| Name | Size | Last modified (GMT) | Description | |
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| Parent directory | 2024-10-29 14:06:28 | ||
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| asm/ | 2024-10-29 14:06:27 | ||
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| lib/ | 2024-10-29 14:06:27 | ||
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| linux/ | 2024-10-29 14:06:27 | ||
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| scripts/ | 2024-10-29 14:06:27 | ||
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| tests/ | 2024-10-29 14:06:27 | ||
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| Makefile | 1767 bytes | 2024-10-29 14:06:27 | |
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| README | 4579 bytes | 2024-10-29 14:06:27 | |
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| TODO | 114 bytes | 2024-10-29 14:06:27 | |
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| internal.h | 491 bytes | 2024-10-29 14:06:27 | |
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| main.c | 464 bytes | 2024-10-29 14:06:27 | |
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| mmzone.c | 349 bytes | 2024-10-29 14:06:27 |
1 ==================
2 Memblock simulator
3 ==================
4
5 Introduction
6 ============
7
8 Memblock is a boot time memory allocator[1] that manages memory regions before
9 the actual memory management is initialized. Its APIs allow to register physical
10 memory regions, mark them as available or reserved, allocate a block of memory
11 within the requested range and/or in specific NUMA node, and many more.
12
13 Because it is used so early in the booting process, testing and debugging it is
14 difficult. This test suite, usually referred as memblock simulator, is
15 an attempt at testing the memblock mechanism. It runs one monolithic test that
16 consist of a series of checks that exercise both the basic operations and
17 allocation functionalities of memblock. The main data structure of the boot time
18 memory allocator is initialized at the build time, so the checks here reuse its
19 instance throughout the duration of the test. To ensure that tests don't affect
20 each other, region arrays are reset in between.
21
22 As this project uses the actual memblock code and has to run in user space,
23 some of the kernel definitions were stubbed by the initial commit that
24 introduced memblock simulator (commit 16802e55dea9 ("memblock tests: Add
25 skeleton of the memblock simulator")) and a few preparation commits just
26 before it. Most of them don't match the kernel implementation, so one should
27 consult them first before making any significant changes to the project.
28
29 Usage
30 =====
31
32 To run the tests, build the main target and run it:
33
34 $ make && ./main
35
36 A successful run produces no output. It is possible to control the behavior
37 by passing options from command line. For example, to include verbose output,
38 append the `-v` options when you run the tests:
39
40 $ ./main -v
41
42 This will print information about which functions are being tested and the
43 number of test cases that passed.
44
45 For the full list of options from command line, see `./main --help`.
46
47 It is also possible to override different configuration parameters to change
48 the test functions. For example, to simulate enabled NUMA, use:
49
50 $ make NUMA=1
51
52 For the full list of build options, see `make help`.
53
54 Project structure
55 =================
56
57 The project has one target, main, which calls a group of checks for basic and
58 allocation functions. Tests for each group are defined in dedicated files, as it
59 can be seen here:
60
61 memblock
62 |-- asm ------------------,
63 |-- lib |-- implement function and struct stubs
64 |-- linux ------------------'
65 |-- scripts
66 | |-- Makefile.include -- handles `make` parameters
67 |-- tests
68 | |-- alloc_api.(c|h) -- memblock_alloc tests
69 | |-- alloc_helpers_api.(c|h) -- memblock_alloc_from tests
70 | |-- alloc_nid_api.(c|h) -- memblock_alloc_try_nid tests
71 | |-- basic_api.(c|h) -- memblock_add/memblock_reserve/... tests
72 | |-- common.(c|h) -- helper functions for resetting memblock;
73 |-- main.c --------------. dummy physical memory definition
74 |-- Makefile `- test runner
75 |-- README
76 |-- TODO
77 |-- .gitignore
78
79 Simulating physical memory
80 ==========================
81
82 Some allocation functions clear the memory in the process, so it is required for
83 memblock to track valid memory ranges. To achieve this, the test suite registers
84 with memblock memory stored by test_memory struct. It is a small wrapper that
85 points to a block of memory allocated via malloc. For each group of allocation
86 tests, dummy physical memory is allocated, added to memblock, and then released
87 at the end of the test run. The structure of a test runner checking allocation
88 functions is as follows:
89
90 int memblock_alloc_foo_checks(void)
91 {
92 reset_memblock_attributes(); /* data structure reset */
93 dummy_physical_memory_init(); /* allocate and register memory */
94
95 (...allocation checks...)
96
97 dummy_physical_memory_cleanup(); /* free the memory */
98 }
99
100 There's no need to explicitly free the dummy memory from memblock via
101 memblock_free() call. The entry will be erased by reset_memblock_regions(),
102 called at the beginning of each test.
103
104 Known issues
105 ============
106
107 1. Requesting a specific NUMA node via memblock_alloc_node() does not work as
108 intended. Once the fix is in place, tests for this function can be added.
109
110 2. Tests for memblock_alloc_low() can't be easily implemented. The function uses
111 ARCH_LOW_ADDRESS_LIMIT marco, which can't be changed to point at the low
112 memory of the memory_block.
113
114 References
115 ==========
116
117 1. Boot time memory management documentation page:
118 https://www.kernel.org/doc/html/latest/core-api/boot-time-mm.html
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