archive mirror
 help / color / mirror / Atom feed
From: Tejun Heo <>
To: Tao Ma <>
Cc:, Vivek Goyal <>,
	Jens Axboe <>
Subject: Re: [PATCH V2] block/throttle: Add IO throttled information in blkio.throttle.
Date: Tue, 4 Sep 2012 12:13:11 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hello, Tao Ma.

On Sat, Sep 01, 2012 at 09:58:43PM +0800, Tao Ma wrote:
> Vivek and I have talked about its usage in my first try. See the thread
> here.
> And I am OK to say it again here. In our case, we use flashcache as a
> block device and the bad thing is that flashcache is a bio-based dm
> target and we can't use block io controller here to control the weight
> of different cgroups. So io throttle is chosen. But as io throttle can
> only set a hard upper limit for different instances, it makes the
> control not flexible enough. Say with io controller, if there is no
> requests form the cgroup with weight 1000, a cgroup with 500 can use the
> whole bandwidth of the underlying device. But if we set 1000 iops for
> cgroup A and 500 iops for cgroup B in io throttle, cgroup B can't exceed
> its limit even if cgroup A has no request pending. So if we can export
> the io_queued information out to the system admin, they can write some
> daemon and in the above case, increase the upper limit of cgroup B to
> some number say 1000. It helps us to utilize the device more
> efficiently. Does it make sense to you?

Somewhat, in a pretty twisted way. :P

> > Adding throttle.io_queued could be a bit more consistent?
> sorry, I don't know what is your meaning here. You mean some codes like
> 	blkg_rwstat_add(&stats_cpu->throttle.io_queude, rw, 1)?

So, there already is io_dispatched, so if you have io_queued, you can
read the two and calculate the difference from userland (reading
io_queued first would probably be better to avoid triggering the
throttled condition spuriously).  That way, you don't have to worry
about synchronizing stats across cpus and it's a simple addition of a
stat conter.



  reply	other threads:[~2012-09-04 19:13 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-31  5:15 [PATCH V2] block/throttle: Add IO throttled information in blkio.throttle Tao Ma
2012-09-01  1:05 ` Tejun Heo
2012-09-01 13:58   ` Tao Ma
2012-09-04 19:13     ` Tejun Heo [this message]
2012-09-04 13:35 ` Vivek Goyal
2012-09-04 14:12   ` Tao Ma
2012-09-04 14:23     ` Vivek Goyal
2012-09-04 14:45     ` Vivek Goyal

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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \

* 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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).