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



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?

Cheers,

Hannes
--
Dr. Hannes Reinecke		      zSeries & Storage
hare suse de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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