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Date: Mon, 21 Oct 2019 09:20:28 -0300
From: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Clark Williams <williams@...hat.com>,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
Adrian Hunter <adrian.hunter@...el.com>,
Andi Kleen <ak@...ux.intel.com>,
"Gustavo A . R . Silva" <gustavo@...eddedor.com>,
Thomas Richter <tmricht@...ux.ibm.com>,
Yunfeng Ye <yeyunfeng@...wei.com>,
Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [GIT PULL] perf/urgent fixes
Em Mon, Oct 21, 2019 at 08:23:54AM +0200, Ingo Molnar escreveu:
> * Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> > Please consider pulling,
<SNIP>
> > tools/perf/util/header.c | 4 +++-
> > tools/perf/util/util.c | 6 ++++--
> > 12 files changed, 65 insertions(+), 17 deletions(-)
> Pulled, thanks a lot Arnaldo!
Thanks!
> A minor bugreport:
> There's a new nuisance message that I noticed when 'perf top' is started:
> a "vmlinux file has not been found" - with a "press any key" - but the
> message doesn't actually wait for the keypress, it's cleared on the first
> screen refresh...
I'll investigate the problems reported after pushing out the current
perf/core lot, thanks for the detailed report!
- Arnaldo
> I'd argue that both the keypress action and the warning message is
> superfluous:
>
> - It annoys users while not actually giving any straightforward way to
> fix it. It's displayed on every startup of perf top, which is highly
> distracting.
>
> - At least on Ubuntu it appears to be wrong, because the vmlinux is
> available and symbol resolution/annotation appears to be working fine:
>
> # uname -a
> Linux dagon 5.4.0-rc3-custom-00557-gb6c81ae120e0 #1 SMP PREEMPT Sun Oct 20 15:28:00 CEST 2019 x86_64 x86_64 x86_64 GNU/Linux
>
> # dpkg -l | grep gb6c81ae120e
> ii linux-headers-5.4.0-rc3-custom-00557-gb6c81ae120e0 5.4.0-rc3-custom-00557-gb6c81ae120e0-1 amd64 Linux kernel headers for 5.4.0-rc3-custom-00557-gb6c81ae120e0 on amd64
> ii linux-image-5.4.0-rc3-custom-00557-gb6c81ae120e0 5.4.0-rc3-custom-00557-gb6c81ae120e0-1 amd64 Linux kernel, version 5.4.0-rc3-custom-00557-gb6c81ae120e0
> ii linux-image-5.4.0-rc3-custom-00557-gb6c81ae120e0-dbg 5.4.0-rc3-custom-00557-gb6c81ae120e0-1 amd64 Linux kernel debugging symbols for 5.4.0-rc3-custom-00557-gb6c81ae120e0
> ii linux-libc-dev:amd64 5.4.0-rc3-custom-00557-gb6c81ae120e0-1 amd64 Linux support headers for userspace development
>
> Note that the 'dbg' package is installed which includes the vmlinux,
> and perf does seem to find it:
>
> # dpkg-query -L linux-image-5.4.0-rc3-custom-00557-gb6c81ae120e0-dbg | grep vmlinux$
> /usr/lib/debug/lib/modules/5.4.0-rc3-custom-00557-gb6c81ae120e0/vmlinux
>
> I can see annotated kernel functions just fine.
>
> - Finally, when I run perf as root then kallsyms and /proc/kcore is used
> to annotate the kernel. So the 'cannot resolve' message cannot even be
> true. :-)
>
> Instead I believe some sort of explanation should be printed in the
> natural flow when there's an unknown symbol or someone tries to enter a
> kernel symbol that cannot be further resolved. Even there it probably
> shouldn't be a 'warning' message, but something printed in-line where
> usually we'd see the annotated output - to disrupt the normal workflow as
> little as possible.
>
> Secondly, there also appears to be a TUI weirdness when the annotated
> kernel functions are small (or weird): the blue cursor is stuck at the
> top and I cannot move between the annotated instructions with the down/up
> arrow:
>
> Samples: 13M of event 'cycles', 4000 Hz, Event count (approx.): 1272420588851
> clear_page_rep /usr/lib/debug/boot/vmlinux-5.4.0-rc3-custom-00557-gb6c81ae120e0 [Percent: local period]
> 0.01 │ mov $0x200,%ecx ▒
> │ xorl %eax,%eax ▒
> 0.01 │ xor %eax,%eax ▒
> │ rep stosq ▒
> 99.27 │ rep stos %rax,%es:(%rdi) ▒
> │ ret ▒
> 0.71 │ ← retq
>
> I can still exit the screen with 'q', and can move around in larger
> annotated kernel functions. Not sure whether it's related to function
> size, or perhaps to the 'hottest' instruction that the cursor is normally
> placed at.
>
> Thanks,
>
> Ingo
--
- Arnaldo
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