1. 13 Dec, 2016 1 commit
  2. 27 Aug, 2016 1 commit
  3. 26 Jul, 2016 1 commit
    • Michal Hocko's avatar
      mm, memcg: use consistent gfp flags during readahead · 8a5c743e
      Michal Hocko authored
      Vladimir has noticed that we might declare memcg oom even during
      readahead because read_pages only uses GFP_KERNEL (with mapping_gfp
      restriction) while __do_page_cache_readahead uses
      page_cache_alloc_readahead which adds __GFP_NORETRY to prevent from
      OOMs.  This gfp mask discrepancy is really unfortunate and easily
      fixable.  Drop page_cache_alloc_readahead() which only has one user and
      outsource the gfp_mask logic into readahead_gfp_mask and propagate this
      mask from __do_page_cache_readahead down to read_pages.
      This alone would have only very limited impact as most filesystems are
      implementing ->readpages and the common implementation mpage_readpages
      does GFP_KERNEL (with mapping_gfp restriction) again.  We can tell it to
      use readahead_gfp_mask instead as this function is called only during
      readahead as well.  The same applies to read_cache_pages.
      ext4 has its own ext4_mpage_readpages but the path which has pages !=
      NULL can use the same gfp mask.  Btrfs, cifs, f2fs and orangefs are
      doing a very similar pattern to mpage_readpages so the same can be
      applied to them as well.
      [akpm@linux-foundation.org: coding-style fixes]
      [mhocko@suse.com: restrict gfp mask in mpage_alloc]
        Link: http://lkml.kernel.org/r/20160610074223.GC32285@dhcp22.suse.cz
      Link: http://lkml.kernel.org/r/1465301556-26431-1-git-send-email-mhocko@kernel.orgSigned-off-by: default avatarMichal Hocko <mhocko@suse.com>
      Cc: Vladimir Davydov <vdavydov@parallels.com>
      Cc: Chris Mason <clm@fb.com>
      Cc: Steve French <sfrench@samba.org>
      Cc: Theodore Ts'o <tytso@mit.edu>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Mike Marshall <hubcap@omnibond.com>
      Cc: Jaegeuk Kim <jaegeuk@kernel.org>
      Cc: Changman Lee <cm224.lee@samsung.com>
      Cc: Chao Yu <yuchao0@huawei.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  4. 04 Apr, 2016 1 commit
    • Kirill A. Shutemov's avatar
      mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros · 09cbfeaf
      Kirill A. Shutemov authored
      PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time
      ago with promise that one day it will be possible to implement page
      cache with bigger chunks than PAGE_SIZE.
      This promise never materialized.  And unlikely will.
      We have many places where PAGE_CACHE_SIZE assumed to be equal to
      PAGE_SIZE.  And it's constant source of confusion on whether
      PAGE_CACHE_* or PAGE_* constant should be used in a particular case,
      especially on the border between fs and mm.
      Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
      breakage to be doable.
      Let's stop pretending that pages in page cache are special.  They are
      The changes are pretty straight-forward:
       - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;
       - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;
       - page_cache_get() -> get_page();
       - page_cache_release() -> put_page();
      This patch contains automated changes generated with coccinelle using
      script below.  For some reason, coccinelle doesn't patch header files.
      I've called spatch for them manually.
      The only adjustment after coccinelle is revert of changes to
      PAGE_CAHCE_ALIGN definition: we are going to drop it later.
      There are few places in the code where coccinelle didn't reach.  I'll
      fix them manually in a separate patch.  Comments and documentation also
      will be addressed with the separate patch.
      virtual patch
      expression E;
      + E
      expression E;
      + E
      + PAGE_SHIFT
      + PAGE_SIZE
      + PAGE_MASK
      expression E;
      + PAGE_ALIGN(E)
      expression E;
      - page_cache_get(E)
      + get_page(E)
      expression E;
      - page_cache_release(E)
      + put_page(E)
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  5. 15 Jan, 2016 2 commits
  6. 07 Nov, 2015 1 commit
  7. 06 Nov, 2015 1 commit
    • Roman Gushchin's avatar
      mm: use only per-device readahead limit · 600e19af
      Roman Gushchin authored
      Maximal readahead size is limited now by two values:
       1) by global 2Mb constant (MAX_READAHEAD in max_sane_readahead())
       2) by configurable per-device value* (bdi->ra_pages)
      There are devices, which require custom readahead limit.
