[PATCH v5 0/2] ext4: Improve parallel I/O performance on NVDIMM

[Waiman Long <Waiman.Long@hpe.com>]

v4->v5:
 - Change patch 1 to disable i_dio_count update in do_dax_io().

v3->v4:
 - For patch 1, add the DIO_SKIP_DIO_COUNT flag to dax_do_io() calls
   only to address issue raised by Dave Chinner.

v2->v3:
 - Remove the percpu_stats helper functions and use percpu_counters
   instead.

v1->v2:
 - Remove percpu_stats_reset() which is not really needed in this
   patchset.
 - Move some percpu_stats* functions to the newly created
   lib/percpu_stats.c.
 - Add a new patch to support 64-bit statistics counts in 32-bit
   architectures.
 - Rearrange the patches by moving the percpu_stats patches to the
   front followed by the ext4 patches.

This patchset aims to improve parallel I/O performance of the ext4
filesystem on DAX.

Patch 1 disables update of the i_dio_count as all DAX I/Os are synchronous
and should be protected from whatever locking was done by the filesystem
caller or within dax_do_io() for read (DIO_LOCKING).

Patch 2 converts some ext4 statistics counts into percpu counts using
the helper functions.

Waiman Long (2):
  dax: Don't touch i_dio_count in dax_do_io()
  ext4: Make cache hits/misses per-cpu counts

 fs/dax.c                 |   14 ++++++--------
 fs/ext4/extents_status.c |   38 +++++++++++++++++++++++++++++---------
 fs/ext4/extents_status.h |    4 ++--
 3 files changed, 37 insertions(+), 19 deletions(-)