From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Clarke Subject: Re: [PATCH] perf tools: update docs regarding kernel/user space unwinding Date: Thu, 26 Mar 2020 16:32:26 -0500 Message-ID: <38ba2caa-dadd-52c4-c6ea-5e01b7e59ee2@us.ibm.com> References: <20200325164053.10177-1-tonyj@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200325164053.10177-1-tonyj@suse.de> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Tony Jones , linux-perf-users@vger.kernel.org Cc: Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org List-Id: linux-perf-users.vger.kernel.org On 3/25/20 11:40 AM, Tony Jones wrote: > The method of unwinding for kernel space is defined by the kernel config, > not by the value of --call-graph. Improve the documentation to reflect > this. > diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt > index 8ead55593984..88cf35fbedc5 100644 > --- a/tools/perf/Documentation/perf-config.txt > +++ b/tools/perf/Documentation/perf-config.txt > @@ -405,14 +405,16 @@ ui.*:: > This option is only applied to TUI. > > call-graph.*:: > - When sub-commands 'top' and 'report' work with -g/—-children > - there're options in control of call-graph. > + The following controls the handling of call-graphs (obtained via the > + -g/--callgraph options). > > call-graph.record-mode:: > - The record-mode can be 'fp' (frame pointer), 'dwarf' and 'lbr'. > - The value of 'dwarf' is effective only if perf detect needed library > - (libunwind or a recent version of libdw). > - 'lbr' only work for cpus that support it. > + The mode for user space can be 'fp' (frame pointer), 'dwarf' > + and 'lbr'. The value 'dwarf' is effective only if libunwind > + (or a recent version of libdw) is present on the system; > + the value 'lbr' only works for certain cpus. The method for > + kernel space is controlled not by this option but by the > + kernel config (CONFIG_UNWINDER_*). Your changes are just copying the old text, so this isn't a criticism of your patches. Do we have information to replace "a recent version of libdw", which will quickly get stale? PC