Date: Wed, 11 Jun 2008 15:42:28 -0700
From: Randy Dunlap <randy.dunlap@oracle.com>
To: Andrea Righi <righi.andrea@gmail.com>
Cc: balbir@linux.vnet.ibm.com, menage@google.com, matt@bluehost.com,
       roberto@unbit.it, akpm@linux-foundation.org,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] i/o bandwidth controller documentation
Message-Id: <20080611154228.ef269ff2.randy.dunlap@oracle.com>
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References: <1212791250-32320-2-git-send-email-righi.andrea@gmail.com>
Organization: Oracle Linux Eng.
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On Sat,  7 Jun 2008 00:27:28 +0200 Andrea Righi wrote:

> Documentation of the block device I/O bandwidth controller: description, usage,
> advantages and design.
> 
> Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
> ---
>  Documentation/controllers/io-throttle.txt |  150 +++++++++++++++++++++++++++++
>  1 files changed, 150 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/controllers/io-throttle.txt
> 
> diff --git a/Documentation/controllers/io-throttle.txt b/Documentation/controllers/io-throttle.txt
> new file mode 100644
> index 0000000..5373fa8
> --- /dev/null
> +++ b/Documentation/controllers/io-throttle.txt
> @@ -0,0 +1,150 @@
> +
> +               Block device I/O bandwidth controller
> +
> +1. Description
> +
> +This controller allows to limit the I/O bandwidth of specific block devices for
> +specific process containers (cgroups) imposing additional delays on I/O
> +requests for those processes that exceed the limits defined in the control
> +group filesystem.
> +
> +Bandwidth limiting rules offer better control over QoS with respect to priority
> +or weight-based solutions that only give information about applications'
> +relative performance requirements.
> +
> +The goal of the I/O bandwidth controller is to improve performance
> +predictability and QoS of the different control groups sharing the same block
> +devices.
> +
> +NOTE: if you're looking for a way to improve the overall throughput of the
> +system probably you should use a different solution.
> +
> +2. User Interface
> +
> +A new I/O bandwidth limitation rule is described using the file
> +blockio.bandwidth.
> +
> +The same file can be used to set multiple rules for different block devices
> +relatively to the same cgroup.

   relative

> +
> +The syntax is the following:
> +# /bin/echo DEVICE:BANDWIDTH > CGROUP/blockio.bandwidth
> +
> +- DEVICE is the name of the device the limiting rule is applied to,
> +- BANDWIDTH is the maximum I/O bandwidth on DEVICE allowed by CGROUP,
> +- CGROUP is the name of the limited process container.


Thanks.
---
~Randy
"'Daemon' is an old piece of jargon from the UNIX operating system,
where it referred to a piece of low-level utility software, a
fundamental part of the operating system."
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