Re: [PATCH 7/7] DWARF: add the config option

From: Jiri Kosina
Date: Sat May 06 2017 - 10:25:01 EST

[ adding Josh to CC ]

On Fri, 5 May 2017, Linus Torvalds wrote:

> > The DWARF unwinder is in place and ready. So introduce the config option
> > to allow users to enable it. It is by default off due to missing
> > assembly annotations.
> Who actually ends up using this?

As a datapoint -- we've been using dwarf unwinder in SUSE kernels since
stone age, because we do not enable frame pointer, as it adds up to 10% of
runtime slowdown for certain workloads, but we want reliable stacktraces
so that we can actually debug user reports.

Now that we have nicely reliable stacktraces thanks to Josh's objtool for
FP-enabled builds, we'd like to bring comparably understandable traces
also to non-FP enabled builds.

> Put another way; the last time we did crazy stuff like this, it got
> reverted. For a damn good reason, despite some people being in denial
> about those reasons.

There had been personal issues involved previously, no questions about
that :)


Jiri Kosina