[dm-devel] least-pending multipath path selector WAS (9/14/14 !!!!): Re: Powerpath vs dm-multipath - two points of FUD?

[Martin Wilck]

Hi Xose,

On Mon, 2019-04-01 at 01:16 +0200, Xose Vazquez Perez wrote:
> On 9/14/14 10:39 AM, Hannes Reinecke wrote:
> 
> > We do this with the switch to request-based multipathing.
> > Using one of the other load balancers (eg least-pending) and set
> > rr_min_io to '1' will give you exactly that behaviour.
> 
> As the original authors team, at HP, was dissolved ( 
> https://bugzilla.redhat.com/show_bug.cgi?id=438760#c14 )
> Hannes, do you consider least-pending mp selector helpful for
> upstream?
> 

I can't speak for Hannes, but I believe that the functionality provided
by this patch is mostly provided by the "queue-length" path selector
today. "service-time" has been the default since 2013, and most users
seem to be fine with that.

It's true that SLES kernels still support it, but I don't think it's
used much, if at all.

Even if the "least pending" selector was still needed, the patch would
need updating for current upstream, to accomodate the changes from
9659f811446a "dm mpath: push path selector locking down to path
selectors", and possibly other changes in the general dm/path selector
framework.

Martin

-- 
Dr. Martin Wilck <mwilck at suse.com>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)