      For instance, for RAIDs it's calculated as number of devices
      multiplied by chunk size times 2.
      Readahead size can never be larger than bdi->ra_pages * 2 value
      (POSIX_FADV_SEQUNTIAL doubles readahead size).
      If so, why do we need two limits?
      I suggest to completely remove this max_sane_readahead() stuff and
      use per-device readahead limit everywhere.
      Also, using right readahead size for RAID disks can significantly
      increase i/o performance:
        dd if=/dev/md2 of=/dev/null bs=100M count=100
        100+0 records in
        100+0 records out
        10485760000 bytes (10 GB) copied, 12.9741 s, 808 MB/s
        $ dd if=/dev/md2 of=/dev/null bs=100M count=100
        100+0 records in
        100+0 records out
        10485760000 bytes (10 GB) copied, 8.91317 s, 1.2 GB/s
      (It's an 8-disks RAID5 storage).
      This patch doesn't change sys_readahead and madvise(MADV_WILLNEED)
      behavior introduced by 6d2be915 ("mm/readahead.c: fix readahead
      failure for memoryless NUMA nodes and limit readahead pages").
      Signed-off-by: default avatarRoman Gushchin <klamm@yandex-team.ru>
      Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: onstantin Khlebnikov <khlebnikov@yandex-team.ru>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  8. 16 Oct, 2015 1 commit
    • Michal Hocko's avatar
      mm, fs: obey gfp_mapping for add_to_page_cache() · 063d99b4
      Michal Hocko authored
      Commit 6afdb859 ("mm: do not ignore mapping_gfp_mask in page cache
      allocation paths") has caught some users of hardcoded GFP_KERNEL used in
      the page cache allocation paths.  This, however, wasn't complete and
      there were others which went unnoticed.
      Dave Chinner has reported the following deadlock for xfs on loop device:
      : With the recent merge of the loop device changes, I'm now seeing
      : XFS deadlock on my single CPU, 1GB RAM VM running xfs/073.
      : The deadlocked is as follows:
      : kloopd1: loop_queue_read_work
      :       xfs_file_iter_read
      :       lock XFS inode XFS_IOLOCK_SHARED (on image file)
      :       page cache read (GFP_KERNEL)
      :       radix tree alloc
      :       memory reclaim
      :       reclaim XFS inodes
      :       log force to unpin inodes
      :       <wait for log IO completion>
      : xfs-cil/loop1: <does log force IO work>
      :       xlog_cil_push
      :       xlog_write
      :       <loop issuing log writes>
      :               xlog_state_get_iclog_space()
      :               <blocks due to all log buffers under write io>
      :               <waits for IO completion>
      : kloopd1: loop_queue_write_work
      :       xfs_file_write_iter
      :       lock XFS inode XFS_IOLOCK_EXCL (on image file)
      :       <wait for inode to be unlocked>
      : i.e. the kloopd, with it's split read and write work queues, has
      : introduced a dependency through memory reclaim. i.e. that writes
      : need to be able to progress for reads make progress.
      : The problem, fundamentally, is that mpage_readpages() does a
      : GFP_KERNEL allocation, rather than paying attention to the inode's
      : mapping gfp mask, which is set to GFP_NOFS.
