When the terms "user space" and "kernel space" are used, do they refer to
the physical memory of the machine (RAM, actually present) or to the virtual
memory (4 GB on 32-bit machines, just virtual) ?
the physical memory of the machine (RAM, actually present) or to the virtual
memory (4 GB on 32-bit machines, just virtual) ?
The term kernel spacerefer to set of addresses that contain's kernel code+kernel related structures. In most OS such as linux,the kernel space can't be swapped or paged out.
The user space refers to an area of the memory used by user mode applications. Depending on
context , this space of addresses could either mean physical or virtual.
I have read somewhere, that kernel threads always have "mm" member of
their task_struct pointing to "NULL" (task.mm->NULL). Is that correct?
their task_struct pointing to "NULL" (task.mm->NULL). Is that correct?
The task.mm is NULL because a kernel thread never accesses the user space portion.
On 9/1/05, Paul Duplys <kernel_newbie@xxxxxx> wrote:
Hi all,
I have 2 generall questions to the address spaces in kernel:
1) When the terms "user space" and "kernel space" are used, do they refer to
the physical memory of the machine (RAM, actually present) or to the virtual
memory (4 GB on 32-bit machines, just virtual) ?
2) IWhen the terms "user space" and "kernel space" are used, do they refer to
the physical memory of the machine (RAM, actually present) or to the virtual
memory (4 GB on 32-bit machines, just virtual) ?
Regards,
Paul
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