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Tue, 23 Apr 2019 09:38:36 -0700 (PDT) Received: from localhost.localdomain ([104.238.181.70]) by smtp.gmail.com with ESMTPSA id v1sm24364801pff.81.2019.04.23.09.38.31 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 23 Apr 2019 09:38:35 -0700 (PDT) From: Changbin Du To: Jonathan Corbet Subject: [PATCH v4 54/63] Documentation: x86: convert orc-unwinder.txt to reST Date: Wed, 24 Apr 2019 00:29:23 +0800 Message-Id: <20190423162932.21428-55-changbin.du@gmail.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190423162932.21428-1-changbin.du@gmail.com> References: <20190423162932.21428-1-changbin.du@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Wed, 24 Apr 2019 05:41:33 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: fenghua.yu@intel.com, mchehab+samsung@kernel.org, linux-doc@vger.kernel.org, linux-pci@vger.kernel.org, linux-gpio@vger.kernel.org, x86@kernel.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, mingo@redhat.com, Bjorn Helgaas , tglx@linutronix.de, linuxppc-dev@lists.ozlabs.org, Changbin Du Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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 --- 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@suse.de -[2] https://lkml.kernel.org/r/d2ca5435-6386-29b8-db87-7f227c2b713a@suse.cz -[3] http://dustin.wikidot.com/half-orcs-and-orcs +.. [1] https://lkml.kernel.org/r/20170602104048.jkkzssljsompjdwy@suse.de +.. [2] https://lkml.kernel.org/r/d2ca5435-6386-29b8-db87-7f227c2b713a@suse.cz +.. [3] http://dustin.wikidot.com/half-orcs-and-orcs -- 2.20.1