Friday, May 7, 2010

What are Pool Resources? -- Understanding Pool Resources

When a machine boots up, the Memory Manager creates two dynamically sized memory pools. These two pools are known as the Paged Pool and NonPaged Pool. Each of these pools start at an initial size that is based upon the amount of physical memory present in the system. Pool memory is a subset of available memory and is not necessarily contiguous. If necessary, these pools can grow up to a maximum size that is determined by the system at boot time.
what distinguishes Paged Pool and NonPaged Pool memory?
The first difference is that Paged Pool is exactly what its name implies - it can be paged out. The NonPaged Pool cannot be paged out. Drivers use the NonPaged Pool for many of their requirements because they can be accessed at any Interrupt Request Level (IRQL). The IRQL defines the hardware priority at which a processor operates at any given time.

Let's examine what type of items reside in each of these pools. Within the NonPaged pool, you would find handles that are used by applications in the user-mode space as well as Kernel-Mode drivers (typically ending in a .sys file extension). Examples of Paged Pool items are Token Objects, Kernel-Mode drivers and the Registry.

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