1. 29 Apr, 2013 2 commits
  2. 22 Feb, 2013 1 commit
  3. 29 Nov, 2012 1 commit
    • Linus Torvalds's avatar
      direct-io: don't read inode->i_blkbits multiple times · ab73857e
      Linus Torvalds authored
      Since directio can work on a raw block device, and the block size of the
      device can change under it, we need to do the same thing that
      fs/buffer.c now does: read the block size a single time, using
      ACCESS_ONCE().
      
      Reading it multiple times can get different results, which will then
      confuse the code because it actually encodes the i_blksize in
      relationship to the underlying logical blocksize.
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ab73857e
  4. 09 Aug, 2012 1 commit
  5. 14 Jul, 2012 1 commit
  6. 31 May, 2012 1 commit
  7. 23 Feb, 2012 1 commit
    • Anton Altaparmakov's avatar
      Restore direct_io / truncate locking API · 37fbf4bf
      Anton Altaparmakov authored
      With kernel 3.1, Christoph removed i_alloc_sem and replaced it with
      calls (namely inode_dio_wait() and inode_dio_done()) which are
      EXPORT_SYMBOL_GPL() thus they cannot be used by non-GPL file systems and
      further inode_dio_wait() was pushed from notify_change() into the file
      system ->setattr() method but no non-GPL file system can make this call.
      
      That means non-GPL file systems cannot exist any more unless they do not
      use any VFS functionality related to reading/writing as far as I can
      tell or at least as long as they want to implement direct i/o.
      
      Both Linus and Al (and others) have said on LKML that this breakage of
      the VFS API should not have happened and that the change was simply
      missed as it was not documented in the change logs of the patches that
      did those changes.
      
      This patch changes the two function exports in question to be
      EXPORT_SYMBOL() thus restoring the VFS API as it used to be - accessible
      for all modules.
      
      Christoph, who introduced the two functions and exported them GPL-only
      is CC-ed on this patch to give him the opportunity to object to the
      symbols being changed in this manner if he did indeed intend them to be
      GPL-only and does not want them to become available to all modules.
      Signed-off-by: default avatarAnton Altaparmakov <anton@tuxera.com>
      CC: Christoph Hellwig <hch@infradead.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      37fbf4bf
  8. 12 Jan, 2012 2 commits
    • Andi Kleen's avatar
      dio: optimize cache misses in the submission path · 65dd2aa9
      Andi Kleen authored
      Some investigation of a transaction processing workload showed that a
      major consumer of cycles in __blockdev_direct_IO is the cache miss while
      accessing the block size.  This is because it has to walk the chain from
      block_dev to gendisk to queue.
      
      The block size is needed early on to check alignment and sizes.  It's only
      done if the check for the inode block size fails.  But the costly block
      device state is unconditionally fetched.
      
      - Reorganize the code to only fetch block dev state when actually
        needed.
      
      Then do a prefetch on the block dev early on in the direct IO path.  This
      is worth it, because there is substantial code run before we actually
      touch the block dev now.
      
      - I also added some unlikelies to make it clear the compiler that block
        device fetch code is not normally executed.
      
      This gave a small, but measurable improvement on a large database
      benchmark (about 0.3%)
      
      [akpm@linux-foundation.org: coding-style fixes]
      [sfr@canb.auug.org.au: using prefetch requires including prefetch.h]
      Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
      Cc: Jeff Moyer <jmoyer@redhat.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Christoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      65dd2aa9
    • Tao Ma's avatar
      fs/direct-io.c: calculate fs_count correctly in get_more_blocks() · ae55e1aa
      Tao Ma authored
      In get_more_blocks(), we use dio_count to calcuate fs_count and do some
      tricky things to increase fs_count if dio_count isn't aligned.  But
      actually it still has some corner cases that can't be coverd.  See the
      following example:
      
      	dio_write foo -s 1024 -w 4096
      
      (direct write 4096 bytes at offset 1024).  The same goes if the offset
      isn't aligned to fs_blocksize.
      
