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SubjectRe: [PATCH] perf tools: update docs regarding kernel/user space unwinding
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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

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