From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41997C04AA8 for ; Thu, 2 May 2019 07:11:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0558F2085A for ; Thu, 2 May 2019 07:11:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gwoImc0T" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726791AbfEBHLX (ORCPT ); Thu, 2 May 2019 03:11:23 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:43663 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726189AbfEBHLV (ORCPT ); Thu, 2 May 2019 03:11:21 -0400 Received: by mail-pf1-f193.google.com with SMTP id e67so672730pfe.10; Thu, 02 May 2019 00:11:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=24w4jqgdtlrA7O2xMmJS0tVlbeaBr/Rj015fWFSNbZI=; b=gwoImc0Tv48Vw2W0H1VZGBT8gNBq33qMavJQKjOfGV10yevNilFZhGl0gdbiLM9Aji zgMEAShSDYDNdJd0gJKgtPbSmIsaPrLT9M0fvX/1J1KjVDS5j7sWe7XM/9ttxeH8pUOt u40da22XZ3Hz64jTo2aLAJAeX9FZ5izqV9JMK92IgLvFRtMUznQDVbCj+IgV5LfOpORM EsN8/b3m+XWkVhhMV4yyw2tstktspnomNHdoP5/c4FWkLETuL3SWEWuWkf0eLyI6JEqh AKayfnHCsNEKj6TZqog4LPzN+RTkU4IvFQHcXGGVvm2rOt+mePSRINV2vDeDxhyK34Ev 6PBA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=24w4jqgdtlrA7O2xMmJS0tVlbeaBr/Rj015fWFSNbZI=; b=iCQM/lPWUlwxMtIreDBaPlTBWSXeIm1hOwQ9JJYRFbb8a2dfz6k68UOzVjbCwl+mjZ mJcXVZjR6nn/6ntRP//3AZ4eW5ORVloSiqTls43Bbg+SJCnDMSAqPFu5xUnf6FAtkW25 k9ggWFDVpj6MPjlBX2IBldr+wkBIPNc72wEmeO6j7tkg7GIjggbT9+jWaSF9ZA1nzmlW WKr8VvNLTznmyRXXY6VbGeAfFvwwHK01mY6P+AxolmpPuieY09Efe8XpYwPbKRzl2O/E HItIDygoZcIUte4rHvMW+0tefNs7/Kc1EZ5PecvEJsYMivzVm17/+9qmNYKP47bsqas5 evqA== X-Gm-Message-State: APjAAAUvHF3T3dmmAuEYS/1rSIlPiN6IDTrgp88FD15WQsdnl98NXU/a AWSle928rAW5N2tVl/7wv40Dbtp9 X-Google-Smtp-Source: APXvYqyDqayyWGx+CkHDisCCey3/85fmYBPHtLicC/C8zbsIslR/KsAUXOYuQp9DgR9EuhOs0sfSpQ== X-Received: by 2002:a65:5304:: with SMTP id m4mr2367817pgq.281.1556781080345; Thu, 02 May 2019 00:11:20 -0700 (PDT) Received: from laptop.DHCP ([104.238.181.70]) by smtp.gmail.com with ESMTPSA id u24sm4686976pfh.91.2019.05.02.00.11.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 02 May 2019 00:11:19 -0700 (PDT) From: Changbin Du To: corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Changbin Du , Mauro Carvalho Chehab Subject: [PATCH v2 18/27] Documentation: x86: convert orc-unwinder.txt to reST Date: Thu, 2 May 2019 15:06:24 +0800 Message-Id: <20190502070633.9809-19-changbin.du@gmail.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190502070633.9809-1-changbin.du@gmail.com> References: <20190502070633.9809-1-changbin.du@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Reviewed-by: Mauro Carvalho Chehab --- 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 6e3c887a0c3b..453557097743 100644 --- a/Documentation/x86/index.rst +++ b/Documentation/x86/index.rst @@ -14,6 +14,7 @@ x86-specific Documentation 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