linux-kernel - Re: [PATCH v11 00/14] unwind_user: x86: Deferred unwinding infrastructure

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Message-ID: <87plehkjnb.fsf@gentoo.org>
Date: Thu, 03 Jul 2025 05:01:12 +0100
From: Sam James <sam@...too.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,  fweimer@...hat.com,
  akpm@...ux-foundation.org,  andrii@...nel.org,  axboe@...nel.dk,
  beaub@...ux.microsoft.com,  bpf@...r.kernel.org,  indu.bhagat@...cle.com,
  jemarch@....org,  jolsa@...nel.org,  jpoimboe@...nel.org,
  jremus@...ux.ibm.com,  linux-kernel@...r.kernel.org,
  linux-trace-kernel@...r.kernel.org,  mathieu.desnoyers@...icios.com,
  mhiramat@...nel.org,  mingo@...nel.org,  peterz@...radead.org,
  tglx@...utronix.de,  torvalds@...ux-foundation.org,  x86@...nel.org
Subject: Re: [PATCH v11 00/14] unwind_user: x86: Deferred unwinding
 infrastructure

Namhyung Kim <namhyung@...nel.org> writes:

> On Wed, Jul 02, 2025 at 12:15:02PM -0400, Steven Rostedt wrote:
>> On Wed, 02 Jul 2025 12:44:51 +0100
>> Sam James <sam@...too.org> wrote:
>> 
>> > In one of the commit messages in the perf series, Steven also gave
>> > `perf record -g -vv true` which was convenient for making sure it's
>> > correctly discovered deferred unwinding support.
>> 
>> Although I posted the patch, the command "perf record -g -vv true" was
>> Namhyung's idea. Just wanted to give credit where credit was due.
>
> Yep, it's to check if perf tool ask the deferred callchain to the
> kernel.  To check if the kernel returns the callchain properly is:
>
>   $ perf report -D | grep -A5 CALLCHAIN_DEFERRED

Thanks both. I'll update my notes and tinker more.

>
> Thanks,
> Namhyung

sam