From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: perf not capturing stack traces
Date: Mon, 26 Jan 2015 12:16:21 +0000 [thread overview]
Message-ID: <20150126121621.GG15598@arm.com> (raw)
In-Reply-To: <20150126121243.GA16629@kernel.org>
On Mon, Jan 26, 2015 at 12:12:43PM +0000, Arnaldo Carvalho de Melo wrote:
> Em Mon, Jan 26, 2015 at 10:27:11AM +0000, Will Deacon escreveu:
> > On Sun, Jan 25, 2015 at 03:56:52PM +0000, Russell King - ARM Linux wrote:
> > > On Sat, Jan 24, 2015 at 04:23:42PM -0600, Felipe Balbi wrote:
> > > > yeah, I'll try a few older kernels, also see if I can reproduce on other
> > > > boards.
> > >
> > > Perf works for me with CONFIG_FRAME_POINTER=y, but that's only for kernel
> > > space, and for userspace where the programs have been built for ARM mode
> > > with frame pointers.
> > >
> > > The kernel may work without CONFIG_FRAME_POINTER set, but I've never
> > > tested that, and I'd suggest that (given my experience looking at oops
> > > dumps) it's not all that reliable.
> > >
> > > Lastly, userspace without frame pointers is pretty much hopeless.
> >
> > FWIW, perf can now use libunwind for unwinding the userspace side of
> > things, so it's not quite as bad as it used to be. For the kernel side,
> > if the unwinder isn't working properly it would be nice to know *why*,
> > but I agree that it tends to be far flakier than the frame-pointer method.
>
> Any idea why, with userspace using frame pointers, perf doesn't go all
> the way from kernel to userspace main() (or whatever is the endpoint),
> as Russel stated?
Did he state that? I thought he was just saying that he couldn't unwind
userspace when *not* using frame pointers, which requires you to link
a recent perf with a bleeding-edge libunwind.
Will
next prev parent reply other threads:[~2015-01-26 12:16 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-23 19:51 perf not capturing stack traces Felipe Balbi
2015-01-23 19:53 ` Felipe Balbi
2015-01-23 20:59 ` Arnaldo Carvalho de Melo
2015-01-23 22:37 ` Felipe Balbi
2015-01-24 15:12 ` Arnaldo Carvalho de Melo
2015-01-24 22:23 ` Felipe Balbi
2015-01-25 15:56 ` Russell King - ARM Linux
2015-01-26 10:27 ` Will Deacon
2015-01-26 12:12 ` Arnaldo Carvalho de Melo
2015-01-26 12:16 ` Will Deacon [this message]
2015-01-26 12:29 ` Arnaldo Carvalho de Melo
2015-01-26 13:54 ` Russell King - ARM Linux
2015-01-26 14:33 ` Arnaldo Carvalho de Melo
2015-01-26 13:51 ` Russell King - ARM Linux
2015-01-26 14:37 ` Arnaldo Carvalho de Melo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20150126121621.GG15598@arm.com \
--to=will.deacon@arm$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox