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. 10 Jul, 2017 1 commit
  3. 06 Jul, 2017 1 commit
    • Huang Ying's avatar
      mm, THP, swap: delay splitting THP during swap out · 38d8b4e6
      Huang Ying authored
      Patch series "THP swap: Delay splitting THP during swapping out", v11.
      This patchset is to optimize the performance of Transparent Huge Page
      (THP) swap.
      Recently, the performance of the storage devices improved so fast that
      we cannot saturate the disk bandwidth with single logical CPU when do
      page swap out even on a high-end server machine.  Because the
      performance of the storage device improved faster than that of single
      logical CPU.  And it seems that the trend will not change in the near
      future.  On the other hand, the THP becomes more and more popular
      because of increased memory size.  So it becomes necessary to optimize
      THP swap performance.
      The advantages of the THP swap support include:
       - Batch the swap operations for the THP to reduce lock
         acquiring/releasing, including allocating/freeing the swap space,
         adding/deleting to/from the swap cache, and writing/reading the swap
         space, etc. This will help improve the performance of the THP swap.
       - The THP swap space read/write will be 2M sequential IO. It is
         particularly helpful for the swap read, which are usually 4k random
         IO. This will improve the performance of the THP swap too.
       - It will help the memory fragmentation, especially when the THP is
         heavily used by the applications. The 2M continuous pages will be
         free up after THP swapping out.
       - It will improve the THP utilization on the system with the swap
         turned on. Because the speed for khugepaged to collapse the normal
         pages into the THP is quite slow. After the THP is split during the
         swapping out, it will take quite long time for the normal pages to
         collapse back into the THP after being swapped in. The high THP
         utilization helps the efficiency of the page based memory management
      There are some concerns regarding THP swap in, mainly because possible
      enlarged read/write IO size (for swap in/out) may put more overhead on
      the storage device.  To deal with that, the THP swap in should be turned
      on only when necessary.  For example, it can be selected via
      "always/never/madvise" logic, to be turned on globally, turned off
      globally, or turned on only for VMA with MADV_HUGEPAGE, etc.
      This patchset is the first step for the THP swap support.  The plan is
      to delay splitting THP step by step, finally avoid splitting THP during
      the THP swapping out and swap out/in the THP as a whole.
      As the first step, in this patchset, the splitting huge page is delayed
      from almost the first step of swapping out to after allocating the swap
      space for the THP and adding the THP into the swap cache.  This will
      reduce lock acquiring/releasing for the locks used for the swap cache
      With the patchset, the swap out throughput improves 15.5% (from about
      3.73GB/s to about 4.31GB/s) in the vm-scalability swap-w-seq test case
      with 8 processes.  The test is done on a Xeon E5 v3 system.  The swap
      device used is a RAM simulated PMEM (persistent memory) device.  To test
      the sequential swapping out, the test case creates 8 processes, which
      sequentially allocate and write to the anonymous pages until the RAM and
      part of the swap device is used up.
      This patch (of 5):
      In this patch, splitting huge page is delayed from almost the first step
      of swapping out to after allocating the swap space for the THP
      (Transparent Huge Page) and adding the THP into the swap cache.  This
      will batch the corresponding operation, thus improve THP swap out
      This is the first step for the THP swap optimization.  The plan is to
      delay splitting the THP step by step and avoid splitting the THP
      In this patch, one swap cluster is used to hold the contents of each THP
      swapped out.  So, the size of the swap cluster is changed to that of the
      THP (Transparent Huge Page) on x86_64 architecture (512).  For other
      architectures which want such THP swap optimization,
      ARCH_USES_THP_SWAP_CLUSTER needs to be selected in the Kconfig file for
      the architecture.  In effect, this will enlarge swap cluster size by 2
      times on x86_64.  Which may make it harder to find a free cluster when
      the swap space becomes fragmented.  So that, this may reduce the
      continuous swap space allocation and sequential write in theory.  The
      performance test in 0day shows no regressions caused by this.
      In the future of THP swap optimization, some information of the swapped
      out THP (such as compound map count) will be recorded in the
      swap_cluster_info data structure.
      The mem cgroup swap accounting functions are enhanced to support charge
      or uncharge a swap cluster backing a THP as a whole.
      The swap cluster allocate/free functions are added to allocate/free a
      swap cluster for a THP.  A fair simple algorithm is used for swap
      cluster allocation, that is, only the first swap device in priority list
      will be tried to allocate the swap cluster.  The function will fail if
      the trying is not successful, and the caller will fallback to allocate a
      single swap slot instead.  This works good enough for normal cases.  If
      the difference of the number of the free swap clusters among multiple
      swap devices is significant, it is possible that some THPs are split
      earlier than necessary.  For example, this could be caused by big size
      difference among multiple swap devices.
