What is *Paged* Kernel Memory?

Question

What is paged kernel memory, as reported in the Windows Task Manager? Is it related to the page file?

I assumed that it was the part of kernel memory stored on disk in a page file, but I tested disabling my page file and (after restarting) still found paged kernel memory to be non-zero!

Solution

Excerpts from this:

Paged and nonpaged pools serve as the memory resources that the operating system and device drivers use to store their data structures.

The kernel and device drivers use nonpaged pool to store data that might be accessed when the system can’t handle page faults.

Kernel memory is memory allocated/used by the operating system itself, this includes the kernel and any drivers.

Paged kernel memory can be written to a page file, if one exists.

Nonpaged kernel memory will not ever be written to a page file. A "nonpaged memory pool" is needed to provide memory in situations where Windows cannot use page faults, such as while it is processing interrupts or deferred procedure calls (which is related to interrupts).

Comments

[Jamie Hanrahan]

This (the task manager display, not @LawrenceC's answer) is yet another example of poorly chosen wording in Windows' performance-related displays. "Pageable kernel pool" would be better. "Pageable" meaning it can be paged out, not necessarily that it has been. Some fraction of the pageable pool will be in RAM on any system; if you have no pagefile that fraction will be 1.0. But even without a pagefile the pageable pool is allocated and used separately from the nonpageable pool. And I would use the word "pool" instead of "memory" because there's a lot of kernel memory other than the pools.

[Jamie Hanrahan]

^ Furthermore, pieces of the paged pool can be "paged out" even with no pagefile. It would still be in RAM but would be on the modified page list or standby list, from where it can be brought back in with a "soft page fault".