      : The didn't used to happen, because the loop device used to issue
      : reads through the splice path and that does:
      :       error = add_to_page_cache_lru(page, mapping, index,
      :                       GFP_KERNEL & mapping_gfp_mask(mapping));
      This has changed by commit aa4d8616 ("block: loop: switch to VFS
      This patch changes mpage_readpage{s} to follow gfp mask set for the
      mapping.  There are, however, other places which are doing basically the
      lustre:ll_dir_filler is doing GFP_KERNEL from the function which
      apparently uses GFP_NOFS for other allocations so let's make this
      cifs:readpages_get_pages is called from cifs_readpages and
      __cifs_readpages_from_fscache called from the same path obeys mapping
      ramfs_nommu_expand_for_mapping is hardcoding GFP_KERNEL as well
      regardless it uses mapping_gfp_mask for the page allocation.
      ext4_mpage_readpages is the called from the page cache allocation path
      same as read_pages and read_cache_pages
      As I've noticed in my previous post I cannot say I would be happy about
      sprinkling mapping_gfp_mask all over the place and it sounds like we
      should drop gfp_mask argument altogether and use it internally in
      __add_to_page_cache_locked that would require all the filesystems to use
      mapping gfp consistently which I am not sure is the case here.  From a
      quick glance it seems that some file system use it all the time while
      others are selective.
      Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
      Reported-by: default avatarDave Chinner <david@fromorbit.com>
      Cc: "Theodore Ts'o" <tytso@mit.edu>
      Cc: Ming Lei <ming.lei@canonical.com>
      Cc: Andreas Dilger <andreas.dilger@intel.com>
      Cc: Oleg Drokin <oleg.drokin@intel.com>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Christoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  9. 02 Jun, 2015 1 commit
    • Tejun Heo's avatar
      writeback: implement and use inode_congested() · 703c2708
      Tejun Heo authored
      In several places, bdi_congested() and its wrappers are used to
      determine whether more IOs should be issued.  With cgroup writeback
      support, this question can't be answered solely based on the bdi
      (backing_dev_info).  It's dependent on whether the filesystem and bdi
      support cgroup writeback and the blkcg the inode is associated with.
      This patch implements inode_congested() and its wrappers which take
      @inode and determines the congestion state considering cgroup
      writeback.  The new functions replace bdi_*congested() calls in places
      where the query is about specific inode and task.
      There are several filesystem users which also fit this criteria but
      they should be updated when each filesystem implements cgroup
      writeback support.
      v2: Now that a given inode is associated with only one wb, congestion
          state can be determined independent from the asking task.  Drop
          @task.  Spotted by Vivek.  Also, converted to take @inode instead
          of @mapping and renamed to inode_congested().
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
  10. 20 Jan, 2015 1 commit
  11. 07 Aug, 2014 1 commit
  12. 07 Apr, 2014 1 commit
  13. 03 Apr, 2014 3 commits
    • Raghavendra K T's avatar
      mm/readahead.c: fix readahead failure for memoryless NUMA nodes and limit readahead pages · 6d2be915
      Raghavendra K T authored
      Currently max_sane_readahead() returns zero on the cpu whose NUMA node
      has no local memory which leads to readahead failure.  Fix this
      readahead failure by returning minimum of (requested pages, 512).  Users
      running applications on a memory-less cpu which needs readahead such as
      streaming application see considerable boost in the performance.
      fadvise experiment with FADV_WILLNEED on a PPC machine having memoryless
      CPU with 1GB testfile (12 iterations) yielded around 46.66% improvement.
      fadvise experiment with FADV_WILLNEED on a x240 machine with 1GB
      testfile 32GB* 4G RAM numa machine (12 iterations) showed no impact on
      the normal NUMA cases w/ patch.
        Kernel       Avg  Stddev
        base      7.4975   3.92%
        patched   7.4174   3.26%
      [Andrew: making return value PAGE_SIZE independent]
      Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: default avatarRaghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
      Acked-by: default avatarJan Kara <jack@suse.cz>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Cc: David Rientjes <rientjes@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Johannes Weiner's avatar
      mm + fs: prepare for non-page entries in page cache radix trees · 0cd6144a
      Johannes Weiner authored
      shmem mappings already contain exceptional entries where swap slot
      information is remembered.
