From: Mike Snitzer <snitzer@redhat.com>
To: Keith Busch <keith.busch@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>,
dm-devel@redhat.com, shivakrishna.merla@netapp.com,
Bart Van Assche <bvanassche@acm.org>,
jmoyer@redhat.com
Subject: Re: awful request merge results while simulating high IOPS multipath
Date: Wed, 25 Feb 2015 19:11:15 -0500 [thread overview]
Message-ID: <20150226001114.GA22484@redhat.com> (raw)
In-Reply-To: <alpine.LNX.2.00.1502252327150.32385@localhost.lm.intel.com>
On Wed, Feb 25 2015 at 6:57pm -0500,
Keith Busch <keith.busch@intel.com> wrote:
> On Wed, 25 Feb 2015, Mike Snitzer wrote:
> >On Wed, Feb 25 2015 at 1:17pm -0500,
> >Busch, Keith <keith.busch@intel.com> wrote:
> >>Our first bottleneck appears to be the device mapper's single lock
> >>request queue.
> >
> >Obviously if we switched dm-multipath over to blk-mq we'd eliminate
> >that. I'll see how things go and will share any changes I come up
> >with.
>
> Yes, I'm also looking at blk-mq. It appears conversion helps a lot.
Oh, so you've already started a conversion of request-based DM?
> I'm not sure though how many tags or h/w contexts to allocate to ensure
> there's enough but not too many. You can't use the underlying device's
> blk-tagset count (assuming you could even get to it) since those are
> potentially shared among many block devices.
I'm very new to the blk-mq model so I have some learning to do before
I'll be much help.
But there really won't be a one size fits all amount for those resources
will there? A multipath device can have _a lot_ of underlying paths.
next prev parent reply other threads:[~2015-02-26 0:11 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-24 16:44 [PATCH 0/4] dm: simplify request-based DM a bit and an RFC-like perf tweak Mike Snitzer
2015-02-24 16:44 ` [PATCH 1/4] dm: remove unnecessary wrapper around blk_lld_busy Mike Snitzer
2015-02-24 16:44 ` [PATCH 2/4] dm: remove request-based DM queue's lld_busy_fn hook Mike Snitzer
2015-02-24 16:44 ` [PATCH 3/4] dm: remove request-based logic from make_request_fn wrapper Mike Snitzer
2015-02-24 16:44 ` [RFC PATCH 4/4] dm: delay running the queue slightly during request completion Mike Snitzer
2015-02-24 16:51 ` Jens Axboe
2015-02-24 17:22 ` [RFC PATCH 4/4 v2] " Mike Snitzer
2015-02-24 17:52 ` Jens Axboe
2015-02-24 18:12 ` Mike Snitzer
2015-02-24 18:16 ` Jens Axboe
2015-02-24 18:32 ` Mike Snitzer
2015-02-25 0:56 ` awful request merge results while simulating high IOPS multipath Mike Snitzer
2015-02-25 4:14 ` Keith Busch
2015-02-25 15:11 ` Jens Axboe
2015-02-25 18:17 ` Busch, Keith
2015-02-25 22:10 ` Mike Snitzer
2015-02-25 23:57 ` Keith Busch
2015-02-26 0:11 ` Mike Snitzer [this message]
2015-02-26 0:28 ` Keith Busch
2015-02-25 4:38 ` FIXED! [was: awful request merge results while simulating high IOPS] multipath Mike Snitzer
2015-02-25 4:41 ` Mike Snitzer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20150226001114.GA22484@redhat.com \
--to=snitzer@redhat.com \
--cc=axboe@kernel.dk \
--cc=bvanassche@acm.org \
--cc=dm-devel@redhat.com \
--cc=jmoyer@redhat.com \
--cc=keith.busch@intel.com \
--cc=shivakrishna.merla@netapp.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.