4a80b24bb2
Corrected the ABI description and the kmemtrace usage guide. Thanks to Randy Dunlap for noticing these errors. Signed-off-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro> Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
71 lines
2.7 KiB
Text
71 lines
2.7 KiB
Text
What: /sys/kernel/debug/kmemtrace/
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Date: July 2008
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Contact: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
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Description:
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In kmemtrace-enabled kernels, the following files are created:
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/sys/kernel/debug/kmemtrace/
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cpu<n> (0400) Per-CPU tracing data, see below. (binary)
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total_overruns (0400) Total number of bytes which were dropped from
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cpu<n> files because of full buffer condition,
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non-binary. (text)
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abi_version (0400) Kernel's kmemtrace ABI version. (text)
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Each per-CPU file should be read according to the relay interface. That is,
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the reader should set affinity to that specific CPU and, as currently done by
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the userspace application (though there are other methods), use poll() with
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an infinite timeout before every read(). Otherwise, erroneous data may be
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read. The binary data has the following _core_ format:
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Event ID (1 byte) Unsigned integer, one of:
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0 - represents an allocation (KMEMTRACE_EVENT_ALLOC)
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1 - represents a freeing of previously allocated memory
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(KMEMTRACE_EVENT_FREE)
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Type ID (1 byte) Unsigned integer, one of:
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0 - this is a kmalloc() / kfree()
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1 - this is a kmem_cache_alloc() / kmem_cache_free()
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2 - this is a __get_free_pages() et al.
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Event size (2 bytes) Unsigned integer representing the
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size of this event. Used to extend
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kmemtrace. Discard the bytes you
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don't know about.
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Sequence number (4 bytes) Signed integer used to reorder data
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logged on SMP machines. Wraparound
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must be taken into account, although
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it is unlikely.
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Caller address (8 bytes) Return address to the caller.
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Pointer to mem (8 bytes) Pointer to target memory area. Can be
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NULL, but not all such calls might be
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recorded.
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In case of KMEMTRACE_EVENT_ALLOC events, the next fields follow:
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Requested bytes (8 bytes) Total number of requested bytes,
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unsigned, must not be zero.
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Allocated bytes (8 bytes) Total number of actually allocated
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bytes, unsigned, must not be lower
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than requested bytes.
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Requested flags (4 bytes) GFP flags supplied by the caller.
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Target CPU (4 bytes) Signed integer, valid for event id 1.
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If equal to -1, target CPU is the same
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as origin CPU, but the reverse might
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not be true.
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The data is made available in the same endianness the machine has.
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Other event ids and type ids may be defined and added. Other fields may be
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added by increasing event size, but see below for details.
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Every modification to the ABI, including new id definitions, are followed
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by bumping the ABI version by one.
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Adding new data to the packet (features) is done at the end of the mandatory
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data:
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Feature size (2 byte)
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Feature ID (1 byte)
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Feature data (Feature size - 3 bytes)
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Users:
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kmemtrace-user - git://repo.or.cz/kmemtrace-user.git
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