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
         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: 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>
      b2441318
  2. 26 Jul, 2017 9 commits
    • Dennis Zhou (Facebook)'s avatar
      percpu: skip chunks if the alloc does not fit in the contig hint · 13f96637
      Dennis Zhou (Facebook) authored
      This patch adds chunk->contig_bits_start to keep track of the contig
      hint's offset and the check to skip the chunk if it does not fit. If
      the chunk's contig hint starting offset cannot satisfy an allocation,
      the allocator assumes there is enough memory pressure in this chunk to
      either use a different chunk or create a new one. This accepts a less
      tight packing for a smoother latency curve.
      Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
      Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      13f96637
    • Dennis Zhou (Facebook)'s avatar
      percpu: add first_bit to keep track of the first free in the bitmap · 86b442fb
      Dennis Zhou (Facebook) authored
      This patch adds first_bit to keep track of the first free bit in the
      bitmap. This hint helps prevent scanning of fully allocated blocks.
      Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
      Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      86b442fb
    • Dennis Zhou (Facebook)'s avatar
      percpu: introduce bitmap metadata blocks · ca460b3c
      Dennis Zhou (Facebook) authored
      This patch introduces the bitmap metadata blocks and adds the skeleton
      of the code that will be used to maintain these blocks.  Each chunk's
      bitmap is made up of full metadata blocks. These blocks maintain basic
      metadata to help prevent scanning unnecssarily to update hints. Full
      scanning methods are used for the skeleton and will be replaced in the
      coming patches. A number of helper functions are added as well to do
      conversion of pages to blocks and manage offsets. Comments will be
      updated as the final version of each function is added.
      
      There exists a relationship between PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE,
      the region size, and unit_size. Every chunk's region (including offsets)
      is page aligned at the beginning to preserve alignment. The end is
      aligned to LCM(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE) to ensure that the end
      can fit with the populated page map which is by page and every metadata
      block is fully accounted for. The unit_size is already page aligned, but
      must also be aligned with PCPU_BITMAP_BLOCK_SIZE to ensure full metadata
      blocks.
      Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
      Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      ca460b3c
    • Dennis Zhou (Facebook)'s avatar
      percpu: replace area map allocator with bitmap · 40064aec
      Dennis Zhou (Facebook) authored
      The percpu memory allocator is experiencing scalability issues when
      allocating and freeing large numbers of counters as in BPF.
      Additionally, there is a corner case where iteration is triggered over
      all chunks if the contig_hint is the right size, but wrong alignment.
      
      This patch replaces the area map allocator with a basic bitmap allocator
      implementation. Each subsequent patch will introduce new features and
      replace full scanning functions with faster non-scanning options when
      possible.
      
      Implementation:
      This patchset removes the area map allocator in favor of a bitmap
      allocator backed by metadata blocks. The primary goal is to provide
      consistency in performance and memory footprint with a focus on small
      allocations (< 64 bytes). The bitmap removes the heavy memmove from the
      freeing critical path and provides a consistent memory footprint. The
      metadata blocks provide a bound on the amount of scanning required by
      maintaining a set of hints.
      
      In an effort to make freeing fast, the metadata is updated on the free
      path if the new free area makes a page free, a block free, or spans
      across blocks. This causes the chunk's contig hint to potentially be
      smaller than what it could allocate by up to the smaller of a page or a
      block. If the chunk's contig hint is contained within a block, a check
      occurs and the hint is kept accurate. Metadata is always kept accurate
      on allocation, so there will not be a situation where a chunk has a
      later contig hint than available.
      
      Evaluation:
      I have primarily done testing against a simple workload of allocation of
      1 million objects (2^20) of varying size. Deallocation was done by in
      order, alternating, and in reverse. These numbers were collected after
      rebasing ontop of a80099a1. I present the worst-case numbers here:
      
        Area Map Allocator:
      
              Object Size | Alloc Time (ms) | Free Time (ms)
              ----------------------------------------------
                    4B    |        310      |     4770
                   16B    |        557      |     1325
                   64B    |        436      |      273
                  256B    |        776      |      131
                 1024B    |       3280      |      122
      
        Bitmap Allocator:
      
              Object Size | Alloc Time (ms) | Free Time (ms)
              ----------------------------------------------
                    4B    |        490      |       70
                   16B    |        515      |       75
                   64B    |        610      |       80
                  256B    |        950      |      100
                 1024B    |       3520      |      200
      
      This data demonstrates the inability for the area map allocator to
      handle less than ideal situations. In the best case of reverse
      deallocation, the area map allocator was able to perform within range
      of the bitmap allocator. In the worst case situation, freeing took
      nearly 5 seconds for 1 million 4-byte objects. The bitmap allocator
      dramatically improves the consistency of the free path. The small
      allocations performed nearly identical regardless of the freeing
      pattern.
      
      While it does add to the allocation latency, the allocation scenario
      here is optimal for the area map allocator. The area map allocator runs
      into trouble when it is allocating in chunks where the latter half is
      full. It is difficult to replicate this, so I present a variant where
      the pages are second half filled. Freeing was done sequentially. Below
      are the numbers for this scenario:
      
        Area Map Allocator:
      
              Object Size | Alloc Time (ms) | Free Time (ms)
              ----------------------------------------------
                    4B    |       4118      |     4892
                   16B    |       1651      |     1163
                   64B    |        598      |      285
                  256B    |        771      |      158
                 1024B    |       3034      |      160
      
        Bitmap Allocator:
      
              Object Size | Alloc Time (ms) | Free Time (ms)
              ----------------------------------------------
                    4B    |        481      |       67
                   16B    |        506      |       69
                   64B    |        636      |       75
                  256B    |        892      |       90
                 1024B    |       3262      |      147
      
      The data shows a parabolic curve of performance for the area map
      allocator. This is due to the memmove operation being the dominant cost
      with the lower object sizes as more objects are packed in a chunk and at
      higher object sizes, the traversal of the chunk slots is the dominating
      cost. The bitmap allocator suffers this problem as well. The above data
      shows the inability to scale for the allocation path with the area map
      allocator and that the bitmap allocator demonstrates consistent
      performance in general.
      
      The second problem of additional scanning can result in the area map
      allocator completing in 52 minutes when trying to allocate 1 million
      4-byte objects with 8-byte alignment. The same workload takes
      approximately 16 seconds to complete for the bitmap allocator.
      
      V2:
      Fixed a bug in pcpu_alloc_first_chunk end_offset was setting the bitmap
      using bytes instead of bits.
      
      Added a comment to pcpu_cnt_pop_pages to explain bitmap_weight.
      Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
      Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      40064aec
    • Dennis Zhou (Facebook)'s avatar
      percpu: introduce nr_empty_pop_pages to help empty page accounting · 0cecf50c
      Dennis Zhou (Facebook) authored
      pcpu_nr_empty_pop_pages is used to ensure there are a handful of free
      pages around to serve atomic allocations. A new field, nr_empty_pop_pages,
      is added to the pcpu_chunk struct to keep track of the number of empty
      pages. This field is needed as the number of empty populated pages is
      globally tracked and deltas are used to update in the bitmap allocator.
      Pages that contain a hidden area are not considered to be empty. This
      new field is exposed in percpu_stats.
      Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
      Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      0cecf50c
    • Dennis Zhou (Facebook)'s avatar
      percpu: modify base_addr to be region specific · c0ebfdc3
      Dennis Zhou (Facebook) authored
      Originally, the first chunk was served by one or two chunks, each
      given a region they are responsible for. Despite this, the arithmetic
      was based off of the true base_addr of the chunk making it be overly
      inclusive.
      
      This patch moves the base_addr of chunks that are responsible for the
      first chunk. The base_addr must remain page aligned to keep the
      address alignment correct, so it is the beginning of the region served
      page aligned down. start_offset holds where the region served begins
      from this new base_addr.
      