      In this case, the old calculation counts fs_count to be 1, but actually we
      will write into 2 different blocks (if fs_blocksize=4096).  The old code
      just works, since it will call get_block twice (and may have to allocate
      and create extents twice for filesystems like ext4).  So we'd better call
      get_block just once with the proper fs_count.
      Signed-off-by: default avatarTao Ma <boyu.mt@taobao.com>
      Cc: "Theodore Ts'o" <tytso@mit.edu>
      Cc: Christoph Hellwig <hch@lst.de>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ae55e1aa
  9. 28 Oct, 2011 7 commits
  10. 26 Jul, 2011 1 commit
  11. 20 Jul, 2011 4 commits
    • Christoph Hellwig's avatar
      fs: move inode_dio_done to the end_io handler · 72c5052d
      Christoph Hellwig authored
      For filesystems that delay their end_io processing we should keep our
      i_dio_count until the the processing is done.  Enable this by moving
      the inode_dio_done call to the end_io handler if one exist.  Note that
      the actual move to the workqueue for ext4 and XFS is not done in
      this patch yet, but left to the filesystem maintainers.  At least
      for XFS it's not needed yet either as XFS has an internal equivalent
      to i_dio_count.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      72c5052d
    • Christoph Hellwig's avatar
      fs: always maintain i_dio_count · df2d6f26
      Christoph Hellwig authored
      Maintain i_dio_count for all filesystems, not just those using DIO_LOCKING.
      This these filesystems to also protect truncate against direct I/O requests
      by using common code.  Right now the only non-DIO_LOCKING filesystem that
      appears to do so is XFS, which uses an opencoded variant of the i_dio_count
      scheme.
      
      Behaviour doesn't change for filesystems never calling inode_dio_wait.
      For ext4 behaviour changes when using the dioread_nonlock option, which
      previously was missing any protection between truncate and direct I/O reads.
      For ocfs2 that handcrafted i_dio_count manipulations are replaced with
      the common code now enable.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      df2d6f26
    • Christoph Hellwig's avatar
      fs: kill i_alloc_sem · bd5fe6c5
      Christoph Hellwig authored
      i_alloc_sem is a rather special rw_semaphore.  It's the last one that may
      be released by a non-owner, and it's write side is always mirrored by
      real exclusion.  It's intended use it to wait for all pending direct I/O
      requests to finish before starting a truncate.
      
      Replace it with a hand-grown construct:
      
       - exclusion for truncates is already guaranteed by i_mutex, so it can
         simply fall way
       - the reader side is replaced by an i_dio_count member in struct inode
         that counts the number of pending direct I/O requests.  Truncate can't
         proceed as long as it's non-zero
       - when i_dio_count reaches non-zero we wake up a pending truncate using
         wake_up_bit on a new bit in i_flags
       - new references to i_dio_count can't appear while we are waiting for
         it to read zero because the direct I/O count always needs i_mutex
         (or an equivalent like XFS's i_iolock) for starting a new operation.
      
      This scheme is much simpler, and saves the space of a spinlock_t and a
      struct list_head in struct inode (typically 160 bits on a non-debug 64-bit
      system).
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      bd5fe6c5
    • Christoph Hellwig's avatar
      fs: simplify handling of zero sized reads in __blockdev_direct_IO · f9b5570d
      Christoph Hellwig authored
      Reject zero sized reads as soon as we know our I/O length, and don't
      borther with locks or allocations that might have to be cleaned up
      otherwise.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      f9b5570d
  12. 10 Mar, 2011 2 commits
    • Jens Axboe's avatar
      block: kill off REQ_UNPLUG · 721a9602
      Jens Axboe authored
      With the plugging now being explicitly controlled by the
      submitter, callers need not pass down unplugging hints
      to the block layer. If they want to unplug, it's because they
      manually plugged on their own - in which case, they should just
      unplug at will.
      Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
      721a9602
    • Jens Axboe's avatar
      block: remove per-queue plugging · 7eaceacc
      Jens Axboe authored
      Code has been converted over to the new explicit on-stack plugging,
      and delay users have been converted to use the new API for that.
      So lets kill off the old plugging along with aops->sync_page().
      Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
      7eaceacc
  13. 20 Jan, 2011 1 commit
  14. 19 Jan, 2011 1 commit
  15. 26 Oct, 2010 1 commit
  16. 09 Sep, 2010 1 commit
    • Jeff Moyer's avatar
      O_DIRECT: fix the splitting up of contiguous I/O · 7a801ac6
      Jeff Moyer authored
      commit c2c6ca41 (direct-io: do not merge logically non-contiguous requests)
      introduced a bug whereby all O_DIRECT I/Os were submitted a page at a time
      to the block layer.  The problem is that the code expected
      dio->block_in_file to correspond to the current page in the dio.  In fact,
      it corresponds to the previous page submitted via submit_page_section.
      This was purely an oversight, as the dio->cur_page_fs_offset field was
      introduced for just this purpose.  This patch simply uses the correct
      variable when calculating whether there is a mismatch between contiguous
      logical blocks and contiguous physical blocks (as described in the
      comments).
      
