[dm-devel] [PATCH 0/4] dm-latency: Introduction

[Mikulas Patocka]

On Fri, 27 Feb 2015, Bryn M. Reeves wrote:

> On Thu, Feb 26, 2015 at 02:45:43PM -0500, Laurence Oberman wrote:
> > For my particular use case its about providing the ability to warn on latencies being seen for multipath devices based on a given threshold.
> > Of course this can simply be a userspace tool using what we already expose and do the calculations to make it work.
> > When we have these latencies we then focus on which SAN path may or may not be contributing.
> > Within multipathd we can already configure service time as a load balancer, perhaps we can do the monitoring in the same place.
> > i.e. warn on service time above a threshold.
> 
> One limitation here is that the dm-mpath target is request-based.
> Currently dm-statistics are only available for bio-based targets. This
> means that to obtain fine-grained stats for multipath devices we need to
> insert a linear layer on top of the dm-mpath device.

Someone could hack dm statistics to work on request based targets.

Mikulas