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1 | What: /sys/kernel/debug/kmemtrace/ | ||
2 | Date: July 2008 | ||
3 | Contact: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro> | ||
4 | Description: | ||
5 | |||
6 | In kmemtrace-enabled kernels, the following files are created: | ||
7 | |||
8 | /sys/kernel/debug/kmemtrace/ | ||
9 | cpu<n> (0400) Per-CPU tracing data, see below. (binary) | ||
10 | total_overruns (0400) Total number of bytes which were dropped from | ||
11 | cpu<n> files because of full buffer condition, | ||
12 | non-binary. (text) | ||
13 | abi_version (0400) Kernel's kmemtrace ABI version. (text) | ||
14 | |||
15 | Each per-CPU file should be read according to the relay interface. That is, | ||
16 | the reader should set affinity to that specific CPU and, as currently done by | ||
17 | the userspace application (though there are other methods), use poll() with | ||
18 | an infinite timeout before every read(). Otherwise, erroneous data may be | ||
19 | read. The binary data has the following _core_ format: | ||
20 | |||
21 | Event ID (1 byte) Unsigned integer, one of: | ||
22 | 0 - represents an allocation (KMEMTRACE_EVENT_ALLOC) | ||
23 | 1 - represents a freeing of previously allocated memory | ||
24 | (KMEMTRACE_EVENT_FREE) | ||
25 | Type ID (1 byte) Unsigned integer, one of: | ||
26 | 0 - this is a kmalloc() / kfree() | ||
27 | 1 - this is a kmem_cache_alloc() / kmem_cache_free() | ||
28 | 2 - this is a __get_free_pages() et al. | ||
29 | Event size (2 bytes) Unsigned integer representing the | ||
30 | size of this event. Used to extend | ||
31 | kmemtrace. Discard the bytes you | ||
32 | don't know about. | ||
33 | Sequence number (4 bytes) Signed integer used to reorder data | ||
34 | logged on SMP machines. Wraparound | ||
35 | must be taken into account, although | ||
36 | it is unlikely. | ||
37 | Caller address (8 bytes) Return address to the caller. | ||
38 | Pointer to mem (8 bytes) Pointer to target memory area. Can be | ||
39 | NULL, but not all such calls might be | ||
40 | recorded. | ||
41 | |||
42 | In case of KMEMTRACE_EVENT_ALLOC events, the next fields follow: | ||
43 | |||
44 | Requested bytes (8 bytes) Total number of requested bytes, | ||
45 | unsigned, must not be zero. | ||
46 | Allocated bytes (8 bytes) Total number of actually allocated | ||
47 | bytes, unsigned, must not be lower | ||
48 | than requested bytes. | ||
49 | Requested flags (4 bytes) GFP flags supplied by the caller. | ||
50 | Target CPU (4 bytes) Signed integer, valid for event id 1. | ||
51 | If equal to -1, target CPU is the same | ||
52 | as origin CPU, but the reverse might | ||
53 | not be true. | ||
54 | |||
55 | The data is made available in the same endianness the machine has. | ||
56 | |||
57 | Other event ids and type ids may be defined and added. Other fields may be | ||
58 | added by increasing event size, but see below for details. | ||
59 | Every modification to the ABI, including new id definitions, are followed | ||
60 | by bumping the ABI version by one. | ||
61 | |||
62 | Adding new data to the packet (features) is done at the end of the mandatory | ||
63 | data: | ||
64 | Feature size (2 byte) | ||
65 | Feature ID (1 byte) | ||
66 | Feature data (Feature size - 4 bytes) | ||
67 | |||
68 | |||
69 | Users: | ||
70 | kmemtrace-user - git://repo.or.cz/kmemtrace-user.git | ||
71 | |||