which says[emphasis mine]:

Unfortunately for kernel developers, allocating memory in the kernel
is not as simple as allocating memory in userspace. A number of
factors contribute to the complication, among them:
The kernel is limited to about 1GB of virtual and physical memory.
**The kernel's memory is not pageable.**

As per the documentation(https://www.oreilly.com

/library/view/linux-device-drivers/0596005903/ch08.html),

which says:

get_free_page and Friends

If a module needs to allocate big chunks of memory, it is usually 

better to use a page-oriented technique. 

I am confused after I have seen these two sayings.

I think they have the opposite meaning:

the former one clams that the kernel's memory is not pageable

whereas the latter one implicitly states there is a page-oriented 

technique  used by the kernel(i.e. function  get_free_page 

depends a page-oriented technique).

I have thought and thought about it for a long time, but I still don't

comprehend them.I would be grateful to have some help with this

question.

Thank you for your attention to this matter.