Understanding Page Numbers In Pmap Output
The pmap command shows how a process uses virtual memory. Each row usually begins with a mapped address. That address points to the first byte of a memory region. A page number is found by dividing that address by the selected page size. Most Linux systems use 4096 byte pages, but huge pages and special kernels may use other values.
Why The Calculation Matters
Page numbers help analysts compare memory maps with kernel counters. They also help when reviewing dumps, page table notes, or allocator behavior. A raw hexadecimal address is useful, yet it can hide the real page boundary. Converting it makes the region easier to audit. You can see where a mapping starts, how many pages it spans, and where the last page ends.
How This Tool Reads Data
This calculator can read common pmap lines. It looks for a hexadecimal address followed by a size in K. It keeps the permission text and mapped file name when available. You may also enter one manual address. That is useful for isolated traces or short debugging notes. The page size can be changed before calculation.
Interpreting The Result
The start page is the zero based virtual page number. The offset shows how far the address sits inside its first page. When the offset is zero, the mapping starts on a clean boundary. Page count uses the mapping size and the starting offset. The end page shows the final page touched by the region. These numbers are estimates for analysis. They do not replace live kernel inspection.
Practical Review Tips
Use the same page size across related checks. Copy pmap output directly when possible. Remove unrelated log lines if the table looks noisy. Compare large mappings against resident and dirty memory columns separately. A large virtual span does not always mean heavy physical memory use. Shared libraries can also appear in many processes. Export the table when you need a repeatable record. Keep the source output beside the exported file for context.
For best accuracy, confirm the page size from system tools. Some workloads use transparent huge pages. Mixed page sizes need separate reviews, because one page size cannot describe every mapping correctly safely.