|author||Li Zefan <email@example.com>||2010-05-26 17:22:17 +0800|
|committer||Frederic Weisbecker <firstname.lastname@example.org>||2010-06-09 17:31:22 +0200|
tracing: Remove kmemtrace ftrace plugin
We have been resisting new ftrace plugins and removing existing ones, and kmemtrace has been superseded by kmem trace events and perf-kmem, so we remove it. Signed-off-by: Li Zefan <email@example.com> Acked-by: Pekka Enberg <firstname.lastname@example.org> Acked-by: Eduard - Gabriel Munteanu <email@example.com> Cc: Ingo Molnar <firstname.lastname@example.org> Cc: Steven Rostedt <email@example.com> [ remove kmemtrace from the makefile, handle slob too ] Signed-off-by: Frederic Weisbecker <firstname.lastname@example.org>
Diffstat (limited to 'Documentation/trace')
1 files changed, 0 insertions, 126 deletions
diff --git a/Documentation/trace/kmemtrace.txt b/Documentation/trace/kmemtrace.txt
deleted file mode 100644
@@ -1,126 +0,0 @@
- kmemtrace - Kernel Memory Tracer
- by Eduard - Gabriel Munteanu
-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
-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
-2) Get the userspace tool and build it:
-$ git clone git://repo.or.cz/kmemtrace-user.git # current repository
-$ cd kmemtrace-user/
-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
-# '$' does not mean user, but root here.
-$ mount -t debugfs none /sys/kernel/debug
-$ mount -t proc none /proc
-$ cd path/to/kmemtrace-user/
-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]
-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
- - 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