Get Memory Mapping Parameters

Why Memory Map Information Is Required

• Memory mapping parameters can be obtained from the Linux^® memory management subsystem
• A Linux memory mapping descriptor serves as a master dictionary for an entire address space, tracking everything from a process's virtual memory areas to its active page tables and memory usage. The information tracked includes:
  • Linux kernel memory map page size: default is 4 KB
  • The start physical address of kernel page structures
  • The maximum number of mapped pages
  • The size of the page structure
  • The offset of  page_type in the page structure
  • The offset of private in the page structure
• Memory map information tells at91bootstrap or the PC memmap tool which DRAM pages are valid and should be included in the snapshot

How to Obtain Memory Mapping Information

• Memmap Linux Module
  • Once your Linux system is up and running, you can then load the memmap module, which will output the memory mapping parameters to the console
    • For Manually Save and Load SnapshotImage mode only
• Get Memory Mapping Parameters in Auto mode
  • Once your Linux system enters Suspend mode, the Ultra-Fast Boot patch enables the power manager routine to save all memory mapping parameters to secure RAM
  • The at91bootstrap reads these parameters from secure RAM to analyze the memory mapping
    • For Automatically Save and Load Snapshot Image mode only
• Linux Ultra-Fast Boot patch (see the "Apply Kernel Patch to Support Ultra-Fast Boot" page)
  • During the Linux kernel boot, these memory mapping parameters are printed to the console.
    • For Load Pre-Saved Snapshot Image mode only