      The swap cache functions is enhanced to support add/delete THP to/from
      the swap cache as a set of (HPAGE_PMD_NR) sub-pages.  This may be
      enhanced in the future with multi-order radix tree.  But because we will
      split the THP soon during swapping out, that optimization doesn't make
      much sense for this first step.
      The THP splitting functions are enhanced to support to split THP in swap
      cache during swapping out.  The page lock will be held during allocating
      the swap cluster, adding the THP into the swap cache and splitting the
      THP.  So in the code path other than swapping out, if the THP need to be
      split, the PageSwapCache(THP) will be always false.
      The swap cluster is only available for SSD, so the THP swap optimization
      in this patchset has no effect for HDD.
      [ying.huang@intel.com: fix two issues in THP optimize patch]
        Link: http://lkml.kernel.org/r/87k25ed8zo.fsf@yhuang-dev.intel.com
      [hannes@cmpxchg.org: extensive cleanups and simplifications, reduce code size]
      Link: http://lkml.kernel.org/r/20170515112522.32457-2-ying.huang@intel.comSigned-off-by: default avatar"Huang, Ying" <ying.huang@intel.com>
      Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Suggested-by: Andrew Morton <akpm@linux-foundation.org> [for config option]
      Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> [for changes in huge_memory.c and huge_mm.h]
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@kernel.org>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Shaohua Li <shli@kernel.org>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  4. 09 May, 2017 1 commit
    • Huang Ying's avatar
      mm, swap: use kvzalloc to allocate some swap data structures · 54f180d3
      Huang Ying authored
      Now vzalloc() is used in swap code to allocate various data structures,
      such as swap cache, swap slots cache, cluster info, etc.  Because the
      size may be too large on some system, so that normal kzalloc() may fail.
      But using kzalloc() has some advantages, for example, less memory
      fragmentation, less TLB pressure, etc.  So change the data structure
      allocation in swap code to use kvzalloc() which will try kzalloc()
      firstly, and fallback to vzalloc() if kzalloc() failed.
      In general, although kmalloc() will reduce the number of high-order
      pages in short term, vmalloc() will cause more pain for memory
      fragmentation in the long term.  And the swap data structure allocation
      that is changed in this patch is expected to be long term allocation.
      From Dave Hansen:
       "for example, we have a two-page data structure. vmalloc() takes two
        effectively random order-0 pages, probably from two different 2M pages
        and pins them. That "kills" two 2M pages. kmalloc(), allocating two
        *contiguous* pages, will not cross a 2M boundary. That means it will
        only "kill" the possibility of a single 2M page. More 2M pages == less
      The allocation in this patch occurs during swap on time, which is
      usually done during system boot, so usually we have high opportunity to
      allocate the contiguous pages successfully.
      The allocation for swap_map[] in struct swap_info_struct is not changed,
      because that is usually quite large and vmalloc_to_page() is used for
      it.  That makes it a little harder to change.
      Link: http://lkml.kernel.org/r/20170407064911.25447-1-ying.huang@intel.comSigned-off-by: default avatarHuang Ying <ying.huang@intel.com>
      Acked-by: default avatarTim Chen <tim.c.chen@intel.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarRik van Riel <riel@redhat.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Shaohua Li <shli@kernel.org>
      Cc: Minchan Kim <minchan@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  5. 03 May, 2017 1 commit
  6. 21 Mar, 2017 1 commit
    • Huang Ying's avatar
      mm, swap: Remove WARN_ON_ONCE() in free_swap_slot() · 093b995e
      Huang Ying authored
      Before commit 452b94b8 ("mm/swap: don't BUG_ON() due to
      uninitialized swap slot cache"), the following bug is reported,
        ------------[ cut here ]------------
        kernel BUG at mm/swap_slots.c:270!
        invalid opcode: 0000 [#1] SMP
        CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb #1
        Hardware name: System manufacturer System Product Name/Z170-K, BIOS 1803 05/06/2016
        RIP: 0010:free_swap_slot+0xba/0xd0
        Call Trace:
        ---[ end trace aefc9ede53e0ab21 ]---
      This is raised by the BUG_ON(!swap_slot_cache_initialized) in
      free_swap_slot().  This is incorrect, because even if the swap slots
      cache fails to be initialized, the swap should operate properly without
      the swap slots cache.  And the use_swap_slot_cache check later in the
      function will protect the uninitialized swap slots cache case.