      I also switched the if conditional following this check to an else if, to
      ensure that we never call dio_bio_submit twice for the same dio (in
      theory, this should not happen, anyway).
      
      I've tested this by running blktrace and verifying that a 64KB I/O was
      submitted as a single I/O.  I also ran the patched kernel through
      xfstests' aio tests using xfs, ext4 (with 1k and 4k block sizes) and btrfs
      and verified that there were no regressions as compared to an unpatched
      kernel.
      Signed-off-by: default avatarJeff Moyer <jmoyer@redhat.com>
      Acked-by: default avatarJosef Bacik <jbacik@redhat.com>
      Cc: Christoph Hellwig <hch@infradead.org>
      Cc: Chris Mason <chris.mason@oracle.com>
      Cc: <stable@kernel.org>		[2.6.35.x]
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      7a801ac6
  17. 09 Aug, 2010 1 commit
    • Christoph Hellwig's avatar
      sort out blockdev_direct_IO variants · eafdc7d1
      Christoph Hellwig authored
      Move the call to vmtruncate to get rid of accessive blocks to the callers
      in prepearation of the new truncate calling sequence.  This was only done
      for DIO_LOCKING filesystems, so the __blockdev_direct_IO_newtrunc variant
      was not needed anyway.  Get rid of blockdev_direct_IO_no_locking and
      its _newtrunc variant while at it as just opencoding the two additional
      paramters is shorted than the name suffix.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      eafdc7d1
  18. 27 Jul, 2010 1 commit
    • Christoph Hellwig's avatar
      direct-io: move aio_complete into ->end_io · 552ef802
      Christoph Hellwig authored
      Filesystems with unwritten extent support must not complete an AIO request
      until the transaction to convert the extent has been commited.  That means
      the aio_complete calls needs to be moved into the ->end_io callback so
      that the filesystem can control when to call it exactly.
      
      This makes a bit of a mess out of dio_complete and the ->end_io callback
      prototype even more complicated. 
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Reviewed-by: Jan Kara <jack@suse.cz> 
      Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
      552ef802
  19. 26 Jul, 2010 1 commit
  20. 27 May, 2010 1 commit
    • npiggin@suse.de's avatar
      fs: introduce new truncate sequence · 7bb46a67
      npiggin@suse.de authored
      Introduce a new truncate calling sequence into fs/mm subsystems. Rather than
      setattr > vmtruncate > truncate, have filesystems call their truncate sequence
      from ->setattr if filesystem specific operations are required. vmtruncate is
      deprecated, and truncate_pagecache and inode_newsize_ok helpers introduced
      previously should be used.
      
      simple_setattr is introduced for simple in-ram filesystems to implement
      the new truncate sequence. Eventually all filesystems should be converted
      to implement a setattr, and the default code in notify_change should go
      away.
      
      simple_setsize is also introduced to perform just the ATTR_SIZE portion
      of simple_setattr (ie. changing i_size and trimming pagecache).
      
      To implement the new truncate sequence:
      - filesystem specific manipulations (eg freeing blocks) must be done in
        the setattr method rather than ->truncate.
      - vmtruncate can not be used by core code to trim blocks past i_size in
        the event of write failure after allocation, so this must be performed
        in the fs code.
      - convert usage of helpers block_write_begin, nobh_write_begin,
        cont_write_begin, and *blockdev_direct_IO* to use _newtrunc postfixed
        variants. These avoid calling vmtruncate to trim blocks (see previous).
      - inode_setattr should not be used. generic_setattr is a new function
        to be used to copy simple attributes into the generic inode.
      - make use of the better opportunity to handle errors with the new sequence.
      
      Big problem with the previous calling sequence: the filesystem is not called
      until i_size has already changed.  This means it is not allowed to fail the
      call, and also it does not know what the previous i_size was. Also, generic
      code calling vmtruncate to truncate allocated blocks in case of error had
      no good way to return a meaningful error (or, for example, atomically handle
      block deallocation).
      
      Cc: Christoph Hellwig <hch@lst.de>
      Acked-by: default avatarJan Kara <jack@suse.cz>
      Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      7bb46a67
  21. 25 May, 2010 2 commits
    • Josef Bacik's avatar
      direct-io: do not merge logically non-contiguous requests · c2c6ca41
      Josef Bacik authored
      Btrfs cannot handle having logically non-contiguous requests submitted.  For
      example if you have
      
      Logical:  [0-4095][HOLE][8192-12287]
      Physical: [0-4095]      [4096-8191]
      
      Normally the DIO code would put these into the same BIO's.  The problem is we
      need to know exactly what offset is associated with what BIO so we can do our
      checksumming and unlocking properly, so putting them in the same BIO doesn't
      work.  So add another check where we submit the current BIO if the physical
      blocks are not contigous OR the logical blocks are not contiguous.
      Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      c2c6ca41
    • Josef Bacik's avatar
      direct-io: add a hook for the fs to provide its own submit_bio function · facd07b0
      Josef Bacik authored
      Because BTRFS can do RAID and such, we need our own submit hook so we can setup
      the bio's in the correct fashion, and handle checksum errors properly.  So there
      are a few changes here
      
      1) The submit_io hook.  This is straightforward, just call this instead of
      submit_bio.
      
