On Thu, 2009-11-26 at 09:40 +0100, Ingo Molnar wrote: > * Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > I would like to hear what others think about this change before we go > > ahead and implement it. > > You mean TRACE_EVENT() -> DEFINE_SINGLE_EVENT()? Sure, we want todo it > in a more quiet moment of the kernel cycle, not now. > > (TRACE_EVENT_TEMPLATE OTOH has existed for just a few days so it's not a > problem.) Yes the template name is new, I'm not talking about that on particularly. > > > A lot of developers have just learned about TRACE_EVENT and now it > > just disappeared. Well, not really, but in the sense of ' find > > linux.git -name '*.[ch]' | xargs grep TRACE_EVENT' it no longer > > exists. > > A second problem with the TRACE_EVENT name is that it's not just for > tracing - we dont necessarily 'trace' events here. We can use the event > callbacks to collect pure counts: Then we might as well rename the "trace_*" all over the kernel. > > | aldebaran> perf stat -e sched:sched_wakeup ./hackbench 10 > | Time: 0.093 > | > | Performance counter stats for './hackbench 10': > | > | 15481 sched:sched_wakeup > | > | 0.107390574 seconds time elapsed > > etc. Right, because it hooked into a trace_point. > > A third problem is that the name 'TRACE_EVENT' does not tell us what is > being done. Do we declare it? Do we also define it? That's exactly the point. It does both. I actually tried to avoid the "DEFINE/DECLARE" because it becomes confusing to what it does. The TRACE_EVENT macros are obviously unique in the kernel. There are "DECLARE_*" and "DEFINE_*" all over the kernel. And they have an obvious meaning. DECLARE_* is used to set up a declaration for a header. DEFINE_* creates the instance. But TRACE_EVENT will default declare event, but when CREATE_TRACE_POINTS is set, it defines the instances. Oh we should rename that to CREATE_EVENTS? > > DEFINE_SINGLE_EVENT() solves all these problems: > > - It's obvious what it does > > - It suggests users of it that there's another non-single-event > facility, gently nudging them towards the use of the more efficient > DEFINE_EVENT_CLASS() + DEFINE_EVENT() method. > > - It fits nicely into the rest of the naming scheme. Like I said earlier, I'm not really attached to the name. Except that there's already a lot of documentation (I've given tutorials about it) using the TRACE_EVENT name. But who am I to decide? -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|