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2019-04-02math64: New DIV64_U64_ROUND_CLOSEST helperSimon Horman
Provide DIV64_U64_ROUND_CLOSEST helper which performs division rounded to the closest integer using an unsigned 64bit dividend and divisor. This will be used in a follow-up patch to allow calculation of clock divisors with high frequency parents in the R-Car Gen3 CPG MSSR driver where overflow occurs if either the dividend or divisor is 32bit. Signed-off-by: Simon Horman <horms+renesas@verge.net.au> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
2018-10-26mm: don't miss the last page because of round-off errorRoman Gushchin
I've noticed, that dying memory cgroups are often pinned in memory by a single pagecache page. Even under moderate memory pressure they sometimes stayed in such state for a long time. That looked strange. My investigation showed that the problem is caused by applying the LRU pressure balancing math: scan = div64_u64(scan * fraction[lru], denominator), where denominator = fraction[anon] + fraction[file] + 1. Because fraction[lru] is always less than denominator, if the initial scan size is 1, the result is always 0. This means the last page is not scanned and has no chances to be reclaimed. Fix this by rounding up the result of the division. In practice this change significantly improves the speed of dying cgroups reclaim. [guro@fb.com: prevent double calculation of DIV64_U64_ROUND_UP() arguments] Link: http://lkml.kernel.org/r/20180829213311.GA13501@castle Link: http://lkml.kernel.org/r/20180827162621.30187-3-guro@fb.com Signed-off-by: Roman Gushchin <guro@fb.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Rik van Riel <riel@surriel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-13Merge tag 'docs-4.15' of git://git.lwn.net/linuxLinus Torvalds
Pull documentation updates from Jonathan Corbet: "A relatively calm cycle for the docs tree again. - The old driver statement has been added to the kernel docs. - We have a couple of new helper scripts. find-unused-docs.sh from Sayli Karnic will point out kerneldoc comments that are not actually used in the documentation. Jani Nikula's documentation-file-ref-check finds references to non-existing files. - A new ftrace document from Steve Rostedt. - Vinod Koul converted the dmaengine docs to RST Beyond that, it's mostly simple fixes. This set reaches outside of Documentation/ a bit more than most. In all cases, the changes are to comment docs, mostly from Randy, in places where there didn't seem to be anybody better to take them" * tag 'docs-4.15' of git://git.lwn.net/linux: (52 commits) documentation: fb: update list of available compiled-in fonts MAINTAINERS: update DMAengine documentation location dmaengine: doc: ReSTize pxa_dma doc dmaengine: doc: ReSTize dmatest doc dmaengine: doc: ReSTize client API doc dmaengine: doc: ReSTize provider doc dmaengine: doc: Add ReST style dmaengine document ftrace/docs: Add documentation on how to use ftrace from within the kernel bug-hunting.rst: Fix an example and a typo in a Sphinx tag scripts: Add a script to find unused documentation samples: Convert timers to use timer_setup() documentation: kernel-api: add more info on bitmap functions Documentation: fix selftests related file refs Documentation: fix ref to power basic-pm-debugging Documentation: fix ref to trace stm content Documentation: fix ref to coccinelle content Documentation: fix ref to workqueue content Documentation: fix ref to sphinx/kerneldoc.py Documentation: fix locking rt-mutex doc refs docs: dev-tools: correct Coccinelle version number ...
2017-11-02License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseGreg Kroah-Hartman
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-10-07math64: add missing kernel-doc notationRandy Dunlap
Add missing kernel-doc notation (function parameters) for several div() functions. Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-01-14math64, timers: Fix 32bit mul_u64_u32_shr() and friendsPeter Zijlstra
It turns out that while GCC-4.4 manages to generate 32x32->64 mult instructions for the 32bit mul_u64_u32_shr() code, any GCC after that fails horribly. Fix this by providing an explicit mul_u32_u32() function which can be architcture provided. Reported-by: Chris Metcalf <cmetcalf@mellanox.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Chris Metcalf <cmetcalf@mellanox.com> [for tile] Cc: Christopher S. Hall <christopher.s.hall@intel.com> Cc: David Gibson <david@gibson.dropbear.id.au> Cc: John Stultz <john.stultz@linaro.org> Cc: Laurent Vivier <lvivier@redhat.com> Cc: Liav Rehana <liavr@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Parit Bhargava <prarit@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20161209083011.GD15765@worktop.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-11-10KVM: x86: Replace call-back set_tsc_khz() with a common functionHaozhong Zhang
Both VMX and SVM propagate virtual_tsc_khz in the same way, so this patch removes the call-back set_tsc_khz() and replaces it with a common function. Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-11-10KVM: x86: Add a common TSC scaling functionHaozhong Zhang
VMX and SVM calculate the TSC scaling ratio in a similar logic, so this patch generalizes it to a common TSC scaling function. Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com> [Inline the multiplication and shift steps into mul_u64_u64_shr. Remove BUG_ON. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2013-12-11math64: Add mul_u64_u32_shr()Peter Zijlstra
Introduce mul_u64_u32_shr() as proposed by Andy a while back; it allows using 64x64->128 muls on 64bit archs and recent GCC which defines __SIZEOF_INT128__ and __int128. (This new method will be used by the scheduler.) Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: fweisbec@gmail.com Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/n/tip-hxjoeuzmrcaumR0uZwjpe2pv@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-08-23math64: New separate div64_u64_rem helperMike Snitzer