      2) Allow the fs to return -ENOTBLK for reads.  Usually this has only worked for
      writes, since writes can fallback onto buffered IO.  But BTRFS needs the option
      of falling back on buffered IO if it encounters a compressed extent, since we
      need to read the entire extent in and decompress it.  So if we get -ENOTBLK back
      from get_block we'll return back and fallback on buffered just like the write
      case.
      
      I've tested these changes with fsx and everything seems to work.  Thanks,
      Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      facd07b0
  22. 17 Dec, 2009 1 commit
  23. 16 Dec, 2009 3 commits
    • Christoph Hellwig's avatar
      cleanup blockdev_direct_IO locking · 1e431f5c
      Christoph Hellwig authored
      Currently the locking in blockdev_direct_IO is a mess, we have three different
      locking types and very confusing checks for some of them.  The most
      complicated one is DIO_OWN_LOCKING for reads, which happens to not actually be
      used.
      
      This patch gets rid of the DIO_OWN_LOCKING - as mentioned above the read case
      is unused anyway, and the write side is almost identical to DIO_NO_LOCKING.
      The difference is that DIO_NO_LOCKING always sets the create argument for
      the get_blocks callback to zero, but we can easily move that to the actual
      get_blocks callbacks.  There are four users of the DIO_NO_LOCKING mode:
      gfs already ignores the create argument and thus is fine with the new
      version, ocfs2 only errors out if create were ever set, and we can remove
      this dead code now, the block device code only ever uses create for an
      error message if we are fully beyond the device which can never happen,
      and last but not least XFS will need the new behavour for writes.
      
      Now we can replace the lock_type variable with a flags one, where no flag
      means the DIO_NO_LOCKING behaviour and DIO_LOCKING is kept as the first
      flag.  Separate out the check for not allowing to fill holes into a separate
      flag, although for now both flags always get set at the same time.
      
      Also revamp the documentation of the locking scheme to actually make sense.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      1e431f5c
    • Christoph Hellwig's avatar
      direct-io: cleanup blockdev_direct_IO locking · 5fe878ae
      Christoph Hellwig authored
      Currently the locking in blockdev_direct_IO is a mess, we have three
      different locking types and very confusing checks for some of them.  The
      most complicated one is DIO_OWN_LOCKING for reads, which happens to not
      actually be used.
      
      This patch gets rid of the DIO_OWN_LOCKING - as mentioned above the read
      case is unused anyway, and the write side is almost identical to
      DIO_NO_LOCKING.  The difference is that DIO_NO_LOCKING always sets the
      create argument for the get_blocks callback to zero, but we can easily
      move that to the actual get_blocks callbacks.  There are four users of the
      DIO_NO_LOCKING mode: gfs already ignores the create argument and thus is
      fine with the new version, ocfs2 only errors out if create were ever set,
      and we can remove this dead code now, the block device code only ever uses
      create for an error message if we are fully beyond the device which can
      never happen, and last but not least XFS will need the new behavour for
      writes.
      
      Now we can replace the lock_type variable with a flags one, where no flag
      means the DIO_NO_LOCKING behaviour and DIO_LOCKING is kept as the first
      flag.  Separate out the check for not allowing to fill holes into a
      separate flag, although for now both flags always get set at the same
      time.
      
      Also revamp the documentation of the locking scheme to actually make
      sense.
      
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Cc: Dave Chinner <david@fromorbit.com>
      Cc: Badari Pulavarty <pbadari@us.ibm.com>
      Cc: Jeff Moyer <jmoyer@redhat.com>
      Cc: Jens Axboe <jens.axboe@oracle.com>
      Cc: Zach Brown <zach.brown@oracle.com>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Alex Elder <aelder@sgi.com>
      Cc: Mark Fasheh <mfasheh@suse.com>
      Cc: Joel Becker <joel.becker@oracle.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5fe878ae
    • Jeff Moyer's avatar
      dio: don't zero out the pages array inside struct dio · 23aee091
      Jeff Moyer authored
      Intel reported a performance regression caused by the following commit:
      
      commit 848c4dd5
      Author: Zach Brown <zach.brown@oracle.com>
      Date:   Mon Aug 20 17:12:01 2007 -0700
      
          dio: zero struct dio with kzalloc instead of manually
      
          This patch uses kzalloc to zero all of struct dio rather than
          manually trying to track which fields we rely on being zero.  It
          passed aio+dio stress testing and some bug regression testing on
          ext3.
      
