X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=README;h=f4e3368cec50bad0d3f88465d565193617d6abf5;hb=edb5c2da83545004c5f556accb79d010a6b1e3a9;hp=e6a0d4a043d85611117b90440af27e757137c29b;hpb=6b40862968f9211983918d0e99cbe3656a0dd600;p=lttng-modules.git

diff --git a/README b/README
index e6a0d4a0..f4e3368c 100644
--- a/README
+++ b/README
@@ -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).
@@ -22,12 +22,14 @@ 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
@@ -37,9 +39,19 @@ 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 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.
+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.
+
+* 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.