[dm-devel] [PATCH V2 0/4]multipath-tools: some fixup and enhancement for path-latency

[Guan Junxiong]

Hi Christophe,

Please consider this series of patches.

This series of patches help to make IO processing more common for
path-latency prioritizer, make the multipath.conf more user-friendly
and fixup the error of calculation on log scale standard deviation.  

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, PATCH 1/4 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. PATCH 3/4 drops it and use a syntax that
similar to other prioritizers, for example :
"base_num=5 io_num=10".

PATCH 2/4 can be an independent patch.

Third, Martin has pointed that standard deviation in the path-latency prioritizer
is wrong. We have solved this and here come the PATCH 4/4.  


Thanks
Guan Junxiong


Changes from V1:
* add PATCH 4/4 
* rebase on the 0.7.3 tag

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(-)

Guan Junxiong (4):
  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
  multipath-tools: calculate standard deviation on a logarithmic scale
    for prioritizer path_latency

 libmultipath/prioritizers/path_latency.c | 321 ++++++++++++++++++++-----------
 libmultipath/prioritizers/weightedpath.c |  10 +-
 libmultipath/util.c                      |   9 +
 libmultipath/util.h                      |   1 +
 multipath/multipath.conf.5               |   2 +-
 5 files changed, 217 insertions(+), 126 deletions(-)

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2.11.1