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SubjectRe: [PATCH 3/3] utrace-based ftrace "process" engine, v2
On Sat, 21 Mar 2009 07:51:41 -0400 "Frank Ch. Eigler" <fche@redhat.com> wrote:

> Hi -
>
> On Sat, Mar 21, 2009 at 04:19:54AM -0700, Andrew Morton wrote:
> > [...]
> > > 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.
>
> There have been many mixed messages from LKML on the topic - sometimes
> mentioning systemtap is forbidden, other times necessary. Sorry about
> that.

heh. We all love systemtap and want it to get better.

> There are several non-systemtap clients in existence or under
> development. You've may have heard of the ptrace cleanup, a
> multi-client ptrace replacement, an on-the-fly core dumper, the ftrace
> widget, user-space probes. All of these should have somewhat
> compelling non-systemtap uses, if that's an important criterion.

Well I dunno. You guys are closer to this than I am, but I'd have thought
that systemtap is the main game here, and most/all of the above is just
fluff.

IOW, "this helps systemtap" is sufficient reason for merging a kernel
change. For sufficiently large values of "help", and sufficiently small
values of "eww", of course.



I have strong memories of being traumatised by reading the uprobes code.
What's the story on all of that nowadays?


>
> > 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. [...]
>
> utrace is a better way to perform user thread management than what is
> there now, and the utrace-ftrace widget shows how to *hook* thread
> events such as syscalls in a lighter weight / more managed way than
> the first one proposed. (That's one reason we've been participating
> in the ftrace discussions.) Of course it can be made to use the fine
> syscall pretty-printing code recently added.

eh. Boring. Let's fix systemtap?


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