Monday, March 14, 2011

Page Table Entry (PTE) Flags

In a 32-bit Windows Operating System, Bits 0 to 11 in a PTE stands for different memory management flags associated with the Page table referred to by that PTE. Following are small description for some of the important ones:

 - Accessed: Page has been read.
 - Copy-On-Write: Usually for shared memory. When are process Write on these pages, a copy is made and the copy is made private to that process.
 - Dirty: Page has been written to.
 - Global: Translation applies to all the process. Translation Buffer (TLB) flush does not affect this PTE.
 - Prototype: Sw Flag used as a construct for sharing the memory.
 - Valid: Translate to Valid Physical Memory.
 - Write: Indicate whether the page is writable.

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