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>
---
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
--
2.20.1
