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From: Mike Snitzer <snitzer@redhat.com>
To: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	Jun'ichi Nomura <j-nomura@ce.jp.nec.com>,
	dm-devel@redhat.com
Subject: Re: dm-mpath: Work with blk multi-queue drivers
Date: Wed, 24 Sep 2014 14:48:35 -0400	[thread overview]
Message-ID: <20140924184834.GB23052@redhat.com> (raw)
In-Reply-To: <20140924183453.GA23052@redhat.com>

On Wed, Sep 24 2014 at  2:34pm -0400,
Mike Snitzer <snitzer@redhat.com> wrote:

> 
> I never did take the time to properly review Hannes' proposal but now
> that you're floating this blk-mq support for DM core (and DM mpath) I'm
> clearly going to have to take this all on in a much more focused way.
> 
> Christoph/Hannes/Junichi/Keith/others, can you see a way forward that
> offers a lighter request-based DM that makes required callouts to (new?)
> block interfaces that helps us abstract the old request and blk-mq
> request allocation, etc?

(sorry about replying to myself...)

SO revisiting that thread from above, these posts stand out:
http://www.redhat.com/archives/dm-devel/2014-June/msg00026.html
http://www.redhat.com/archives/dm-devel/2014-June/msg00028.html

I'd love to see us get rid of request-based DM's bio cloning for each
cloned request (we never did get an answer from the NEC guys to know
_why_ that was done).

http://www.redhat.com/archives/dm-devel/2014-June/msg00029.html

But I now see what Christoph was saying about needing the call
blk_get_request() against the low level path... and that completely
avoiding request cloning like Hannes did is a non-starter for blk-mq.

So if we could:
1) rip out the rq-based DM's cloning of all bios in a request
2) rebase Keith's approach ontop of 1) then we could go from there
   - but happy to put more thought in upfront to avoid busy work; and
     I'd encourage everyone else to do the same...

  reply	other threads:[~2014-09-24 18:48 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-23 17:03 [PATCH] dm-mpath: Work with blk multi-queue drivers Keith Busch
2014-09-24  9:02 ` Hannes Reinecke
2014-09-24 14:27   ` Christoph Hellwig
2014-09-24 14:52 ` Christoph Hellwig
2014-09-24 17:20   ` Keith Busch
2014-09-24 18:34     ` Mike Snitzer
2014-09-24 18:48       ` Mike Snitzer [this message]
2014-09-25  0:13         ` Mike Snitzer
2014-09-25 15:57           ` Keith Busch
2014-09-25 16:08             ` Christoph Hellwig
2014-09-25 16:12             ` Mike Snitzer
2014-09-29 23:58               ` Junichi Nomura
2014-09-30 14:18                 ` Mike Snitzer
2014-09-30 23:43                   ` Junichi Nomura

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