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SubjectRe: [PATCH 3/3] utrace-based ftrace "process" engine, v2
On Sat, 21 Mar 2009 10:12:35 +0100 Ingo Molnar <mingo@elte.hu> wrote:

>
> * Andrew Morton <akpm@linux-foundation.org> wrote:
>
> > On Sat, 21 Mar 2009 08:43:01 +0100 Ingo Molnar <mingo@elte.hu> wrote:
> >
> > >
> > > * Roland McGrath <roland@redhat.com> wrote:
> > >
> > > > From: Frank Ch. Eigler <fche@redhat.com>
> > > >
> > > > This is v2 of the prototype utrace-ftrace interface. This code is
> > > > based on Roland McGrath's utrace API, which provides programmatic
> > > > hooks to the in-tree tracehook layer. This new patch interfaces
> > > > many of those events to ftrace, as configured by a small number of
> > > > debugfs controls. Here's the
> > > > /debugfs/tracing/process_trace_README:
> > >
> > > Please submit changes/enhancements to kernel/trace/* to the tracing
> > > tree maintainers (Steve and me) for review, testing and integration.
> > >
> > > Please also post patches against the latest tracing tree:
> > >
> > > http://people.redhat.com/mingo/tip.git/README
> >
> > uhm, this patch depends on the (large) utrace patch, which is not
> > kernel/trace material.
>
> The thing is, utrace crashes in Fedora have dominated kerneloops.org
> for many months, so i'm not sure what to make of the idea of posting
> a 4000+ lines of core kernel code patchset on the last day of the
> development cycle, a posting that has carefully avoided the Cc:-ing
> of affected maintainers ;-)
>
> Utrace is very much tracing material - without the ftrace plugin the
> whole utrace machinery is just something that provides a _ton_ of
> hooks to something entirely external: SystemTap mainly.

Roland's changelogs don't mention systemtap at all afacit.

That was, umm, major information lossage.

> kernel/utrace.c should probably be introduced as
> kernel/trace/utrace.c not kernel/utrace.c. It also overlaps pending
> work in the tracing tree and cooperation would be nice and desired.
>
> The ftrace/utrace plugin is the only real connection utrace has to
> the mainline kernel, so proper review by the tracing folks and
> cooperation with the tracing folks is very much needed for the whole
> thing.

Actually it seems that the whole utrace-ftrace thing is a big distraction and
could/should just be omitted. This is a systemtap feature and should be viewed as
such.

This is all a bit weird.


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