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I am newbie in windows driver development. I just want to know , a global variable in a driver will use paged pool memory or non paged pool memory ?
Thanks and Regards
Navaneeth
903
Non-paged memory pool is data in the computer's RAM used by the kernel and drivers of the operating system. The non-paged pool is never swapped to the disk (to the paging file), it is always stored only in the physical memory.
No - it's not necessarily true for either very old OR very new systems. A device with no swapping device ( e.g. very early PC's without hard drives ) would have zero paged memory.
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.
Paged pool is amount of kernel and device driver memory that CAN spill over from physical memory into the slow page file (source). Nonpaged pool is the amount of kernel and device driver memory that must stay in physical memory.
Depends. The Non paged pool should be reserved for memory that must stay in RAM so if you are doing something critical that would affected by a memory page from disk operation then use non paged.
See here for more info.
Looking at this (though it discusses c++ as opposed to C) it would seem that by default the globals can be located in either by #pragma. Also on p22 of this we see how to do this. Finally this discuss here we see that the data segment should be non pagagable by default.
192
Global variables in a kernel mode driver are allocated from NonPagedPool.
You can also use the device extension (when you call IoCreateDevice), it is always allocated from NonPaged memory.
I hope this helps, Martin
38
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