      The corresponding percpu address checks are modified to be more specific
      as a result. The first chunk considers only the dynamic region and both
      first chunk and reserved chunk checks ignore the static region. The
      static region addresses should never be passed into the allocator. There
      is no impact here besides distinguishing the first chunk and making the
      checks specific.
      
      The percpu pointer to physical address is left intact as addresses are
      not given out in the non-allocated portion of percpu memory.
      
      nr_pages is added to pcpu_chunk to keep track of the size of the entire
      region served containing both start_offset and end_offset. This variable
      will be used to manage the bitmap allocator.
      Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
      Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      c0ebfdc3
    • Dennis Zhou (Facebook)'s avatar
      percpu: end chunk area maps page aligned for the populated bitmap · 6b9d7c8e
      Dennis Zhou (Facebook) authored
      The area map allocator manages the first chunk area by hiding all but
      the region it is responsible for serving in the area map. To align this
      with the populated page bitmap, end_offset is introduced to keep track
      of the delta to end page aligned. The area map is appended with the
      page aligned end when necessary to be in line with how the bitmap
      allocator requires the ending to be aligned with the LCM of PAGE_SIZE
      and the size of each bitmap block. percpu_stats is updated to ignore
      this region when present.
      Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
      Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      6b9d7c8e
    • Dennis Zhou (Facebook)'s avatar
      percpu: remove has_reserved from pcpu_chunk · 4af1e6fb
      Dennis Zhou (Facebook) authored
      Prior this variable was used to manage statistics when the first chunk
      had a reserved region. The previous patch introduced start_offset to
      keep track of the offset by value rather than boolean. Therefore,
      has_reserved can be removed.
      Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
      Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      4af1e6fb
    • Dennis Zhou (Facebook)'s avatar
      percpu: introduce start_offset to pcpu_chunk · e2266705
      Dennis Zhou (Facebook) authored
      The reserved chunk arithmetic uses a global variable
      pcpu_reserved_chunk_limit that is set in the first chunk init code to
      hide a portion of the area map. The bitmap allocator to come will
      eventually move the base_addr up and require both the reserved chunk
      and static chunk to maintain this offset. pcpu_reserved_chunk_limit is
      removed and start_offset is added.
      
      The first chunk that is circulated and is pcpu_first_chunk serves the
      dynamic region, the region following the reserved region. The reserved
      chunk address check will temporarily use the first chunk to identify its
      address range. A following patch will increase the base_addr and remove
      this. If there is no reserved chunk, this will check the static region
      and return false because those values should never be passed into the
      allocator.
      
      Lastly, when linking in the first chunk, make sure to count the right
      free region for the number of empty populated pages.
      Signed-off-by: default avatarDennis Zhou <dennisszhou@gmail.com>
      Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      e2266705
  3. 17 Jul, 2017 1 commit
  4. 21 Jun, 2017 1 commit
    • Dennis Zhou's avatar
      percpu: fix early calls for spinlock in pcpu_stats · 303abfdf
      Dennis Zhou authored
      From 2c06e795162cb306c9707ec51d3e1deadb37f573 Mon Sep 17 00:00:00 2001
      From: Dennis Zhou <dennisz@fb.com>
      Date: Wed, 21 Jun 2017 10:17:09 -0700
      
      Commit 30a5b536 ("percpu: expose statistics about percpu memory via
      debugfs") introduces percpu memory statistics. pcpu_stats_chunk_alloc
      takes the spin lock and disables/enables irqs on creation of a chunk. Irqs
      are not enabled when the first chunk is initialized and thus kernels are
      failing to boot with kernel debugging enabled. Fixed by changing _irq to
      _irqsave and _irqrestore.
      
      Fixes: 30a5b536 ("percpu: expose statistics about percpu memory via debugfs")
      Signed-off-by: default avatarDennis Zhou <dennisz@fb.com>
      Reported-by: default avatarAlexander Levin <alexander.levin@verizon.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      303abfdf
  5. 20 Jun, 2017 2 commits