[dm-devel] [PATCH 0/4] Integrate dm-latency functionality to dm-statistics

[Mikulas Patocka]

Hi

Here I'm sending patches that add funcionality provided by dm-latency into 
dm-statistics framework. Dm-latency was introduced in this post 
https://www.redhat.com/archives/dm-devel/2015-February/msg00158.html , 
however, there is already similar framework dm-statistics in the kernel. 
In order to have cleaner and easier to maintain code, it is better to 
integrate dm-latency functionality into dm-statistics, rather than having 
two frameworks that do similar things.

This patch series makes these changes:
* it is possible to use precise time measurement with nanosecond 
  granularity (previously, time was measured in jiffies)
* it is possible to collect histogram of latencies. The histogram 
  boundaries may be selected by the user and there is unlimited number of 
  possible boundaries (in dm-latency, the histogram boundaries were fixed)
* it is possible to use dm-statistics on multipath

The documentation of these extensions is in 
Documentation/device-mapper/statistics.txt

I'd like to ask people who designed dm-latency to check this patchset, try 
to use it and tell us if it provides sufficient functionality to them (the 
indended functinality of dm-latency was to predict hard disk failures from 
i/o request latency histogram).

Mikulas