          This patch was introduced by Linus in the conversation that lead up
          to Badari's minimal fix to manually zero .map_bh.b_state in commit:
      
            6a648fa7
      
          It makes the code a bit smaller.  Maybe a couple fewer cachelines to
          load, if we're lucky:
      
             text    data     bss     dec     hex filename
          3285925  568506 1304616 5159047  4eb887 vmlinux
          3285797  568506 1304616 5158919  4eb807 vmlinux.patched
      
          I was unable to measure a stable difference in the number of cpu
          cycles spent in blockdev_direct_IO() when pushing aio+dio 256K reads
          at ~340MB/s.
      
          So the resulting intent of the patch isn't a performance gain but to
          avoid exposing ourselves to the risk of finding another field like
          .map_bh.b_state where we rely on zeroing but don't enforce it in the
          code.
      
      Zach surmised that zeroing out the page array was what caused most of
      the problem, and suggested the approach taken in the attached patch for
      resolving the issue.  Intel re-tested with this patch and saw a 0.6%
      performance gain (the original regression was 0.5%).
      
      [akpm@linux-foundation.org: add comment]
      Signed-off-by: default avatarJeff Moyer <jmoyer@redhat.com>
      Acked-by: default avatarZach Brown <zach.brown@oracle.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      23aee091
  24. 26 Nov, 2009 1 commit
    • Vivek Goyal's avatar
      Fix regression in direct writes performance due to WRITE_ODIRECT flag removal · d9449ce3
      Vivek Goyal authored
      There seems to be a regression in direct write path due to following
      commit in for-2.6.33 branch of block tree.
      
      commit 1af60fbd
      Author: Jeff Moyer <jmoyer@redhat.com>
      Date:   Fri Oct 2 18:56:53 2009 -0400
      
          block: get rid of the WRITE_ODIRECT flag
      
      Marking direct writes as WRITE_SYNC_PLUG instead of WRITE_ODIRECT, sets
      the NOIDLE flag in bio and hence in request. This tells CFQ to not expect
      more request from the queue and not idle on it (despite the fact that
      queue's think time is less and it is not seeky).
      
      So direct writers lose big time when competing with sequential readers.
      
      Using fio, I have run one direct writer and two sequential readers and
      following are the results with 2.6.32-rc7 kernel and with for-2.6.33
      branch.
      
      Test
      ====
      1 direct writer and 2 sequential reader running simultaneously.
      
      [global]
      directory=/mnt/sdc/fio/
      runtime=10
      
      [seqwrite]
      rw=write
      size=4G
      direct=1
      
      [seqread]
      rw=read
      size=2G
      numjobs=2
      
      2.6.32-rc7
      ==========
      direct writes: aggrb=2,968KB/s
      readers	     : aggrb=101MB/s
      
      for-2.6.33 branch
      =================
      direct write: aggrb=19KB/s
      readers	      aggrb=137MB/s
      
      This patch brings back the WRITE_ODIRECT flag, with the difference that we
      don't set the BIO_RW_UNPLUG flag so that device is not unplugged after
      submission of request and an explicit unplug from submitter is required.
      
      That way we fix the jeff's issue of not enough merging taking place in aio
      path as well as make sure direct writes get their fair share.
      
      After the fix
      =============
      for-2.6.33 + fix
      ----------------
      direct writes: aggrb=2,728KB/s
      reads: aggrb=103MB/s
      
      Thanks
      Vivek
      Signed-off-by: default avatarVivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      d9449ce3
  25. 28 Oct, 2009 1 commit
    • Jeff Moyer's avatar
      aio: implement request batching · cfb1e33e
      Jeff Moyer authored
      Hi,
      
      Some workloads issue batches of small I/O, and the performance is poor
      due to the call to blk_run_address_space for every single iocb.  Nathan
      Roberts pointed this out, and suggested that by deferring this call
      until all I/Os in the iocb array are submitted to the block layer, we
      can realize some impressive performance gains (up to 30% for sequential
      4k reads in batches of 16).
      Signed-off-by: default avatarJeff Moyer <jmoyer@redhat.com>
      Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
      cfb1e33e