Commit f792685006274a850e6cc0ea9ade275ccdfc90bc ("math64: New div64_u64_rem helper") implemented div64_u64 in terms of div64_u64_rem. But div64_u64_rem was removed because it slowed down div64_u64 (and there were no other users of div64_u64_rem). Device Mapper's I/O statistics support has a need for div64_u64_rem; reintroduce this helper as a separate method that doesn't slow down div64_u64, especially on 32-bit systems. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2013-06-12include/linux/math64.h: add div64_ul()Alex Shi
There is div64_long() to handle the s64/long division, but no mocro do u64/ul division. It is necessary in some scenarios, so add this function. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Alex Shi <alex.shi@intel.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-04-30Revert "math64: New div64_u64_rem helper"Stanislaw Gruszka
This reverts commit f792685006274a850e6cc0ea9ade275ccdfc90bc. The cputime scaling code was changed/fixed and does not need the div64_u64_rem() primitive anymore. It has no other users, so let's remove them. Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: rostedt@goodmis.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Dave Hansen <dave@sr71.net> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1367314507-9728-4-git-send-email-sgruszka@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-03-13math64: New div64_u64_rem helperFrederic Weisbecker
Provide an extended version of div64_u64() that also returns the remainder of the division. We are going to need this to refine the cputime scaling code. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org>
2012-03-15math: Introduce div64_longSasha Levin
Add a div64_long macro which is used to devide a 64bit number by a long (which can be 4 bytes on 32bit systems and 8 bytes on 64bit systems). Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Cc: johnstul@us.ibm.com Link: http://lkml.kernel.org/r/1331829374-31543-1-git-send-email-levinsasha928@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2010-10-26div64_u64(): improve precision on 32bit platformsBrian Behlendorf
The current implementation of div64_u64 for 32bit systems returns an approximately correct result when the divisor exceeds 32bits. Since doing 64bit division using 32bit hardware is a long since solved problem we just use one of the existing proven methods. Additionally, add a div64_s64 function to correctly handle doing signed 64bit division. Addresses https://bugzilla.redhat.com/show_bug.cgi?id=616105 Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Ben Woodard <bwoodard@llnl.gov> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Mark Grondona <mgrondona@llnl.gov> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-06-12add an inlined version of iter_div_u64_remJeremy Fitzhardinge
iter_div_u64_rem is used in the x86-64 vdso, which cannot call other kernel code. For this case, provide the always_inlined version, __iter_div_u64_rem. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-12common implementation of iterative div/modJeremy Fitzhardinge
We have a few instances of the open-coded iterative div/mod loop, used when we don't expcet the dividend to be much bigger than the divisor. Unfortunately modern gcc's have the tendency to strength "reduce" this into a full mod operation, which isn't necessarily any faster, and even if it were, doesn't exist if gcc implements it in libgcc. The workaround is to put a dummy asm statement in the loop to prevent gcc from performing the transformation. This patch creates a single implementation of this loop, and uses it to replace the open-coded versions I know about. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: john stultz <johnstul@us.ibm.com> Cc: Segher Boessenkool <segher@kernel.crashing.org> Cc: Christian Kujau <lists@nerdbynature.de> Cc: Robert Hancock <hancockr@shaw.ca> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-05-01rename div64_64 to div64_u64Roman Zippel
Rename div64_64 to div64_u64 to make it consistent with the other divide functions, so it clearly includes the type of the divide. Move its definition to math64.h as currently no architecture overrides the generic implementation. They can still override it of course, but the duplicated declarations are avoided. Signed-off-by: Roman Zippel <zippel@linux-m68k.org> Cc: Avi Kivity <avi@qumranet.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: David Howells <dhowells@redhat.com> Cc: Jeff Dike <jdike@addtoit.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: "David S. Miller" <davem@davemloft.net> Cc: Patrick McHardy <kaber@trash.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-05-01introduce explicit signed/unsigned 64bit divideRoman Zippel
The current do_div doesn't explicitly say that it's unsigned and the signed counterpart is missing, which is e.g. needed when dealing with time values. This introduces 64bit signed/unsigned divide functions which also attempts to cleanup the somewhat awkward calling API, which often requires the use of temporary variables for the dividend. To avoid the need for temporary variables everywhere for the remainder, each divide variant also provides a version which doesn't return the remainder. Each architecture can now provide optimized versions of these function, otherwise generic fallback implementations will be used. As an example I provided an alternative for the current x86 divide, which avoids the asm casts and using an union allows gcc to generate better code. It also avoids the upper divde in a few more cases, where the result is known (i.e. upper quotient is zero). Signed-off-by: Roman Zippel <zippel@linux-m68k.org> Cc: john stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>