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Rev 2927 | Rev 4691 | ||
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1 | Memory management |
1 | Memory management |
2 | ================= |
2 | ================= |
3 | 3 | ||
4 | 1. Virtual Address Translation |
4 | 1. Virtual Address Translation |
5 | 5 | ||
6 | 1.1 Hierarchical 4-level per address space page tables |
6 | 1.1 Hierarchical 4-level per address space page tables |
7 | 7 | ||
8 | SPARTAN kernel deploys generic interface for 4-level page tables |
8 | SPARTAN kernel deploys generic interface for 4-level page tables for these |
9 | for these architectures: amd64, ia32, mips32 and ppc32. In this |
9 | architectures: amd64, arm32, ia32, mips32 and ppc32. In this setting, page |
10 | setting, page tables are hierarchical and are not shared by |
10 | tables are hierarchical and are not shared by address spaces (i.e. one set of |
11 | address spaces (i.e. one set of page tables per address space). |
11 | page tables per address space). |
12 | 12 | ||
13 | 13 | ||
14 | VADDR |
14 | VADDR |
15 | +-----------------------------------------------------------------------------+ |
15 | +-----------------------------------------------------------------------------+ |
16 | | PTL0_INDEX | PTL1_INDEX | PTL2_INDEX | PTL3_INDEX | OFFSET | |
16 | | PTL0_INDEX | PTL1_INDEX | PTL2_INDEX | PTL3_INDEX | OFFSET | |
17 | +-----------------------------------------------------------------------------+ |
17 | +-----------------------------------------------------------------------------+ |
18 | 18 | ||
19 | 19 | ||
20 | PTL0 PTL1 PTL2 PTL3 |
20 | PTL0 PTL1 PTL2 PTL3 |
21 | +--------+ +--------+ +--------+ +--------+ |
21 | +--------+ +--------+ +--------+ +--------+ |
22 | | | | | | PTL3 | -----\ | | |
22 | | | | | | PTL3 | -----\ | | |
23 | | | | | +--------+ | | | |
23 | | | | | +--------+ | | | |
24 | | | +--------+ | | | | | |
24 | | | +--------+ | | | | | |
25 | | | | PTL2 | -----\ | | | | | |
25 | | | | PTL2 | -----\ | | | | | |
26 | | | +--------+ | | | | | | |
26 | | | +--------+ | | | | | | |
27 | | | | | | | | | +--------+ |
27 | | | | | | | | | +--------+ |
28 | +--------+ | | | | | | | FRAME | |
28 | +--------+ | | | | | | | FRAME | |
29 | | PTL1 | -----\ | | | | | | +--------+ |
29 | | PTL1 | -----\ | | | | | | +--------+ |
30 | +--------+ | | | | | | | | | |
30 | +--------+ | | | | | | | | | |
31 | | | | | | | | | | | | |
31 | | | | | | | | | | | | |
32 | | | | | | | | | | | | |
32 | | | | | | | | | | | | |
33 | +--------+ \----> +--------+ \----> +--------+ \----> +--------+ |
33 | +--------+ \----> +--------+ \----> +--------+ \----> +--------+ |
34 | ^ |
34 | ^ |
35 | | |
35 | | |
36 | | |
36 | | |
37 | +--------+ |
37 | +--------+ |
38 | | PTL0 | |
38 | | PTL0 | |
39 | +--------+ |
39 | +--------+ |
40 | 40 | ||
41 | 41 | ||
42 | PTL0 Page Table Level 0 (Page Directory) |
42 | PTL0 Page Table Level 0 (Page Directory) |
43 | PTL1 Page Table Level 1 |
43 | PTL1 Page Table Level 1 |
44 | PTL2 Page Table Level 2 |
44 | PTL2 Page Table Level 2 |
45 | PTL3 Page Table Level 3 |
45 | PTL3 Page Table Level 3 |
46 | 46 | ||
47 | PTL0_INDEX Index into PTL0 |
47 | PTL0_INDEX Index into PTL0 |
48 | PTL1_INDEX Index into PTL1 |
48 | PTL1_INDEX Index into PTL1 |
49 | PTL2_INDEX Index into PTL2 |
49 | PTL2_INDEX Index into PTL2 |
50 | PTL3_INDEX Index into PTL3 |
50 | PTL3_INDEX Index into PTL3 |
51 | 51 | ||
52 | VADDR Virtual address for which mapping is looked up |
52 | VADDR Virtual address for which mapping is looked up |
53 | FRAME Physical address of memory frame to which VADDR is mapped |
53 | FRAME Physical address of memory frame to which VADDR is mapped |
54 | 54 | ||
55 | 55 | ||
56 | On architectures whose hardware has fewer levels, PTL2 and, if need be, PTL1 are |
56 | On architectures whose hardware has fewer levels, PTL2 and, if need be, PTL1 are |
57 | left out. TLB-only architectures are to define custom format for software page |
57 | left out. TLB-only architectures are to define custom format for software page |
58 | tables. |
58 | tables. |
59 | 59 | ||
60 | 1.2 Single global page hash table |
60 | 1.2 Single global page hash table |
61 | 61 | ||
62 | Generic page hash table interface is deployed on 64-bit architectures without |
62 | Generic page hash table interface is deployed on 64-bit architectures without |
63 | implied hardware support for hierarchical page tables, i.e. ia64 and sparc64. |
63 | implied hardware support for hierarchical page tables, i.e. ia64 and sparc64. |
64 | There is only one global page hash table in the system shared by all address |
64 | There is only one global page hash table in the system shared by all address |
65 | spaces. |
65 | spaces. |
66 | 66 | ||
67 | 67 | ||
68 | 2. Memory allocators |
68 | 2. Memory allocators |
69 | 69 | ||
70 | 2.1 General allocator |
70 | 2.1 General allocator |
71 | 71 | ||
72 | 'malloc' function accepts flags as a second argument. The flags are directly |
72 | 'malloc' function accepts flags as a second argument. The flags are directly |
73 | passed to the underlying frame_alloc function. |
73 | passed to the underlying frame_alloc function. |
74 | 74 | ||
75 | 1) If the flags parameter contains FRAME_ATOMIC, the allocator will not sleep. |
75 | 1) If the flags parameter contains FRAME_ATOMIC, the allocator will not sleep. |
76 | The allocator CAN return NULL, when memory is not directly available. |
76 | The allocator CAN return NULL, when memory is not directly available. |
77 | The caller MUST check if NULL was not returned |
77 | The caller MUST check if NULL was not returned |
78 | 78 | ||
79 | 2) If the flags parameter does not contain FRAME_ATOMIC, the allocator |
79 | 2) If the flags parameter does not contain FRAME_ATOMIC, the allocator |
80 | will never return NULL, but it CAN sleep indefinitely. The caller |
80 | will never return NULL, but it CAN sleep indefinitely. The caller |
81 | does not have to check the return value. |
81 | does not have to check the return value. |
82 | 82 | ||
83 | 3) The maximum size that can be allocated using malloc is 256K |
83 | 3) The maximum size that can be allocated using malloc is 256K |
84 | 84 | ||
85 | Rules 1) and 2) apply to slab_alloc as well. Using SLAB allocator |
85 | Rules 1) and 2) apply to slab_alloc as well. Using SLAB allocator |
86 | to allocate too large values is not recommended. |
86 | to allocate too large values is not recommended. |
87 | 87 | ||
88 | 88 |