X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=README;h=1fd49b68dea49d650b394c064a4c43f73a5bbabe;hb=0ec73ddce557ac36a2782a726ab5a00663c2e50d;hp=97c96f6305336366c39f064d150af101bbd8cae8;hpb=14a8117ffda897ab50e9cbe5d3c1e1d34fcb9f2d;p=lttng-modules.git

diff --git a/README b/README
index 97c96f63..1fd49b68 100644
--- a/README
+++ b/README
@@ -1,7 +1,7 @@
 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:
@@ -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)
-  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).
@@ -22,27 +22,37 @@ access to your full kernel source tree), and use:
 
 % 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
+# 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
 
-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-rc7
-(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. 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.
+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.