X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=README;h=3bd0d153a7eacbe48e0b4dc25701a107e8153b06;hb=9d7d747f10bab16b3d85915a5b87e10acd2374f0;hp=583d0e024864d2e37fd22a86d847ec955539b1d7;hpb=3da843ea85c6dd4aef5703fa24ca8bb29d172b57;p=lttng-modules.git

diff --git a/README b/README
index 583d0e02..3bd0d153 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).
@@ -46,3 +46,10 @@ 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.