> > I want to know if in the 2.4 kernel there is still 1GB of memory reserved for > > the kernel and 3GB for the user space, in a 4GB system, on x86 platform (AMD > > Athlon MP) ? > > Yes, unless you change the value of PAGE_OFFSET. Yes, there is a limit. I beg to differ from Joe. You cannot change this to get all 4G for the userspace process. This is another "32-bit virtualspace" issue. You cant get all your RAM from userspace because the virtualspace set aside for the kernel prevents you from using it to map physical memory. Look at /usr/src/linux/include/asm-i386/page.h Here is the a snippet from there. <<SNIP>> /* * This handles the memory map.. We could make this a config * option, but too many people screw it up, and too few need * it. * * 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 more physical memory than this then see the * CONFIG_HIGHMEM4G * and CONFIG_HIGHMEM64G options in the kernel configuration. */ <<END_OF_SNIP>> Setting this only means that the kernel can access all 4GB of memory. For memory above 950MB it can directly map, it needs to use dynamic mapping(kmap) The 3G limitation is imposed by the X-86 architecture. Maybe Rik Van Riel can elucidate further :) Regards. > > What is the maximum adressable memory for a user space process on the same > > system ? > > 3G, unless you change the value of PAGE_OFFSET. > > Cheers, > > -- Joe > -- > Kernelnewbies: Help each other learn about the Linux kernel. > Archive: http://mail.nl.linux.org/kernelnewbies/ > FAQ: http://kernelnewbies.org/faq/ > /dev/null devnull@adc.idt.com -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
