1. 02 Nov, 2017 1 commit
    • Greg Kroah-Hartman's avatar
      License cleanup: add SPDX GPL-2.0 license identifier to files with no license · b2441318
      Greg Kroah-Hartman authored
      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
      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: default avatarKate Stewart <kstewart@linuxfoundation.org>
      Reviewed-by: default avatarPhilippe Ombredanne <pombredanne@nexb.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
  2. 02 Mar, 2017 3 commits
  3. 08 Oct, 2016 1 commit
    • Alexey Dobriyan's avatar
      mm: unrig VMA cache hit ratio · 131ddc5c
      Alexey Dobriyan authored
      Current code doesn't count first FIND operation after VMA cache flush
      (which happen surprisingly often) artificially increasing cache hit ratio.
      On my regular setup the difference is:
      		Before				After
      	* boot, login into KDE
      	vmacache_find_calls 446216	vmacache_find_calls 492741
      	vmacache_find_hits 277596	vmacache_find_hits 276096
      		~62.2%				~56.0%
      	* rebuild kernel (no changes to code, usual config)
      	vmacache_find_calls 1943007	vmacache_find_calls 2083718
      	vmacache_find_hits 1246123	vmacache_find_hits 1244146
      		~64.1%				~59.7%
      	* rebuild kernel (full rebuild, usual config)
      	vmacache_find_calls 32163155	vmacache_find_calls 33677183
      	vmacache_find_hits 27889956	vmacache_find_hits 27877591
      		~88.2%				~84.3%
      Total: ~4% cache hit ratio.
      If someone is counting _relative_ cache _miss_ ratio, misreporting is much
      Link: http://lkml.kernel.org/r/20160822225009.GA3934@p183.telecom.bySigned-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
      Cc: Davidlohr Bueso <dave@stgolabs.net>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  4. 06 Nov, 2015 1 commit
  5. 13 Dec, 2014 1 commit
  6. 04 Jun, 2014 2 commits
  7. 28 Apr, 2014 1 commit
    • Linus Torvalds's avatar
      mm: don't pointlessly use BUG_ON() for sanity check · 50f5aa8a
      Linus Torvalds authored
      BUG_ON() is a big hammer, and should be used _only_ if there is some
      major corruption that you cannot possibly recover from, making it
      imperative that the current process (and possibly the whole machine) be
      terminated with extreme prejudice.
      The trivial sanity check in the vmacache code is *not* such a fatal
      error.  Recovering from it is absolutely trivial, and using BUG_ON()
      just makes it harder to debug for no actual advantage.
      To make matters worse, the placement of the BUG_ON() (only if the range
      check matched) actually makes it harder to hit the sanity check to begin
      with, so _if_ there is a bug (and we just got a report from Srivatsa
      Bhat that this can indeed trigger), it is harder to debug not just
      because the machine is possibly dead, but because we don't have better
      BUG_ON() must *die*.  Maybe we should add a checkpatch warning for it,
      because it is simply just about the worst thing you can ever do if you
      hit some "this cannot happen" situation.
      Reported-by: default avatarSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
      Cc: Davidlohr Bueso <davidlohr@hp.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  8. 07 Apr, 2014 1 commit
    • Davidlohr Bueso's avatar
      mm: per-thread vma caching · 615d6e87
      Davidlohr Bueso authored
      This patch is a continuation of efforts trying to optimize find_vma(),
      avoiding potentially expensive rbtree walks to locate a vma upon faults.
      The original approach (https://lkml.org/lkml/2013/11/1/410), where the
      largest vma was also cached, ended up being too specific and random,
      thus further comparison with other approaches were needed.  There are
      two things to consider when dealing with this, the cache hit rate and
      the latency of find_vma().  Improving the hit-rate does not necessarily
      translate in finding the vma any faster, as the overhead of any fancy
      caching schemes can be too high to consider.
      We currently cache the last used vma for the whole address space, which
      provides a nice optimization, reducing the total cycles in find_vma() by
      up to 250%, for workloads with good locality.  On the other hand, this
      simple scheme is pretty much useless for workloads with poor locality.
      Analyzing ebizzy runs shows that, no matter how many threads are
      running, the mmap_cache hit rate is less than 2%, and in many situations
      below 1%.
      The proposed approach is to replace this scheme with a small per-thread
      cache, maximizing hit rates at a very low maintenance cost.
      Invalidations are performed by simply bumping up a 32-bit sequence
      number.  The only expensive operation is in the rare case of a seq
      number overflow, where all caches that share the same address space are
      flushed.  Upon a miss, the proposed replacement policy is based on the
      page number that contains the virtual address in question.  Concretely,
      the following results are seen on an 80 core, 8 socket x86-64 box:
      1) System bootup: Most programs are single threaded, so the per-thread
         scheme does improve ~50% hit rate by just adding a few more slots to
         the cache.
      | caching scheme | hit-rate | cycles (billion) |
      | baseline       | 50.61%   | 19.90            |
      | patched        | 73.45%   | 13.58            |
      2) Kernel build: This one is already pretty good with the current
         approach as we're dealing with good locality.
      | caching scheme | hit-rate | cycles (billion) |
      | baseline       | 75.28%   | 11.03            |
      | patched        | 88.09%   | 9.31             |
      3) Oracle 11g Data Mining (4k pages): Similar to the kernel build workload.
      | caching scheme | hit-rate | cycles (billion) |
      | baseline       | 70.66%   | 17.14            |
      | patched        | 91.15%   | 12.57            |
      4) Ebizzy: There's a fair amount of variation from run to run, but this
         approach always shows nearly perfect hit rates, while baseline is just
         about non-existent.  The amounts of cycles can fluctuate between
         anywhere from ~60 to ~116 for the baseline scheme, but this approach
         reduces it considerably.  For instance, with 80 threads:
      | caching scheme | hit-rate | cycles (billion) |
      | baseline       | 1.06%    | 91.54            |
      | patched        | 99.97%   | 14.18            |
      [akpm@linux-foundation.org: fix nommu build, per Davidlohr]
      [akpm@linux-foundation.org: document vmacache_valid() logic]
      [akpm@linux-foundation.org: attempt to untangle header files]
      [akpm@linux-foundation.org: add vmacache_find() BUG_ON]
      [hughd@google.com: add vmacache_valid_mm() (from Oleg)]
      [akpm@linux-foundation.org: coding-style fixes]
      [akpm@linux-foundation.org: adjust and enhance comments]
      Signed-off-by: default avatarDavidlohr Bueso <davidlohr@hp.com>
      Reviewed-by: default avatarRik van Riel <riel@redhat.com>
      Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Reviewed-by: default avatarMichel Lespinasse <walken@google.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Tested-by: default avatarHugh Dickins <hughd@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>