Linux Kernel Architecture

Chapter3:MemoryManagement

be constructed from this information. Recall that architectures are required to established the following

information during boot:

❑ The page frame boundaries of the various zones in the system as stored in themax_zone_pfn

array.

❑ The distribution of page frames across nodes as stored in the global variableearly_node_map.

ManagingData Structure Creation

Starting with kernel 2.6.10, a generic framework was provided to transfer this information into the node

and zone data structures expected by the buddy system; before this, each architecture had to set up the

structures on its own. Today, it suffices to set up the aforementioned simple structures and leave the hard

work tofree_area_init_nodes. Figure 3-27 shows an overview of the process, and Figure 3-28 shows

the code flow diagram forfree_area_init_nodes.

free_area_init_nodes

Fill in pg_data_t

early_node_map

Architecture-Specific Setup

initialization

Set max page

frame numbers

for zones

(max_zone_pfns)

pg_data_t

Generic representation

of nodes and zones

Figure 3-27: Overview of the interplaybetween architecture-specific and

generic kernel code for setting up node and zone data memory management

data structures.

Determine zone

boundaries

Iterate over all nodes

free_area_init_nodes

free_area_init_node

calculate_node_totalpages

alloc_node_mem_map

free_area_init_core

check_for_regular_memory

Figure 3-28: Code flow diagram for

free_area_init_nodes.