Em Fri, 26 Apr 2019 23:31:41 +0800
Changbin Du <changbin.du@xxxxxxxxx> escreveu:
> This converts the plain text documentation to reStructuredText format and
> add it to Sphinx TOC tree. No essential content change.
>
> Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
> ---
> Documentation/x86/index.rst | 1 +
> .../{orc-unwinder.txt => orc-unwinder.rst} | 27 ++++++++++---------
> 2 files changed, 16 insertions(+), 12 deletions(-)
> rename Documentation/x86/{orc-unwinder.txt => orc-unwinder.rst} (93%)
>
> diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
> index 4e9fa2b046df..c41c17906b6d 100644
> --- a/Documentation/x86/index.rst
> +++ b/Documentation/x86/index.rst
> @@ -14,6 +14,7 @@ Linux x86 Support
> kernel-stacks
> entry_64
> earlyprintk
> + orc-unwinder
> zero-page
> tlb
> mtrr
> diff --git a/Documentation/x86/orc-unwinder.txt b/Documentation/x86/orc-unwinder.rst
> similarity index 93%
> rename from Documentation/x86/orc-unwinder.txt
> rename to Documentation/x86/orc-unwinder.rst
> index cd4b29be29af..d811576c1f3e 100644
> --- a/Documentation/x86/orc-unwinder.txt
> +++ b/Documentation/x86/orc-unwinder.rst
> @@ -1,8 +1,11 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +============
> ORC unwinder
> ============
>
> Overview
> ---------
> +========
>
> The kernel CONFIG_UNWINDER_ORC option enables the ORC unwinder, which is
> similar in concept to a DWARF unwinder. The difference is that the
> @@ -23,12 +26,12 @@ correlate instruction addresses with their stack states at run time.
>
>
> ORC vs frame pointers
> ----------------------
> +=====================
>
> With frame pointers enabled, GCC adds instrumentation code to every
> function in the kernel. The kernel's .text size increases by about
> 3.2%, resulting in a broad kernel-wide slowdown. Measurements by Mel
> -Gorman [1] have shown a slowdown of 5-10% for some workloads.
> +Gorman [1]_ have shown a slowdown of 5-10% for some workloads.
>
> In contrast, the ORC unwinder has no effect on text size or runtime
> performance, because the debuginfo is out of band. So if you disable
> @@ -55,7 +58,7 @@ depending on the kernel config.
>
>
> ORC vs DWARF
> -------------
> +============
>
> ORC debuginfo's advantage over DWARF itself is that it's much simpler.
> It gets rid of the complex DWARF CFI state machine and also gets rid of
> @@ -65,7 +68,7 @@ mission critical oops code.
>
> The simpler debuginfo format also enables the unwinder to be much faster
> than DWARF, which is important for perf and lockdep. In a basic
> -performance test by Jiri Slaby [2], the ORC unwinder was about 20x
> +performance test by Jiri Slaby [2]_, the ORC unwinder was about 20x
> faster than an out-of-tree DWARF unwinder. (Note: That measurement was
> taken before some performance tweaks were added, which doubled
> performance, so the speedup over DWARF may be closer to 40x.)
> @@ -85,7 +88,7 @@ still be able to control the format, e.g. no complex state machines.
>
>
> ORC unwind table generation
> ----------------------------
> +===========================
>
> The ORC data is generated by objtool. With the existing compile-time
> stack metadata validation feature, objtool already follows all code
> @@ -133,7 +136,7 @@ objtool follows GCC code quite well.
>
>
> Unwinder implementation details
> --------------------------------
> +===============================
>
> Objtool generates the ORC data by integrating with the compile-time
> stack metadata validation feature, which is described in detail in
> @@ -154,7 +157,7 @@ subset of the table needs to be searched.
>
>
> Etymology
> ----------
> +=========
>
> Orcs, fearsome creatures of medieval folklore, are the Dwarves' natural
> enemies. Similarly, the ORC unwinder was created in opposition to the
> @@ -162,7 +165,7 @@ complexity and slowness of DWARF.
>
> "Although Orcs rarely consider multiple solutions to a problem, they do
> excel at getting things done because they are creatures of action, not
> -thought." [3] Similarly, unlike the esoteric DWARF unwinder, the
> +thought." [3]_ Similarly, unlike the esoteric DWARF unwinder, the
> veracious ORC unwinder wastes no time or siloconic effort decoding
> variable-length zero-extended unsigned-integer byte-coded
> state-machine-based debug information entries.
> @@ -174,6 +177,6 @@ brutal, unyielding efficiency.
> ORC stands for Oops Rewind Capability.
>
>
> -[1] https://lkml.kernel.org/r/20170602104048.jkkzssljsompjdwy@xxxxxxx
> -[2] https://lkml.kernel.org/r/d2ca5435-6386-29b8-db87-7f227c2b713a@xxxxxxx
> -[3] http://dustin.wikidot.com/half-orcs-and-orcs
> +.. [1] https://lkml.kernel.org/r/20170602104048.jkkzssljsompjdwy@xxxxxxx
> +.. [2] https://lkml.kernel.org/r/d2ca5435-6386-29b8-db87-7f227c2b713a@xxxxxxx
> +.. [3] http://dustin.wikidot.com/half-orcs-and-orcs
Thanks,
Mauro