      To be able to store eviction information for regular page cache, prepare
      every site dealing with the radix trees directly to handle entries other
      than pages.
      The common lookup functions will filter out non-page entries and return
      NULL for page cache holes, just as before.  But provide a raw version of
      the API which returns non-page entries as well, and switch shmem over to
      use it.
      Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: default avatarRik van Riel <riel@redhat.com>
      Reviewed-by: default avatarMinchan Kim <minchan@kernel.org>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Bob Liu <bob.liu@oracle.com>
      Cc: Christoph Hellwig <hch@infradead.org>
      Cc: Dave Chinner <david@fromorbit.com>
      Cc: Greg Thelen <gthelen@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Jan Kara <jack@suse.cz>
      Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
      Cc: Luigi Semenzato <semenzato@google.com>
      Cc: Mel Gorman <mgorman@suse.de>
      Cc: Metin Doslu <metin@citusdata.com>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Ozgun Erdogan <ozgun@citusdata.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Roman Gushchin <klamm@yandex-team.ru>
      Cc: Ryan Mallon <rmallon@gmail.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Johannes Weiner's avatar
      mm: filemap: move radix tree hole searching here · e7b563bb
      Johannes Weiner authored
      The radix tree hole searching code is only used for page cache, for
      example the readahead code trying to get a a picture of the area
      surrounding a fault.
      It sufficed to rely on the radix tree definition of holes, which is
      "empty tree slot".  But this is about to change, though, as shadow page
      descriptors will be stored in the page cache after the actual pages get
      evicted from memory.
      Move the functions over to mm/filemap.c and make them native page cache
      operations, where they can later be adapted to handle the new definition
      of "page cache hole".
      Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Reviewed-by: default avatarRik van Riel <riel@redhat.com>
      Reviewed-by: default avatarMinchan Kim <minchan@kernel.org>
      Acked-by: default avatarMel Gorman <mgorman@suse.de>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Bob Liu <bob.liu@oracle.com>
      Cc: Christoph Hellwig <hch@infradead.org>
      Cc: Dave Chinner <david@fromorbit.com>
      Cc: Greg Thelen <gthelen@google.com>
      Cc: Hugh Dickins <hughd@google.com>
      Cc: Jan Kara <jack@suse.cz>
      Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
      Cc: Luigi Semenzato <semenzato@google.com>
      Cc: Metin Doslu <metin@citusdata.com>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Ozgun Erdogan <ozgun@citusdata.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Roman Gushchin <klamm@yandex-team.ru>
      Cc: Ryan Mallon <rmallon@gmail.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Vlastimil Babka <vbabka@suse.cz>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  14. 30 Jan, 2014 1 commit
  15. 13 Nov, 2013 2 commits
  16. 11 Sep, 2013 1 commit
    • Fengguang Wu's avatar
      readahead: make context readahead more conservative · 2cad4018
      Fengguang Wu authored
      This helps performance on moderately dense random reads on SSD.
      Transaction-Per-Second numbers provided by Taobao:
      		QPS	case
      		7536	disable context readahead totally
      w/ patch:	7129	slower size rampup and start RA on the 3rd read
      		6717	slower size rampup
      w/o patch:	5581	unmodified context readahead
      Before, readahead will be started whenever reading page N+1 when it happen
      to read N recently.  After patch, we'll only start readahead when *three*
      random reads happen to access pages N, N+1, N+2.  The probability of this
      happening is extremely low for pure random reads, unless they are very
      dense, which actually deserves some readahead.
      Also start with a smaller readahead window.  The impact to interleaved
      sequential reads should be small, because for a long run stream, the the
      small readahead window rampup phase is negletable.
      The context readahead actually benefits clustered random reads on HDD
      whose seek cost is pretty high.  However as SSD is increasingly used for
      random read workloads it's better for the context readahead to concentrate
      on interleaved sequential reads.
