|| ||Ingo Molnar <mingo-AT-elte.hu> |
|| ||Linus Torvalds <torvalds-AT-linux-foundation.org> |
|| ||Re: Fix powerTOP regression with 2.6.39-rc5 |
|| ||Sat, 7 May 2011 08:58:03 +0200|
|| ||Steven Rostedt <rostedt-AT-goodmis.org>,
Arjan van de Ven <arjan-AT-linux.intel.com>,
Frederic Weisbecker <fweisbec-AT-gmail.com>,
Peter Zijlstra <a.p.zijlstra-AT-chello.nl>,
Thomas Gleixner <tglx-AT-linutronix.de>|
|| ||Article, Thread
* Linus Torvalds <firstname.lastname@example.org> wrote:
> On Fri, May 6, 2011 at 1:20 PM, Steven Rostedt <email@example.com> wrote:
> > I strongly NACK this!
> Doesn't matter.
> Binary compatibility is more important.
Yes, absolutely, violently agreed.
Acked-by: Ingo Molnar <firstname.lastname@example.org>
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
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?
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