Re: queue_depth tracking from LLD

[Christof Schmitt <christof.schmitt@de.ibm.com>]

On Thu, Apr 16, 2009 at 10:38:06AM -0400, James Smart wrote:
> Mike Christie wrote:
[...]
> No good reason.  It should be in the midlayer, and that was the
> recommendation I made at storage summit a couple of years ago. It
> hasn't as, for the drivers that  care, they had already implemented
> it. It also isn't a relished task, as there will be lots of
> discussion on how the ramp-up should be implemented - which may
> mean, the need for more  algorithms.

zfcp is one of the drivers that don't have ramp-up/down mechanism in
place. And i am trying to understand what is required here.  Is there
currently work being done to get queue_depth ramp-up/down in the
midlayer?

>> If we moved code like that to the scsi layer, then is all the is needed 
>> is a interface to config this?

> Yep. As mentioned, figuring out what algorithm, for what device and
> configuration, will be the more interesting thing.

If the LLDs that currently have a private ramp-up/down mechanism in
place use a similar strategy, would it make sense to first move them
to common code that can be activated from a LLD? And later refine it
with device-specific behaviour?

--
Christof Schmitt