LTTng 2.0 modules
Mathieu Desnoyers
-July 19, 2011
+February 8, 2012
LTTng 2.0 kernel modules build against a vanilla or distribution kernel, without
need for additional patches. Other features:
- Produces CTF (Common Trace Format) natively,
(http://www.efficios.com/ctf)
-- Function tracer, perf counters and kprobes support,
+- Tracepoints, Function tracer, CPU Performance Monitoring Unit (PMU)
+ counters, kprobes, and kretprobes support,
- Integrated interface for both kernel and userspace tracing,
- Have the ability to attach "context" information to events in the
- trace (e.g. any perf counter, pid, ppid, tid, comm name, etc). So
- basically, all the perf "required fields" like "preempt count" and
- "bkl count" are all optional, specified on a per-tracing-session basis
- (except for timestamp and event id, which are mandatory).
+ trace (e.g. any PMU counter, pid, ppid, tid, comm name, etc).
+ All the extra information fields to be collected with events are
+ optional, specified on a per-tracing-session basis (except for
+ timestamp and event id, which are mandatory).
To build and install, you will need to have your kernel headers available (or
access to your full kernel source tree), and use:
-make
-make modules_install
+% make
+# make modules_install
+# depmod -a
If you need to specify the target directory to the kernel you want to build
against, use:
-KERNELDIR=path_to_kernel_dir make
-KERNELDIR=path_to_kernel_dir make modules_install
-
-Use lttng-tools (git://git.lttng.org/lttng-tools.git) to control the tracer.
-LTTng tools should automatically load the kernel modules when needed.
-
-Use Babeltrace (git://git.efficios.com/babeltrace.git) to print traces as a
-human-readable text log.
-
-Please note that the LTTng-UST 2.0 (user-space tracing counterpart of LTTng 2.0)
-is still in active development and not released yet.
-
-So far, it has been tested on vanilla kernels 2.6.38 and 2.6.39 (on x86 at the
-moment). It should work fine with newer kernels and other architectures, but
-expect build issues with kernels older than 2.6.36. The clock source currently
-used is the standard gettimeofday (slower, less scalable and less precise than
-the LTTng 0.x clocks). Support for LTTng 0.x clocks will be added back soon into
-LTTng 2.0.
+% KERNELDIR=path_to_kernel_dir make
+# KERNELDIR=path_to_kernel_dir make modules_install
+# depmod -a kernel_version
+
+Use lttng-tools to control the tracer. LTTng tools should automatically load
+the kernel modules when needed. Use Babeltrace to print traces as a
+human-readable text log. These tools are available at the following URL:
+http://lttng.org/lttng2.0
+
+So far, it has been tested on vanilla Linux kernels 2.6.38, 2.6.39 and 3.0 (on
+x86 32/64-bit, and powerpc 32-bit at the moment, build tested on ARM). It should
+work fine with newer kernels and other architectures, but expect build issues
+with kernels older than 2.6.36. The clock source currently used is the standard
+gettimeofday (slower, less scalable and less precise than the LTTng 0.x clocks).
+Support for LTTng 0.x clocks will be added back soon into LTTng 2.0. Please
+note that lttng-modules 2.0 can build on a Linux kernel patched with the LTTng
+0.x patchset, but the lttng-modules 2.0 replace the lttng-modules 0.x, so both
+tracers cannot be installed at the same time for a given kernel version.
+
+LTTng-modules depends on having kallsyms enabled in the kernel it is
+built against. Ideally, if you want to have system call tracing, the
+"Trace Syscalls" feature should be enabled too.
+
+* Note about Perf PMU counters support
+
+Each PMU counter has its zero value set when it is attached to a context with
+add-context. Therefore, it is normal that the same counters attached to both the
+stream context and event context show different values for a given event; what
+matters is that they increment at the same rate.
projects / lttng-modules.git / blobdiff