From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8576E1F8BCD; Wed, 26 Mar 2025 18:14:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743012894; cv=none; b=NmQT11jEC9ZPKMhdQwfll5X4NDLuSSbnUruKkYiOpPF0VmOTaGB+UeeVPaE0EDejvWL6zh3AoAFQCuFmVb29/j51+afwcCWpX5nBfxflRbaopHx/PwWY6LOXM5Gd4lXYQW6qesjjf0Klg5ga9Z13G116mGg/IDK7025jtCLSh5E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743012894; c=relaxed/simple; bh=cd7EYHFEFbA7MQbzFPnhq7BpVfRthx6uK+y6bly3n58=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Pj4HL9K3B3VmcFL6FkZ2PYbvuQNuu++RoTZ0Wm2WOW1eCjFm17ywDpyG7SwOqteqr3s1ybI7kbp9vf5LYyVq6rzWUOOjQZzPl/mIbIRQtVzxgG5bx32pxVXQ03qfqB/0Fowhbu4zTYFaFDuGDQj69SfX7Y/0SD/WaOg5nuit/I0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=W7AjiESS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="W7AjiESS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73932C4CEE2; Wed, 26 Mar 2025 18:14:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743012894; bh=cd7EYHFEFbA7MQbzFPnhq7BpVfRthx6uK+y6bly3n58=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=W7AjiESSnKTCkRD23VAAdVgS+p1U9DyzVly9BjXM9Pg1mCZJ7KXNsnNCjpjK+ptrY xTCkvNjtbNGsziQbwCoPZ63NGmlkhREmB5v7bOxa8CJ+g5HLF/sZUu2Dpvk1ws1piB t1NsQmGvMDbYf0kduPS9huNHw2HpiIfw7A1PWBZOokQM6y36bahpGl++gM0nrWQFCq pMgiA/JS89kVjqjgNp4vMeNkDeZXrLyF7WA3khkxDZ6uVpsxZU97zBaOEOEgbx4yZi Ru+uxLhvNNKK6AOGZZYnFoHfymaHSSt4Ijm8VpfHhsHXxFXY0fUVJ0GSW6S0jYeKOQ FNiFwksIrSGSA== Date: Wed, 26 Mar 2025 11:14:51 -0700 From: Namhyung Kim To: Howard Chu Cc: acme@kernel.org, mingo@redhat.com, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, peterz@infradead.org, kan.liang@linux.intel.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] perf doc: Improve perf trace's doc on --force-btf option Message-ID: References: <20250326160416.1725322-1-howardchu95@gmail.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250326160416.1725322-1-howardchu95@gmail.com> Hello, On Wed, Mar 26, 2025 at 09:04:16AM -0700, Howard Chu wrote: > As mentioned by Arnaldo in a past discussion (Link: > https://lore.kernel.org/linux-perf-users/Z2m0pWiQgZNXhvxK@x1/), the > current documentation on --force-btf is vague and inaccurate, this patch > aims to provide a clearer explanation of the option. > > Signed-off-by: Howard Chu > Suggested-by: Arnaldo Carvalho de Melo > --- > tools/perf/Documentation/perf-trace.txt | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/tools/perf/Documentation/perf-trace.txt b/tools/perf/Documentation/perf-trace.txt > index 887dc37773d0..cf2445d2ba3d 100644 > --- a/tools/perf/Documentation/perf-trace.txt > +++ b/tools/perf/Documentation/perf-trace.txt > @@ -246,10 +246,10 @@ the thread executes on the designated CPUs. Default is to monitor all CPUs. > arguments to strings (pid to comm, syscall id to syscall name, etc). > > --force-btf:: > - Use btf_dump to pretty print syscall argument data, instead of using hand-crafted pretty > - printers. This option is intended for testing BTF integration in perf trace. btf_dump-based > - pretty-printing serves as a fallback to hand-crafted pretty printers, as the latter can > - better pretty-print integer flags and struct pointers. > + Use libbpf's btf_dump to pretty print syscall arguments, utilizing only the debug > + information from BTF. This option is intended for testing BTF integration in perf > + trace. Using libbpf is a fallback to perf trace's own prettifiers generated from the > + kernel source, as the latter can better pretty-print integer flags and struct members. "the latter" means our own prettifier, right? Then why do we need the fallback as it's better and always works? Thanks, Namhyung > > PAGEFAULTS > ---------- > -- > 2.45.2 >