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>"This simplifies some things since you can allocate and access any physical page without creating new mapping." I am curious what types of things does this si
by bogomipz 9y ago
>"This simplifies some things since you can allocate and access any physical page without creating new mapping."
I am curious what types of things does this simply for the kernel? When is a physical page allocation ever done that doesn't need to be entered in into a page table entry?
- tedunangst 9y agoptrace of another process, for instance.
- bogomipz 9y agoCan you elaborate? If I strace a process which makes a ptrace system call that is just another userland process and my userland process has a page table entry just like any other userland process.
- tedunangst 9y agoYou call ptrace and ask to read another process's memory. The kernel has to turn the requested VA in that address space into a physical page (walking those page tables, not yours) then copy the memory (from some VA in kernel space). This is quicker if you can turn a PA into a VA by simply adding an offset.
- bogomipz 9y agoI see. I misinterpreted your previous comment. Cheers.