has the same constant encoded..

--
Mladen Gogala Received on Fri Aug 27 1999 - 23:04:54 CDT