      Another SSD rand read test from Miao
              # file size:        2GB
              # read IO amount: 625MB
              sysbench --test=fileio          \
                      --max-requests=10000    \
                      --num-threads=1         \
                      --file-num=1            \
                      --file-block-size=64K   \
                      --file-test-mode=rndrd  \
                      --file-fsync-freq=0     \
                      --file-fsync-end=off    run
      shows the performance of btrfs grows up from 69MB/s to 121MB/s, ext4 from
      104MB/s to 121MB/s.
      Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
      Tested-by: default avatarTao Ma <tm@tao.ma>
      Tested-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  17. 22 May, 2013 1 commit
    • Lukas Czerner's avatar
      mm: change invalidatepage prototype to accept length · d47992f8
      Lukas Czerner authored
      Currently there is no way to truncate partial page where the end
      truncate point is not at the end of the page. This is because it was not
      needed and the functionality was enough for file system truncate
      operation to work properly. However more file systems now support punch
      hole feature and it can benefit from mm supporting truncating page just
      up to the certain point.
      Specifically, with this functionality truncate_inode_pages_range() can
      be changed so it supports truncating partial page at the end of the
      range (currently it will BUG_ON() if 'end' is not at the end of the
      This commit changes the invalidatepage() address space operation
      prototype to accept range to be invalidated and update all the instances
      for it.
      We also change the block_invalidatepage() in the same way and actually
      make a use of the new length argument implementing range invalidation.
      Actual file system implementations will follow except the file systems
      where the changes are really simple and should not change the behaviour
      in any way .Implementation for truncate_page_range() which will be able
      to accept page unaligned ranges will follow as well.
      Signed-off-by: default avatarLukas Czerner <lczerner@redhat.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Hugh Dickins <hughd@google.com>
  18. 04 Mar, 2013 1 commit
  19. 27 Sep, 2012 2 commits
  20. 29 May, 2012 1 commit
  21. 31 Oct, 2011 1 commit
  22. 25 May, 2011 1 commit
  23. 10 Mar, 2011 2 commits
  24. 25 May, 2010 1 commit
  25. 07 Apr, 2010 1 commit
  26. 30 Mar, 2010 1 commit
    • Tejun Heo's avatar
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking... · 5a0e3ad6
      Tejun Heo authored
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
      percpu.h is included by sched.h and module.h and thus ends up being
      included when building most .c files.  percpu.h includes slab.h which
      in turn includes gfp.h making everything defined by the two files
      universally available and complicating inclusion dependencies.
      percpu.h -> slab.h dependency is about to be removed.  Prepare for
      this change by updating users of gfp and slab facilities include those
      headers directly instead of assuming availability.  As this conversion
      needs to touch large number of source files, the following script is
      used as the basis of conversion.
      The script does the followings.
      * Scan files for gfp and slab usages and update includes such that
        only the necessary includes are there.  ie. if only gfp is used,
        gfp.h, if slab is used, slab.h.
      * When the script inserts a new include, it looks at the include
        blocks and try to put the new include such that its order conforms
        to its surrounding.  It's put in the include block which contains
        core kernel includes, in the same order that the rest are ordered -
        alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
        doesn't seem to be any matching order.
      * If the script can't find a place to put a new include (mostly
        because the file doesn't have fitting include block), it prints out
        an error message indicating which .h file needs to be added to the
      The conversion was done in the following steps.
      1. The initial automatic conversion of all .c files updated slightly
         over 4000 files, deleting around 700 includes and adding ~480 gfp.h
         and ~3000 slab.h inclusions.  The script emitted errors for ~400
      2. Each error was manually checked.  Some didn't need the inclusion,
         some needed manual addition while adding it to implementation .h or
         embedding .c file was more appropriate for others.  This step added
         inclusions to around 150 files.
      3. The script was run again and the output was compared to the edits
         from #2 to make sure no file was left behind.
