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author | Ingo Molnar <mingo@elte.hu> | 2010-06-09 18:55:20 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2010-06-09 18:55:57 +0200 |
commit | c726b61c6a5acc54c55ed7a0e7638cc4c5a100a8 (patch) | |
tree | 3f44aa013d31d34951e9610e79ff14c1148ad6ac /Documentation | |
parent | 7be7923633a142402266d642ccebf74f556a649b (diff) | |
parent | 018378c55b03f88ff513aba4e0e93b8d4a9cf241 (diff) | |
download | op-kernel-dev-c726b61c6a5acc54c55ed7a0e7638cc4c5a100a8.zip op-kernel-dev-c726b61c6a5acc54c55ed7a0e7638cc4c5a100a8.tar.gz |
Merge branch 'perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing into perf/core
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/ABI/testing/debugfs-kmemtrace | 71 | ||||
-rw-r--r-- | Documentation/trace/kmemtrace.txt | 126 |
2 files changed, 0 insertions, 197 deletions
diff --git a/Documentation/ABI/testing/debugfs-kmemtrace b/Documentation/ABI/testing/debugfs-kmemtrace deleted file mode 100644 index 5e6a92a..0000000 --- a/Documentation/ABI/testing/debugfs-kmemtrace +++ /dev/null @@ -1,71 +0,0 @@ -What: /sys/kernel/debug/kmemtrace/ -Date: July 2008 -Contact: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro> -Description: - -In kmemtrace-enabled kernels, the following files are created: - -/sys/kernel/debug/kmemtrace/ - cpu<n> (0400) Per-CPU tracing data, see below. (binary) - total_overruns (0400) Total number of bytes which were dropped from - cpu<n> files because of full buffer condition, - non-binary. (text) - abi_version (0400) Kernel's kmemtrace ABI version. (text) - -Each per-CPU file should be read according to the relay interface. That is, -the reader should set affinity to that specific CPU and, as currently done by -the userspace application (though there are other methods), use poll() with -an infinite timeout before every read(). Otherwise, erroneous data may be -read. The binary data has the following _core_ format: - - Event ID (1 byte) Unsigned integer, one of: - 0 - represents an allocation (KMEMTRACE_EVENT_ALLOC) - 1 - represents a freeing of previously allocated memory - (KMEMTRACE_EVENT_FREE) - Type ID (1 byte) Unsigned integer, one of: - 0 - this is a kmalloc() / kfree() - 1 - this is a kmem_cache_alloc() / kmem_cache_free() - 2 - this is a __get_free_pages() et al. - Event size (2 bytes) Unsigned integer representing the - size of this event. Used to extend - kmemtrace. Discard the bytes you - don't know about. - Sequence number (4 bytes) Signed integer used to reorder data - logged on SMP machines. Wraparound - must be taken into account, although - it is unlikely. - Caller address (8 bytes) Return address to the caller. - Pointer to mem (8 bytes) Pointer to target memory area. Can be - NULL, but not all such calls might be - recorded. - -In case of KMEMTRACE_EVENT_ALLOC events, the next fields follow: - - Requested bytes (8 bytes) Total number of requested bytes, - unsigned, must not be zero. - Allocated bytes (8 bytes) Total number of actually allocated - bytes, unsigned, must not be lower - than requested bytes. - Requested flags (4 bytes) GFP flags supplied by the caller. - Target CPU (4 bytes) Signed integer, valid for event id 1. - If equal to -1, target CPU is the same - as origin CPU, but the reverse might - not be true. - -The data is made available in the same endianness the machine has. - -Other event ids and type ids may be defined and added. Other fields may be -added by increasing event size, but see below for details. -Every modification to the ABI, including new id definitions, are followed -by bumping the ABI version by one. - -Adding new data to the packet (features) is done at the end of the mandatory -data: - Feature size (2 byte) - Feature ID (1 byte) - Feature data (Feature size - 3 bytes) - - -Users: - kmemtrace-user - git://repo.or.cz/kmemtrace-user.git - diff --git a/Documentation/trace/kmemtrace.txt b/Documentation/trace/kmemtrace.txt deleted file mode 100644 index 6308735..0000000 --- a/Documentation/trace/kmemtrace.txt +++ /dev/null @@ -1,126 +0,0 @@ - kmemtrace - Kernel Memory Tracer - - by Eduard - Gabriel Munteanu - <eduard.munteanu@linux360.ro> - -I. Introduction -=============== - -kmemtrace helps kernel developers figure out two things: -1) how different allocators (SLAB, SLUB etc.) perform -2) how kernel code allocates memory and how much - -To do this, we trace every allocation and export information to the userspace -through the relay interface. We export