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Re: [Xen-devel] Question about the ability of credit scheduler to handle

To: Yuehai Xu <yuehaixu@xxxxxxxxx>
Subject: Re: [Xen-devel] Question about the ability of credit scheduler to handle I/O and CPU intensive VMs
From: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Date: Mon, 18 Oct 2010 11:25:42 +0100
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I think this is probably an area open for research. :-)

I would think 500us or 1ms would be decent options, but that's mostly a guess.


On 12/10/10 13:42, Yuehai Xu wrote:
Sorry for making noise, the mode is PV. Because my scheduler is set to
CPU fairness only, so the number I calculated is almost the same, as
long as I set it to I/O favor, the number is different.

Here is another question, since we always say a short period of time,
how long it should be? 500us? 50us? 1ms? is there any hint that I can


Remind me, are you running in HVM mode, or PV mode?

That sounds unusual.  Is it the number of events delivered, or the
number of times the guest woke up?  NB they're not the same -- an HVM
guest will block and then wake up on the completion of an I/O
instruction which is handled by qemu.

If you're running in HVM mode, you can use "xenalyze -s" will give you
a summary of the trace.  In the summary you can see not only now many
times a VM woke up, but which interrupt was delivered how many times.

At the moment, from Xen's perspective, an event delivery is an event
delivery.  You'd have to manually add some way of classifying an event
as "I/O".


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