      4. Several build tests were done and a couple of problems were fixed.
         e.g. lib/decompress_*.c used malloc/free() wrappers around slab
         APIs requiring slab.h to be added manually.
      5. The script was run on all .h files but without automatically
         editing them as sprinkling gfp.h and slab.h inclusions around .h
         files could easily lead to inclusion dependency hell.  Most gfp.h
         inclusion directives were ignored as stuff from gfp.h was usually
         wildly available and often used in preprocessor macros.  Each
         slab.h inclusion directive was examined and added manually as
      6. percpu.h was updated not to include slab.h.
      7. Build test were done on the following configurations and failures
         were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
         distributed build env didn't work with gcov compiles) and a few
         more options had to be turned off depending on archs to make things
         build (like ipr on powerpc/64 which failed due to missing writeq).
         * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
         * powerpc and powerpc64 SMP allmodconfig
         * sparc and sparc64 SMP allmodconfig
         * ia64 SMP allmodconfig
         * s390 SMP allmodconfig
         * alpha SMP allmodconfig
         * um on x86_64 SMP allmodconfig
      8. percpu.h modifications were reverted so that it could be applied as
         a separate patch and serve as bisection point.
      Given the fact that I had only a couple of failures from tests on step
      6, I'm fairly confident about the coverage of this conversion patch.
      If there is a breakage, it's likely to be something in one of the arch
      headers which should be easily discoverable easily on most builds of
      the specific arch.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Guess-its-ok-by: default avatarChristoph Lameter <cl@linux-foundation.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
  27. 06 Mar, 2010 1 commit
    • Wu Fengguang's avatar
      readahead: introduce FMODE_RANDOM for POSIX_FADV_RANDOM · 0141450f
      Wu Fengguang authored
      This fixes inefficient page-by-page reads on POSIX_FADV_RANDOM.
      POSIX_FADV_RANDOM used to set ra_pages=0, which leads to poor performance:
      a 16K read will be carried out in 4 _sync_ 1-page reads.
      In other places, ra_pages==0 means
      - it's ramfs/tmpfs/hugetlbfs/sysfs/configfs
      - some IO error happened
      where multi-page read IO won't help or should be avoided.
      POSIX_FADV_RANDOM actually want a different semantics: to disable the
      *heuristic* readahead algorithm, and to use a dumb one which faithfully
      submit read IO for whatever application requests.
      So introduce a flag FMODE_RANDOM for POSIX_FADV_RANDOM.
      Note that the random hint is not likely to help random reads performance
      noticeably.  And it may be too permissive on huge request size (its IO
      size is not limited by read_ahead_kb).
      In Quentin's report (http://lkml.org/lkml/2009/12/24/145), the overall
      (NFS read) performance of the application increased by 313%!
      Tested-by: default avatarQuentin Barnes <qbarnes+nfs@yahoo-inc.com>
      Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
      Cc: Nick Piggin <npiggin@suse.de>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Steven Whitehouse <swhiteho@redhat.com>
      Cc: David Howells <dhowells@redhat.com>
      Cc: Jonathan Corbet <corbet@lwn.net>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Christoph Hellwig <hch@infradead.org>
      Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
      Cc: Chuck Lever <chuck.lever@oracle.com>
      Cc: <stable@kernel.org>			[2.6.33.x]
      Cc: <qbarnes+nfs@yahoo-inc.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  28. 17 Dec, 2009 1 commit
    • Hisashi Hifumi's avatar
      readahead: add blk_run_backing_dev · 65a80b4c
      Hisashi Hifumi authored
      I added blk_run_backing_dev on page_cache_async_readahead so readahead I/O
      is unpluged to improve throughput on especially RAID environment.
