[PATCH 0/7] mm: faster get user pages

[Keith Busch]

Pinning user pages out of nvdimm dax memory is significantly slower
compared to system ram. Analysis points to software overhead incurred
from a radix tree lookup. This patch series fixes that by removing the
relatively costly dev_pagemap lookup that was repeated for each page,
significantly increasing gup time.

The first 5 patches are just updating the benchmark to help test and
demonstrate the value of the last 2 patches.

The results were compared with following benchmark command for device
DAX memory:

  # gup_benchmark -m $((12*1024)) -n 512 -L -f /dev/dax0.0

  Before: 1037581 usec
  After:   375786 usec

Not bad; the after is the same time as using baseline anonymous system
RAM after this patch set, where before was nearly 3x longer.

Keith Busch (7):
  mm/gup_benchmark: Time put_page
  mm/gup_benchmark: Add additional pinning methods
  tools/gup_benchmark: Fix 'write' flag usage
  tools/gup_benchmark: Allow user specified file
  tools/gup_benchmark: Add parameter for hugetlb
  mm/gup: Combine parameters into struct
  mm/gup: Cache dev_pagemap while pinning pages

 include/linux/huge_mm.h                    |  12 +-
 include/linux/hugetlb.h                    |   2 +-
 include/linux/mm.h                         |  27 ++-
 mm/gup.c                                   | 279 ++++++++++++++---------------
 mm/gup_benchmark.c                         |  36 +++-
 mm/huge_memory.c                           |  67 ++++---
 mm/nommu.c                                 |   6 +-
 tools/testing/selftests/vm/gup_benchmark.c |  40 ++++-
 8 files changed, 262 insertions(+), 207 deletions(-)

-- 
2.14.4