things such as the number of requested -bytes, the number of bytes actually allocated (i.e. including internal -fragmentation), whether this is a slab allocation or a plain kmalloc() and so -on. - -The actual analysis is performed by a userspace tool (see section III for -details on where to get it from). It logs the data exported by the kernel, -processes it and (as of writing this) can provide the following information: -- the total amount of memory allocated and fragmentation per call-site -- the amount of memory allocated and fragmentation per allocation -- total memory allocated and fragmentation in the collected dataset -- number of cross-CPU allocation and frees (makes sense in NUMA environments) - -Moreover, it can potentially find inconsistent and erroneous behavior in -kernel code, such as using slab free functions on kmalloc'ed memory or -allocating less memory than requested (but not truly failed allocations). - -kmemtrace also makes provisions for tracing on some arch and analysing the -data on another. - -II. Design and goals -==================== - -kmemtrace was designed to handle rather large amounts of data. Thus, it uses -the relay interface to export whatever is logged to userspace, which then -stores it. Analysis and reporting is done asynchronously, that is, after the -data is collected and stored. By design, it allows one to log and analyse -on different machines and different arches. - -As of writing this, the ABI is not considered stable, though it might not -change much. However, no guarantees are made about compatibility yet. When -deemed stable, the ABI should still allow easy extension while maintaining -backward compatibility. This is described further in Documentation/ABI. - -Summary of design goals: - - allow logging and analysis to be done across different machines - - be fast and anticipate usage in high-load environments (*) - - be reasonably extensible - - make it possible for GNU/Linux distributions to have kmemtrace - included in their repositories - -(*) - one of the reasons Pekka Enberg's original userspace data analysis - tool's code was rewritten from Perl to C (although this is more than a - simple conversion) - - -III. Quick usage guide -====================== - -1) Get a kernel that supports kmemtrace and build it accordingly (i.e. enable -CONFIG_KMEMTRACE). - -2) Get the userspace tool and build it: -$ git clone git://repo.or.cz/kmemtrace-user.git # current repository -$ cd kmemtrace-user/ -$ ./autogen.sh -$ ./configure -$ make - -3) Boot the kmemtrace-enabled kernel if you haven't, preferably in the -'single' runlevel (so that relay buffers don't fill up easily), and run -kmemtrace: -# '$' does not mean user, but root here. -$ mount -t debugfs none /sys/kernel/debug -$ mount -t proc none /proc -$ cd path/to/kmemtrace-user/ -$ ./kmemtraced -Wait a bit, then stop it with CTRL+C. -$ cat /sys/kernel/debug/kmemtrace/total_overruns # Check if we didn't - # overrun, should - # be zero. -$ (Optionally) [Run kmemtrace_check separately on each cpu[0-9]*.out file to - check its correctness] -$ ./kmemtrace-report - -Now you should have a nice and short summary of how the allocator performs. - -IV. FAQ and known issues -======================== - -Q: 'cat /sys/kernel/debug/kmemtrace/total_overruns' is non-zero, how do I fix -this? Should I worry? -A: If it's non-zero, this affects kmemtrace's accuracy, depending on how -large the number is. You can fix it by supplying a higher -'kmemtrace.subbufs=N' kernel parameter. ---- - -Q: kmemtrace_check reports errors, how do I fix this? Should I worry? -A: This is a bug and should be reported. It can occur for a variety of -reasons: - - possible bugs in relay code - - possible misuse of relay by kmemtrace - - timestamps being collected unorderly -Or you may fix it yourself and send us a patch. ---- - -Q: kmemtrace_report shows many errors, how do I fix this? Should I worry? -A: This is a known issue and I'm working on it. These might be true errors -in kernel code, which may have inconsistent behavior (e.g. allocating memory -with kmem_cache_alloc() and freeing it with kfree()). Pekka Enberg pointed -out this behavior may work with SLAB, but may fail with other allocators. - -It may also be due to lack of tracing in some unusual allocator functions. - -We don't want bug reports regarding this issue yet. ---- - -V. See also -=========== - -Documentation/kernel-parameters.txt -Documentation/ABI/testing/debugfs-kmemtrace - |