Messages in this thread | | | Date | Sat, 7 May 2011 08:58:03 +0200 | From | Ingo Molnar <> | Subject | Re: Fix powerTOP regression with 2.6.39-rc5 |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Fri, May 6, 2011 at 1:20 PM, Steven Rostedt <rostedt@goodmis.org> wrote: > > > > I strongly NACK this! > > Doesn't matter. > > Binary compatibility is more important.
Yes, absolutely, violently agreed.
Acked-by: Ingo Molnar <mingo@elte.hu>
Steve, we had this argument again and again internally, and you still do not seem to understand it: viable tooling is *way* more important than the short-term, marginal cleanliness interests of kernel developers. We wont be able to merge ftrace into perf until you understand this principle ...
Arjan, Steve, i think we need to create a 'perf test' testcase for ftrace events as well, to catch such ABI breakages faster, hm? It took a couple of months for this breakage to surface and that's clearly too slow.
> And if binaries don't use the interface to parse the format (or just parse it > wrongly - see the fairly recent example of adding uuid's to > /proc/self/mountinfo), then it's a regression. > > And regressions get reverted, unless there are security issues or similar > that makes us go "Oh Gods, we really have to break things". > > I don't understand why this simple logic is so hard for some kernel > developers to understand. Reality matters. Your personal wishes matter NOT AT > ALL.
You have just summed up the main philosophical difference between perf and ftrace: with perf we have a "sane tooling first" approach, while ftrace is still the old "kernel developers first" approach.
In the past 10 years i pushed tons of instrumentation code upstream and for a long time the kernel-integrated ftrace approach looked like the technical best solution to me, but after 2 years of sane instrumentation tooling via a proper user-space ABI and tools/perf/ i'm not looking back.
I am strongly convinced that we need to bite the bullet and unify the two approaches to enable even better tooling: expose the remaining bits of tracing functionality not available via perf yet via the perf ABI and move it under a single umbrella, slowly phase out the ABI-unstable /debug/tracing/ debugfs crap for new features and use the strict perf ABI approach. Steve?
Thanks,
Ingo
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