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Re: [Xen-devel] [PATCH] tools/python/xend: VBD QoS policy bits

To: Christoph Egger <Christoph.Egger@xxxxxxx>
Subject: Re: [Xen-devel] [PATCH] tools/python/xend: VBD QoS policy bits
From: William Pitcock <nenolod@xxxxxxxxxxxxxxxx>
Date: Fri, 14 Aug 2009 20:21:15 +0400 (MSD)
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----- "Christoph Egger" <Christoph.Egger@xxxxxxx> wrote:

> Does this enforce the VBD to do 5000 IO operations or none at all or
> is
> this considered as an upper limit ?

That is dependent on the dom0 kernel, obviously... but my kernel-side
patch basically keeps the specified IOPS target as the upper limit, while
also allowing some level of initial burstability.

The goal here is to stop domUs which have gone swap-happy from degrading
system performance (especially with say, SANs) while the domU's owner is
not around to fix the problem... basically instead of the entire storage
volume's resources being consumed, the requests going to the physical volume
become ratelimited.

I submitted some patches earlier (around March, then May) which worked a
little bit differently, and feel that this way is more self-explanatory and
generally robust.


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