[dm-devel] [PATCH 0/3] multipath-tools: use direct IO and user-friend arguments for path-latency

[Guan Junxiong]

This series of patches help to make IO processing more common for
path-latency prioritizer and make it more user-friendly. 

First, the SCSI-to-NVMe translations which was blamed broken has been removed
since linux kernel 4.13, so that SG_IO IOCTL used in the reading is not
supported. Instead, this patch drops sg_read method and uses direct IO
reading both for NVMe device and SCSI device.

Second, the original prio_args for prioritizer is like this: 20|10 which
is somewhat unconvenient for user. Third patch drops it and use a syntax that
similar to other prioritizers, for example :
"base_num=5 io_num=10".

PATCH 2/3 can be an independent patch.

Those above are the two things being addressed by this series of patches.

Note:
Martin has pointed that standard deviation in the path-latency prioritizer
is wrong. We are solving this but it will take more days to prove the
correctness and verify this by testing.  

Thanks
Guan Junxiong


Junxiong Guan (3):
  multipath-tools: use direct IO for path latency prioritizer
  multipath-tools: move get_next_string to util
  multipath-tools: use user-friendly prio_args for path-latency

 libmultipath/prioritizers/path_latency.c | 156 +++++++++++++++++++++++--------
 libmultipath/prioritizers/weightedpath.c |  10 +-
 libmultipath/util.c                      |   9 ++
 libmultipath/util.h                      |   1 +
 multipath/multipath.conf.5               |   2 +-
 5 files changed, 127 insertions(+), 51 deletions(-)

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2.11.1