linux-kernel - Re: [PATCH v13 00/18] unwind_deferred: Implement sframe handling

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Message-ID: <20260205135411.5fb22df2@gandalf.local.home>
Date: Thu, 5 Feb 2026 13:54:11 -0500
From: Steven Rostedt <rostedt@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Jens Remus <jremus@...ux.ibm.com>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org, x86@...nel.org,
 linux-mm@...ck.org, Josh Poimboeuf <jpoimboe@...nel.org>, Masami Hiramatsu
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 <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>
Subject: Re: [PATCH v13 00/18] unwind_deferred: Implement sframe handling

On Thu, 5 Feb 2026 10:26:10 -0800
Namhyung Kim <namhyung@...nel.org> wrote:

> > Namhyung Kim's related perf tools deferred callchain support can be used
> > for testing ("perf record --call-graph fp,defer" and "perf report/script").  
> 
> Is it possible for users to choose the unwinder - frame pointer or
> SFrame at runtime?  I feel like the option should be
> "--call-graph sframe,defer" or just "--call-graph sframe" if it always
> uses deferred unwinding.

Currently no, and I'm not sure we want that do we? The idea is to use the
best option that is available. Why use frame pointers if sframe is
available and it's being called with defer?

If there's no defer, then sframes are not available, so it defaults to the
best option available (which will likely be frame pointers).

-- Steve