Re: [Lsf] [LSF/MM TOPIC] block-mq issues with FC

["Waskiewicz, PJ" <PJ.Waskiewicz@netapp.com>]

On Fri, 2016-04-08 at 13:40 -0400, Matthew Wilcox wrote:
> On Fri, Apr 08, 2016 at 01:29:26PM +0200, Hannes Reinecke wrote:
> >  - Interrupt steering needs to be controlled by block-mq instead of
>    the driver.  It's pointless to have each driver implement its own
>    policies on interrupt steering, irqbalanced remains a source of
>    end-user frustration, and block-mq can change the queue<->cpu
> mapping
>    without the driver's knowledge.

This is the same problem in the networking space as well.  When I added
affinity_hint to the irq_desc, and then that support into irqbalance,
my original approach was to allow the driver to assign affinities.
 This was shot down because a driver was influencing policy, versus
allowing userspace to do so.  Meh.

If there's something actionable out of this discussion that makes
interrupt steering better, I'd like to see us drive it into the
networking world as well.  That would also let me rip out the
affinity_hint stuff overall from irqbalance...

-PJ

-- 
PJ Waskiewicz
Principal Engineer, NetApp
e: pj.waskiewicz@netapp.com
d: 503.961.3705