From: Keith Busch <keith.busch@intel.com>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Keith Busch <keith.busch@intel.com>,
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: Thu, 25 Sep 2014 09:57:41 -0600 (MDT) [thread overview]
Message-ID: <alpine.LRH.2.03.1409250923390.4696@AMR> (raw)
In-Reply-To: <20140925001341.GA25145@redhat.com>
On Wed, 24 Sep 2014, Mike Snitzer wrote:
> Mike Snitzer <snitzer@redhat.com> wrote:
>> 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).
>
> Actually, Junichi did respond with why:
> http://www.redhat.com/archives/dm-devel/2014-June/msg00033.html
>
> So this needs more review and thought.
Thank you for all the background information. This definitely gives me
a lot more to think about.
For my part, the goal was to change as little as possible to get basic
blk-mq support working safely without regressing, and performance is
not even on my radar yet. I purposefully did not try to understand the
existing design well enough to propose re-arching. If we can address the
'request' life cycle management duality issue, would this be acceptable
as a stopgap for blk-mq support?
next prev parent reply other threads:[~2014-09-25 15:57 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
2014-09-25 0:13 ` Mike Snitzer
2014-09-25 15:57 ` Keith Busch [this message]
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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