Linux內存管理之活動內存區

Linux內存活動區域其實就是全局變量e820中的內存塊做了相關的檢查和對其處理後的區域。在管理區初始化等地方有用到。

數據結構

1. struct node_active_region {
2. unsigned long start_pfn;
3. unsigned long end_pfn;
4. int nid;
5. };

初始化

活動內存的初始化工作在setup_arch()->initmem_init()->e820_register_active_regions()中

1. /* Walk the e820 map and register active regions within a node */
2. void __init e820_register_active_regions(int nid, unsigned long start_pfn,
3. unsigned long last_pfn)
4. {
5. unsigned long ei_startpfn;
6. unsigned long ei_endpfn;
7. int i;
9. for (i = 0; i < e820.nr_map; i++)
10. if (e820_find_active_region(&e820.map[i],/*從全局變量e820中查找活動區*/
11. start_pfn, last_pfn,
12. &ei_startpfn, &ei_endpfn))
13. add_active_range(nid, ei_startpfn, ei_endpfn);/*加入活動區*/
14. }

1. /*
2. * Finds an active region in the address range from start_pfn to last_pfn and
3. * returns its range in ei_startpfn and ei_endpfn for the e820 entry.
4. */
5. int __init e820_find_active_region(const struct e820entry *ei,
6. unsigned long start_pfn,
7. unsigned long last_pfn,
8. unsigned long *ei_startpfn,
9. unsigned long *ei_endpfn)
10. {
11. u64 align = PAGE_SIZE;
13. *ei_startpfn = round_up(ei->addr, align) >> PAGE_SHIFT;
14. *ei_endpfn = round_down(ei->addr + ei->size, align) >> PAGE_SHIFT;
16. /* Skip map entries smaller than a page */
17. if (*ei_startpfn >= *ei_endpfn)
18. return 0;
20. /* Skip if map is outside the node */
21. if (ei->type != E820_RAM || *ei_endpfn <= start_pfn ||
22. *ei_startpfn >= last_pfn)
23. return 0;
25. /* Check for overlaps */
26. if (*ei_startpfn < start_pfn)
27. *ei_startpfn = start_pfn;
28. if (*ei_endpfn > last_pfn)
29. *ei_endpfn = last_pfn;
31. return 1;
32. }

1. /*添加活動區域，需要對原有的進行檢查*/
2. void __init add_active_range(unsigned int nid, unsigned long start_pfn,
3. unsigned long end_pfn)
4. {
5. int i;
7. mminit_dprintk(MMINIT_TRACE, "memory_register",
8. "Entering add_active_range(%d, %#lx, %#lx) "
9. "%d entries of %d used\n",
10. nid, start_pfn, end_pfn,
11. nr_nodemap_entries, MAX_ACTIVE_REGIONS);
12. //not set macro
13. mminit_validate_memmodel_limits(&start_pfn, &end_pfn);
15. /* Merge with existing active regions if possible */
16. for (i = 0; i < nr_nodemap_entries; i++) {
17. if (early_node_map[i].nid != nid)
18. continue;
20. /* Skip if an existing region covers this new one */
21. if (start_pfn >= early_node_map[i].start_pfn &&
22. end_pfn <= early_node_map[i].end_pfn)
23. return;
25. /* Merge forward if suitable */
26. if (start_pfn <= early_node_map[i].end_pfn &&
27. end_pfn > early_node_map[i].end_pfn) {
28. early_node_map[i].end_pfn = end_pfn;
29. return;
30. }
32. /* Merge backward if suitable */
33. if (start_pfn < early_node_map[i].end_pfn &&
34. end_pfn >= early_node_map[i].start_pfn) {
35. early_node_map[i].start_pfn = start_pfn;
36. return;
37. }
38. }
40. /* Check that early_node_map is large enough */
41. if (i >= MAX_ACTIVE_REGIONS) {
42. printk(KERN_CRIT "More than %d memory regions, truncating\n",
43. MAX_ACTIVE_REGIONS);
44. return;
45. }
47. early_node_map[i].nid = nid;
48. early_node_map[i].start_pfn = start_pfn;
49. early_node_map[i].end_pfn = end_pfn;
50. nr_nodemap_entries = i + 1;
51. }