      The normal case is, if page N become uptodate at time T(N), then T(N) <=
      T(N+1) holds.  With RAID (and NFS to some degree), there is no strict
      ordering, the data arrival time depends on runtime status of individual
      disks, which breaks that formula.  So in do_generic_file_read(), just
      after submitting the async readahead IO request, the current page may well
      be uptodate, so the page won't be locked, and the block device won't be
      implicitly unplugged:
                     if (PageReadahead(page))
                      if (!PageUptodate(page))
                                      goto page_not_up_to_date;
      Therefore explicit unplugging can help.
      Following is the test result with dd.
      #dd if=testdir/testfile of=/dev/null bs=16384
      1048576+0 records in
      1048576+0 records out
      17179869184 bytes (17 GB) copied, 224.182 seconds, 76.6 MB/s
      1048576+0 records in
      1048576+0 records out
      17179869184 bytes (17 GB) copied, 206.465 seconds, 83.2 MB/s
      (7Disks RAID-0 Array)
      1054976+0 records in
      1054976+0 records out
      17284726784 bytes (17 GB) copied, 212.233 seconds, 81.4 MB/s
      1054976+0 records out
      17284726784 bytes (17 GB) copied, 198.878 seconds, 86.9 MB/s
      (7Disks RAID-5 Array)
      The patch was found to improve performance with the SCST scsi target
      driver.  See
      [akpm@linux-foundation.org: unbust comment layout]
      [akpm@linux-foundation.org: "fix" CONFIG_BLOCK=n]
      Signed-off-by: default avatarHisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
      Acked-by: default avatarWu Fengguang <fengguang.wu@intel.com>
      Cc: Jens Axboe <jens.axboe@oracle.com>
      Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
      Tested-by: default avatarRonald <intercommit@gmail.com>
      Cc: Bart Van Assche <bart.vanassche@gmail.com>
      Cc: Vladislav Bolkhovitin <vst@vlnb.net>
      Cc: Randy Dunlap <randy.dunlap@oracle.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  29. 17 Jun, 2009 6 commits
    • Wu Fengguang's avatar
      readahead: introduce context readahead algorithm · 10be0b37
      Wu Fengguang authored
      Introduce page cache context based readahead algorithm.
      This is to better support concurrent read streams in general.
      The current readahead algorithm detects interleaved reads in a _passive_ way.
      Given a sequence of interleaved streams 1,1001,2,1002,3,4,1003,5,1004,1005,6,...
      By checking for (offset == prev_offset + 1), it will discover the sequentialness
      between 3,4 and between 1004,1005, and start doing sequential readahead for the
      individual streams since page 4 and page 1005.
      The context readahead algorithm guarantees to discover the sequentialness no
      matter how the streams are interleaved. For the above example, it will start
      sequential readahead since page 2 and 1002.
      The trick is to poke for page @offset-1 in the page cache when it has no other
      clues on the sequentialness of request @offset: if the current requenst belongs
      to a sequential stream, that stream must have accessed page @offset-1 recently,
      and the page will still be cached now. So if page @offset-1 is there, we can
      take request @offset as a sequential access.
      - strictly interleaved reads  i.e. 1,1001,2,1002,3,1003,...
        the current readahead will take them as silly random reads;
        the context readahead will take them as two sequential streams.
      - cooperative IO processes   i.e. NFS and SCST
        They create a thread pool, farming off (sequential) IO requests to different
        threads which will be performing interleaved IO.
        It was not easy(or possible) to reliably tell from file->f_ra all those
        cooperative processes working on the same sequential stream, since they will
        have different file->f_ra instances. And NFSD's file->f_ra is particularly
        unusable, since their file objects are dynamically created for each request.
        The nfsd does have code trying to restore the f_ra bits, but not satisfactory.
        The new scheme is to detect the sequential pattern via looking up the page
        cache, which provides one single and consistent view of the pages recently
        accessed. That makes sequential detection for cooperative processes possible.
      Vladislav recommends the addition of context readahead as a result of his SCST
      benchmarks. It leads to 6%~40% performance gains in various cases and achieves
      equal performance in others.                http://lkml.org/lkml/2009/3/19/239
      In theory, it introduces one extra page cache lookup per random read.  However
      the below benchmark shows context readahead to be slightly faster, wondering..
