-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.
+
+* Kernel config options required
+
+CONFIG_MODULES: required
+ * Kernel modules support.
+CONFIG_KALLSYMS: required
+ * See wrapper/ files. This is necessary until the few required missing
+ symbols are exported to GPL modules from mainline.
+CONFIG_HIGH_RES_TIMERS: required
+ * Needed for LTTng 2.x clock source.
+CONFIG_TRACEPOINTS: required
+ kernel tracepoint instrumentation
+ * Enabled as side-effect of any of the perf/ftrace/blktrace
+ instrumentation features.
+
+
+* Kernel config options supported (optional)
+
+The following kernel configuration options will affect the features
+available from LTTng:
+
+
+CONFIG_HAVE_SYSCALL_TRACEPOINTS:
+ system call tracing
+ lttng enable-event -k --syscall
+ lttng enable-event -k -a
+CONFIG_PERF_EVENTS:
+ performance counters
+ lttng add-context -t perf:*
+CONFIG_EVENT_TRACING:
+ needed to allow block layer tracing
+CONFIG_KPROBES:
+ Dynamic probe.
+ lttng enable-event -k --probe ...
+CONFIG_KRETPROBES:
+ Dynamic function entry/return probe.
+ lttng enable-event -k --function ...
+
+
+* 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.