1 ================== 1 ==================
2 Memblock simulator 2 Memblock simulator
3 ================== 3 ==================
4 4
5 Introduction 5 Introduction
6 ============ 6 ============
7 7
8 Memblock is a boot time memory allocator[1] th 8 Memblock is a boot time memory allocator[1] that manages memory regions before
9 the actual memory management is initialized. I 9 the actual memory management is initialized. Its APIs allow to register physical
10 memory regions, mark them as available or rese 10 memory regions, mark them as available or reserved, allocate a block of memory
11 within the requested range and/or in specific 11 within the requested range and/or in specific NUMA node, and many more.
12 12
13 Because it is used so early in the booting pro 13 Because it is used so early in the booting process, testing and debugging it is
14 difficult. This test suite, usually referred a 14 difficult. This test suite, usually referred as memblock simulator, is
15 an attempt at testing the memblock mechanism. 15 an attempt at testing the memblock mechanism. It runs one monolithic test that
16 consist of a series of checks that exercise bo 16 consist of a series of checks that exercise both the basic operations and
17 allocation functionalities of memblock. The ma 17 allocation functionalities of memblock. The main data structure of the boot time
18 memory allocator is initialized at the build t 18 memory allocator is initialized at the build time, so the checks here reuse its
19 instance throughout the duration of the test. 19 instance throughout the duration of the test. To ensure that tests don't affect
20 each other, region arrays are reset in between 20 each other, region arrays are reset in between.
21 21
22 As this project uses the actual memblock code 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 23 some of the kernel definitions were stubbed by the initial commit that
24 introduced memblock simulator (commit 16802e55 24 introduced memblock simulator (commit 16802e55dea9 ("memblock tests: Add
25 skeleton of the memblock simulator")) and a fe 25 skeleton of the memblock simulator")) and a few preparation commits just
26 before it. Most of them don't match the kernel 26 before it. Most of them don't match the kernel implementation, so one should
27 consult them first before making any significa 27 consult them first before making any significant changes to the project.
28 28
29 Usage 29 Usage
30 ===== 30 =====
31 31
32 To run the tests, build the main target and ru 32 To run the tests, build the main target and run it:
33 33
34 $ make && ./main 34 $ make && ./main
35 35
36 A successful run produces no output. It is pos !! 36 A successful run produces no output. It is also possible to override different
37 by passing options from command line. For exam !! 37 configuration parameters. For example, to simulate enabled NUMA, use:
38 append the `-v` options when you run the tests <<
39 <<
40 $ ./main -v <<
41 <<
42 This will print information about which functi <<
43 number of test cases that passed. <<
44 <<
45 For the full list of options from command line <<
46 <<
47 It is also possible to override different conf <<
48 the test functions. For example, to simulate e <<
49 38
50 $ make NUMA=1 39 $ make NUMA=1
51 40
52 For the full list of build options, see `make !! 41 For the full list of options, see `make help`.
53 42
54 Project structure 43 Project structure
55 ================= 44 =================
56 45
57 The project has one target, main, which calls 46 The project has one target, main, which calls a group of checks for basic and
58 allocation functions. Tests for each group are 47 allocation functions. Tests for each group are defined in dedicated files, as it
59 can be seen here: 48 can be seen here:
60 49
61 memblock 50 memblock
62 |-- asm ------------------, 51 |-- asm ------------------,
63 |-- lib |-- implement 52 |-- lib |-- implement function and struct stubs
64 |-- linux ------------------' 53 |-- linux ------------------'
65 |-- scripts 54 |-- scripts
66 | |-- Makefile.include -- handles `m 55 | |-- Makefile.include -- handles `make` parameters
67 |-- tests 56 |-- tests
68 | |-- alloc_api.(c|h) -- memblock_a 57 | |-- alloc_api.(c|h) -- memblock_alloc tests
69 | |-- alloc_helpers_api.(c|h) -- memblock_a 58 | |-- alloc_helpers_api.(c|h) -- memblock_alloc_from tests
70 | |-- alloc_nid_api.(c|h) -- memblock_a 59 | |-- alloc_nid_api.(c|h) -- memblock_alloc_try_nid tests
71 | |-- basic_api.(c|h) -- memblock_a 60 | |-- basic_api.(c|h) -- memblock_add/memblock_reserve/... tests
72 | |-- common.(c|h) -- helper fun 61 | |-- common.(c|h) -- helper functions for resetting memblock;
73 |-- main.c --------------. dummy phys 62 |-- main.c --------------. dummy physical memory definition
74 |-- Makefile `- test runne 63 |-- Makefile `- test runner
75 |-- README 64 |-- README
76 |-- TODO 65 |-- TODO
77 |-- .gitignore 66 |-- .gitignore
78 67
79 Simulating physical memory 68 Simulating physical memory
80 ========================== 69 ==========================
81 70
82 Some allocation functions clear the memory in 71 Some allocation functions clear the memory in the process, so it is required for
83 memblock to track valid memory ranges. To achi 72 memblock to track valid memory ranges. To achieve this, the test suite registers
84 with memblock memory stored by test_memory str 73 with memblock memory stored by test_memory struct. It is a small wrapper that
85 points to a block of memory allocated via mall 74 points to a block of memory allocated via malloc. For each group of allocation
86 tests, dummy physical memory is allocated, add 75 tests, dummy physical memory is allocated, added to memblock, and then released
87 at the end of the test run. The structure of a 76 at the end of the test run. The structure of a test runner checking allocation
88 functions is as follows: 77 functions is as follows:
89 78
90 int memblock_alloc_foo_checks(void) 79 int memblock_alloc_foo_checks(void)
91 { 80 {
92 reset_memblock_attributes(); /* da 81 reset_memblock_attributes(); /* data structure reset */
93 dummy_physical_memory_init(); /* al 82 dummy_physical_memory_init(); /* allocate and register memory */
94 83
95 (...allocation checks...) 84 (...allocation checks...)
96 85
97 dummy_physical_memory_cleanup(); /* fr 86 dummy_physical_memory_cleanup(); /* free the memory */
98 } 87 }
99 88
100 There's no need to explicitly free the dummy m 89 There's no need to explicitly free the dummy memory from memblock via
101 memblock_free() call. The entry will be erased 90 memblock_free() call. The entry will be erased by reset_memblock_regions(),
102 called at the beginning of each test. 91 called at the beginning of each test.
103 92
104 Known issues 93 Known issues
105 ============ 94 ============
106 95
107 1. Requesting a specific NUMA node via membloc 96 1. Requesting a specific NUMA node via memblock_alloc_node() does not work as
108 intended. Once the fix is in place, tests f 97 intended. Once the fix is in place, tests for this function can be added.
109 98
110 2. Tests for memblock_alloc_low() can't be eas 99 2. Tests for memblock_alloc_low() can't be easily implemented. The function uses
111 ARCH_LOW_ADDRESS_LIMIT marco, which can't b 100 ARCH_LOW_ADDRESS_LIMIT marco, which can't be changed to point at the low
112 memory of the memory_block. 101 memory of the memory_block.
113 102
114 References 103 References
115 ========== 104 ==========
116 105
117 1. Boot time memory management documentation p 106 1. Boot time memory management documentation page:
118 https://www.kernel.org/doc/html/latest/core 107 https://www.kernel.org/doc/html/latest/core-api/boot-time-mm.html
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