      Randomly reading 200MB amount of data on a sparse file, repeat 20 times for
      each block size. The average throughputs are:
                             	original ra	context ra	gain
       4K random reads:	 65.561MB/s	 65.648MB/s	+0.1%
      16K random reads:	124.767MB/s	124.951MB/s	+0.1%
      64K random reads: 	162.123MB/s	162.278MB/s	+0.1%
      Cc: Jens Axboe <jens.axboe@oracle.com>
      Cc: Jeff Moyer <jmoyer@redhat.com>
      Tested-by: default avatarVladislav Bolkhovitin <vst@vlnb.net>
      Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Wu Fengguang's avatar
      readahead: move the random read case to bottom · 045a2529
      Wu Fengguang authored
      Split all readahead cases, and move the random one to bottom.
      No behavior changes.
      This is to prepare for the introduction of context readahead, and make it
      easy for inserting accounting/tracing points for each case.
      Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
      Cc: Vladislav Bolkhovitin <vst@vlnb.net>
      Cc: Jens Axboe <jens.axboe@oracle.com>
      Cc: Jeff Moyer <jmoyer@redhat.com>
      Cc: Nick Piggin <nickpiggin@yahoo.com.au>
      Cc: Ying Han <yinghan@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Wu Fengguang's avatar
      readahead: record mmap read-around states in file_ra_state · d30a1100
      Wu Fengguang authored
      Mmap read-around now shares the same code style and data structure with
      readahead code.
      This also removes do_page_cache_readahead().  Its last user, mmap
      read-around, has been changed to call ra_submit().
      The no-readahead-if-congested logic is dumped by the way.  Users will be
      pretty sensitive about the slow loading of executables.  So it's
      unfavorable to disabled mmap read-around on a congested queue.
      [akpm@linux-foundation.org: coding-style fixes]
      Cc: Nick Piggin <npiggin@suse.de>
      Signed-off-by: default avatarFengguang Wu <wfg@mail.ustc.edu.cn>
      Cc: Ying Han <yinghan@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Wu Fengguang's avatar
      readahead: remove sync/async readahead call dependency · 51daa88e
      Wu Fengguang authored
      The readahead call scheme is error-prone in that it expects the call sites
      to check for async readahead after doing a sync one.  I.e.
      			if (!page)
      			page = find_get_page();
      			if (page && PageReadahead(page))
      This is because PG_readahead could be set by a sync readahead for the
      _current_ newly faulted in page, and the readahead code simply expects one
      more callback on the same page to start the async readahead.  If the
      caller fails to do so, it will miss the PG_readahead bits and never able
      to start an async readahead.
      Eliminate this insane constraint by piggy-backing the async part into the
      current readahead window.
      Now if an async readahead should be started immediately after a sync one,
      the readahead logic itself will do it.  So the following code becomes
      valid: (the 'else' in particular)
      			if (!page)
      			else if (PageReadahead(page))
      Cc: Nick Piggin <npiggin@suse.de>
      Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
      Cc: Ying Han <yinghan@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Wu Fengguang's avatar
      readahead: increase interleaved readahead size · 160334a0
      Wu Fengguang authored
      Make sure interleaved readahead size is larger than request size.  This
      also makes the readahead window grow up more quickly.
      Reported-by: default avatarXu Chenfeng <xcf@ustc.edu.cn>
      Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
      Cc: Ying Han <yinghan@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    • Wu Fengguang's avatar
      readahead: remove one unnecessary radix tree lookup · caca7cb7
      Wu Fengguang authored
      (hit_readahead_marker != 0) means the page at @offset is present, so we
      can search for non-present page starting from @offset+1.
      Reported-by: default avatarXu Chenfeng <xcf@ustc.edu.cn>
      Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
      Cc: Ying Han <yinghan@google.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>