      In commit 452b94b8, the BUG_ON() is replaced by WARN_ON_ONCE().  In
      the patch, the WARN_ON_ONCE() is removed too.
      Reported-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Acked-by: default avatarTim Chen <tim.c.chen@linux.intel.com>
      Cc: Michal Hocko <mhocko@suse.com>
      Signed-off-by: default avatar"Huang, Ying" <ying.huang@intel.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  7. 20 Mar, 2017 1 commit
    • Linus Torvalds's avatar
      mm/swap: don't BUG_ON() due to uninitialized swap slot cache · 452b94b8
      Linus Torvalds authored
      This BUG_ON() triggered for me once at shutdown, and I don't see a
      reason for the check.  The code correctly checks whether the swap slot
      cache is usable or not, so an uninitialized swap slot cache is not
      actually problematic afaik.
      I've temporarily just switched the BUG_ON() to a WARN_ON_ONCE(), since
      I'm not sure why that seemingly pointless check was there.  I suspect
      the real fix is to just remove it entirely, but for now we'll warn about
      it but not bring the machine down.
      Cc: "Huang, Ying" <ying.huang@intel.com>
      Cc: Tim Chen <tim.c.chen@linux.intel.com>
      Cc: Michal Hocko <mhocko@suse.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  8. 23 Feb, 2017 2 commits
    • Huang Ying's avatar
      mm/swap: skip readahead only when swap slot cache is enabled · ba81f838
      Huang Ying authored
      Because during swap off, a swap entry may have swap_map[] ==
      SWAP_HAS_CACHE (for example, just allocated).  If we return NULL in
      __read_swap_cache_async(), the swap off will abort.  So when swap slot
      cache is disabled, (for swap off), we will wait for page to be put into
      swap cache in such race condition.  This should not be a problem for swap
      slot cache, because swap slot cache should be drained after clearing
      [ying.huang@intel.com: fix memory leak in __read_swap_cache_async()]
        Link: http://lkml.kernel.org/r/874lzt6znd.fsf@yhuang-dev.intel.com
      Link: http://lkml.kernel.org/r/5e2c5f6abe8e6eb0797408897b1bba80938e9b9d.1484082593.git.tim.c.chen@linux.intel.comSigned-off-by: default avatar"Huang, Ying" <ying.huang@intel.com>
      Signed-off-by: default avatarTim Chen <tim.c.chen@linux.intel.com>
      Cc: Aaron Lu <aaron.lu@intel.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Christian Borntraeger <borntraeger@de.ibm.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
      Cc: Huang Ying <ying.huang@intel.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Jonathan Corbet <corbet@lwn.net> escreveu:
      Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Michal Hocko <mhocko@kernel.org>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Shaohua Li <shli@kernel.org>
      Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Tim Chen's avatar
      mm/swap: add cache for swap slots allocation · 67afa38e
      Tim Chen authored
      We add per cpu caches for swap slots that can be allocated and freed
      quickly without the need to touch the swap info lock.
      Two separate caches are maintained for swap slots allocated and swap
      slots returned.  This is to allow the swap slots to be returned to the
      global pool in a batch so they will have a chance to be coaelesced with
      other slots in a cluster.  We do not reuse the slots that are returned
      right away, as it may increase fragmentation of the slots.
      The swap allocation cache is protected by a mutex as we may sleep when
      searching for empty slots in cache.  The swap free cache is protected by
      a spin lock as we cannot sleep in the free path.
      We refill the swap slots cache when we run out of slots, and we disable
      the swap slots cache and drain the slots if the global number of slots
      fall below a low watermark threshold.  We re-enable the cache agian when
      the slots available are above a high watermark.
      [ying.huang@intel.com: use raw_cpu_ptr over this_cpu_ptr for swap slots access]
      [tim.c.chen@linux.intel.com: add comments on locks in swap_slots.h]
        Link: http://lkml.kernel.org/r/20170118180327.GA24225@linux.intel.com
      Link: http://lkml.kernel.org/r/35de301a4eaa8daa2977de6e987f2c154385eb66.1484082593.git.tim.c.chen@linux.intel.comSigned-off-by: default avatarTim Chen <tim.c.chen@linux.intel.com>
      Signed-off-by: default avatar"Huang, Ying" <ying.huang@intel.com>
      Reviewed-by: default avatarMichal Hocko <mhocko@suse.com>
      Cc: Aaron Lu <aaron.lu@intel.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Christian Borntraeger <borntraeger@de.ibm.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
      Cc: Huang Ying <ying.huang@intel.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Jonathan Corbet <corbet@lwn.net> escreveu:
      Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Shaohua Li <shli@kernel.org>
      Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>