The Immediate Values are still waiting in the LTTng tree. Actually, I am waiting to see enough tracepoints in the mainline Linux kernel to justify the use of Immediate Values before I re-post them. Otherwise, I seem to be the only one convinced of their use, given the number of tracepoints present in the LTTng kernel tree.
Regarding Mainline, kmemtrace adds enough tracepoints to have a tiny, but measurable, impact on the localhost tbench workload (one would still have to figure out if it's really statistically significant by running more passes than I can given the time I have on my hands). Note that this workload is _very_ heavy on the number of tracepoint sites executed and sensitive to cache-line layout changes.
I won't fight to push them, but if there is sufficient willingness to have them merged, I will consider posting them as a "git pull" request.