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Re: [Qemu-devel] virtual machine halting and loosing connections


From: Kyle Hubert
Subject: Re: [Qemu-devel] virtual machine halting and loosing connections
Date: Wed, 28 Mar 2007 10:28:00 -0700

On 3/28/07, WaxDragon <address@hidden> wrote:
On 3/27/07, Kyle Hubert <address@hidden> wrote:

> Also, I have noticed that when using the ondemand governor for the
> host OS (AMD PowerNow) that QEMU doesn't register for some reason. My
> host CPU stays running at 1GHz, when it is capable of 2.6GHz. I can
> run anything on the host OS, and I see the cpu freq jump up, so it
> works on the host OS. I believe this may have something to do with
> kqemu's acceleration.

I have seen the same behavior with cpufreq, but I run the
'conservative' governor on my AMD.  Haven't decided if it's a bug or a
feature yet. ;0)

I was running ondemand, and I came to the conclusion it's a bug. If
you see this paper:

http://linux.inet.hr/ols2006_the_ondemand_governor.html

You'll see that the ondemand governor policy is based on the idle/busy
statistics from scheduler ticks. I believe that kqemu runs off of
ioctl's from /dev/kqemu, and perhaps the system call doesn't
accurately change this?

How do the processes run in kqemu? Is it a kernel thread? Section 7.3
in that PDF talks of real time threads affecting the ondemand
scheduler.

NOTE: conservative is a fork of ondemand, so it applies here.

I'll try running without kqemu, and see if I still have the problem.

-Kyle




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