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Re: [Xen-devel] Re: VM disk I/O limit patch

To: Shaun Reitan <mailinglists@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: VM disk I/O limit patch
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Mon, 27 Jun 2011 11:41:48 -0400
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On Thu, Jun 23, 2011 at 01:45:36PM -0700, Shaun Reitan wrote:
> Does this match only limit throughput or can it also limit the guest
> by disk IOPS?  christopher aker had a patch way back for UML that

Just throughpout.

> did disk based qos.  What i really liked about that patch was that
> it allowed for bursting by using a bucket.  If i remember correctly
> you specified that a guest's bucket could hold say 4000 tokens, and
> the bucket would be filled with 10 tokens a second.  Each IO took
> one token from the bucket.  When the bucket was empty IO was paused
> and processed as the bucket was filled.  This allowed a guest to
> burst for a short period of time until that bucket was empty and
> then it would slowely be filled back up.

Uhhh... are you sure you are talking about the same patch.
> Also what was nice is that the guest had a /proc/ entry that told
> the customer how many tokens they currently had in their bucket.

OK.. but how would this help the customers? They don't have access
to the /proc in Dom0.
> I would like to see somthing like this in Xen, I've even thought
> about posting to the devel forums seeing if somebody wanted to write
> one for $$$

Why not use dm-ioband (here is a doc about it:
http://lwn.net/Articles/344441/) which has much more options and also
provide the bucket and tokens you are looking for.

[edit: Looks like dm-ioband never made it in the Linux kernel. But there
was something that I thought Vivek wrote that was superior to dm-ioband..
Ah, yes: blkio-controller.txt.

Look in Documentation/cgroups/blkio-controller.txt]

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