Messages in this thread |  | | | Subject | Re: [RFC][PATCH 1/5] [PATCH 1/5] events: Add EVENT_FS the event filesystem | | From | Steven Rostedt <> | | Date | Wed, 17 Nov 2010 10:16:59 -0500 |
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On Wed, 2010-11-17 at 16:03 +0100, Ingo Molnar wrote: > * Steven Rostedt <rostedt@goodmis.org> wrote: > > > Are these events now going to be labeled as stable? Is every tracepoint we have, > > much have the same data? Linus specifically said at Kernel Summit that he wants > > absolutely NO modules to have a stable tracepoint. > > I think you are worrying about the wrong things. > > I think Arjan's complaints at the KS stemmed from prior sporadic declarations on > lkml that there is no tracepoint ABI _at all_, and that powertop/latencytop could > break anytime. > > But in reality i strongly disagree with such declarations, and tracepoint data that > is used by PowerTop/timechart/latencytop or perf is and was an ABI, simple as that - > and i've been enforcing that for two years. (We have so few good instrumentation > tools that we _really_ dont want to break them.) > > At that point, realizing that we have an ABI for existing tools, i think it's > fundamentally misguided to go out on a limb trying to put barriers in the way of > other tools that do not even exist to begin with ... > > Our real problem with tracing is lack of relevance, lack of utility, lack of > punch-through analytical power. > > Trying to create a sandbox to _reduce utility_ is like the last step, and a really > optional step, when we have such variety that we want some control over it. It's > always expensive, it always reduces the tool space as collateral damage. > > So please dont think of sysfs or eventfs as a tool to restrict. Think of it as a > tool to _organize_. > > Again, i'd _LOVE_ to have the 'problem' of us having so many tools that analyze > application and kernel behavior in such a rich way that they use tracepoints that > were not supposed to be 'stable'. > > I simply dont see the 'problem' that is being solved here. We had a stable ABI and > we didnt break sysprof or powertop/latencytop in the past and wont break it in the > future either.
What about a tool that picks up tracepoints that were only used by a developer for in-field debugging, and then that tracepoint disappears because of a design change. Is it OK for that tool to break with it?
Do all tools that use tracepoints require a "check" feature?
I guess the problem is that creators of the tools to analyze the kernel have no idea of what they can count on and what they can't. Do we need a process to have these tool creators request to developers to "keep this tracepoint"?
-- Steve
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