There's a CONFIG_HIGHMEM_4GB, which allows the *kernel* to see 4GB of physical addresses (without any highmem setting, the kernel can only see somewhat less than 1GB of physical RAM), but (AFAIK) does not change the user/kernel VM split. It might, but it does not have to. There's also CONFIG_HIGHMEM_64GB, which allows the kernel to see 64GB of physical RAM (assuming your motherboard manufacturer wasn't skimping on physical address lines -- many do exactly that), but again, there's no particular reason this should affect the VM split. Again, it might, but it does not have to.
Virtual address space has no bearing on the total amount of physical RAM your machine can use... if you need more VM for a process, split the single process into multiple processes. :-P
There's also "just move to 64-bit already!!", which is much easier in Linux than in Windows. As another bonus, in Linux, any still-32-bit user processes get 4GB of VM for free. And there's no pressure on the kernel that way, either, like there is if you change the kernel/user split. What a deal. ;-) |
