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

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Message-ID: <aGVo9b1xiT1Moq-P@google.com>
Date: Wed, 2 Jul 2025 10:14:29 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Sam James <sam@...too.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

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,
Namhyung