Re: [dm-devel] [PATCH v3 14/16] Gut bio_add_page()

[Dave Chinner <david fromorbit com>]

On Tue, May 29, 2012 at 08:02:08AM +0900, Tejun Heo wrote:
> (cc'ing Martin K. Petersen, hi!)
> 
> On Tue, May 29, 2012 at 06:38:39AM +0900, Tejun Heo wrote:
> > > With this patchset, you don't have to expose all the limits. You can 
> > > expose just a few most useful limits to avoid bio split in the cases 
> > > described above.
> > 
> > Yeah, if that actually helps, sure.  From what I read, dm is already
> > (ab)using merge_bvec_fn() like that anyway.
> 
> i thought a bit more about it and the only thing which makes sense to
> me is exposing the stripe granularity for striped devices -
> ie. something which says "if you go across this boundary, the
> performance characteristics including latency might get affected",
> which should fit nicely with the rest of topology information.
> Martin, adding that shouldn't be difficult, right?

We already have the optimal IO size/alignment field in the topology.
Doesn't this fit what you want exactly?

Cheers,

Dave.
-- 
Dave Chinner
david fromorbit com