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Re: [dm-devel] [PATCH 4/7] dm mpath: remove process_queued_ios()

On Tue, Feb 11 2014 at  1:03pm -0500,
Hannes Reinecke <hare suse de> wrote:

> On 02/11/2014 04:55 PM, Mike Snitzer wrote:
> >On Tue, Feb 11 2014 at  4:46am -0500,
> >Hannes Reinecke <hare suse de> wrote:
> >
> >>On 02/10/2014 02:30 PM, Mike Snitzer wrote:
> >>>
> >>>Just to verify, this seems to be the only outstanding question for this
> >>>patchset?
> >>>
> >>>What value are you using for HZ?  If this portion of the change does
> >>>turn out to be meaningul: Rather than tieing to HZ should we just use an
> >>>explicitly non-zero value for __pg_init_all_paths()'s @min_delay?
> >>>
> >>The actual amount here is irrelevant, as long as it's non-zero.
> >>It's just there to force execution of the work item off the current
> >>thread.
> >
> >I'm aware we just need a non-zero value.  My concern, as originally
> >raised by Junichi in an earlier reply when you had it as HZ/50, is that
> >the value could be 0 if HZ is really small.  While unlikely I see no
> >point allowing the variable nature of HZ compromise passing a non-zero
> >value here.  Best to just be explicit by passing 1 or something.
> >
> >All said, the question of why this is actually needed remains.  I trust
> >you're working on answering that via reproducer (by not forcing the use
> >of workqueue context)?
> >
> Precisely.
> But as this is a bit hard to trigger it might take some time.
> (you'll only be hitting this issue if you have to retry
> scsi_dh_activate, so you'll need to trigger this somehow).


> I hope to get it done this week.
> Is there any deadline which I might miss with that?

No, that'll be great.  We have some time until the 3.15 merge window


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