Update README

[lttng-modules.git] / README

diff --git a/README b/README
index 583d0e024864d2e37fd22a86d847ec955539b1d7..1fd49b68dea49d650b394c064a4c43f73a5bbabe 100644 (file)
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+++ b/README
@@ -1,7 +1,7 @@
 LTTng 2.0 modules
 
 Mathieu Desnoyers
 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:
 
 LTTng 2.0 kernel modules build against a vanilla or distribution kernel, without
 need for additional patches. Other features:


@@ -9,7 +9,7 @@ need for additional patches. Other features:
 - Produces CTF (Common Trace Format) natively,
   (http://www.efficios.com/ctf)
 - Tracepoints, Function tracer, CPU Performance Monitoring Unit (PMU)
 - Produces CTF (Common Trace Format) natively,
   (http://www.efficios.com/ctf)
 - Tracepoints, Function tracer, CPU Performance Monitoring Unit (PMU)

-  counters and kprobes support,
+  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 PMU counter, pid, ppid, tid, comm name, etc).
 - Integrated interface for both kernel and userspace tracing,
 - Have the ability to attach "context" information to events in the
   trace (e.g. any PMU counter, pid, ppid, tid, comm name, etc).


@@ -22,21 +22,20 @@ 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
 
 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

+# 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
 
 
 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
 

-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 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
 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


@@ -46,3 +45,14 @@ 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.
 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.