All of lore.kernel.org
 help / color / mirror / Atom feed
From: Vivek Goyal <vgoyal@redhat.com>
To: Tao Ma <tm@tao.ma>
Cc: linux-kernel@vger.kernel.org, Tejun Heo <tj@kernel.org>,
	Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH V2] block/throttle: Add IO throttled information in blkio.throttle.
Date: Tue, 4 Sep 2012 09:35:29 -0400	[thread overview]
Message-ID: <20120904133528.GB13768@redhat.com> (raw)
In-Reply-To: <1346390109-3169-1-git-send-email-tm@tao.ma>

On Fri, Aug 31, 2012 at 01:15:09PM +0800, Tao Ma wrote:

[..]
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 1588c2d..9317d71 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -46,6 +46,8 @@ struct tg_stats_cpu {
>  	struct blkg_rwstat		service_bytes;
>  	/* total IOs serviced, post merge */
>  	struct blkg_rwstat		serviced;
> +	/* total IOs queued, not submitted to the underlying device. */
> +	struct blkg_rwstat		io_queued;
>  };

Couple of questions.

- blkg_rwstat is "unsigned" and io_queued can go negative too (Because
  throttled bio can very well be dispatched from other cpu from a worker
  thread). So is it a good idea to represent a negative number with 
  unsingned type?

- As this stat is per cpu, a reader might very well see negative (or a
  huge unsigned value) as number of io_queued. Not sure if that is acceptable.
  How would user space come to know whether it is a valid value or not. I
  thought per cpu stats are good for continuously increasing values but
  not necessarily for values which can increase as well as decrease.

Thanks
Vivek

  parent reply	other threads:[~2012-09-04 13:35 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
2012-09-04 13:35 ` Vivek Goyal [this message]
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:
  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=20120904133528.GB13768@redhat.com \
    --to=vgoyal@redhat.com \
    --cc=axboe@kernel.dk \
    --cc=linux-kernel@vger.kernel.org \
    --cc=tj@kernel.org \
    --cc=tm@tao.ma \
    /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.