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Re: [Xen-devel] credit scheduler issues in 64bit hypervisor

To: Rik van Riel <riel@xxxxxxxxxx>
Subject: Re: [Xen-devel] credit scheduler issues in 64bit hypervisor
From: Steven Hand <Steven.Hand@xxxxxxxxxxxx>
Date: Sat, 01 Jul 2006 14:46:39 +0100
Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Steven.Hand@xxxxxxxxxxxx, "Zheng, Jeff" <jeff.zheng@xxxxxxxxx>
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>On Wed, 28 Jun 2006, Ian Pratt wrote:
>> > When we use credit scheduler in 64bit hypervisor, we see these issues:
>> > + Booting 32bit VMX domain hangs at "ACPI: Unable to locate RSDP".
>> > + Booting 32pae VMX domain will get a kernel panic.
>> > + Booting indows SP1/SP2 Guest will crash guest OS.
>> > 
>> > We don't see these issues with BVT scheduler.
>> Is this specific to 64b hypervisor? We do most HVM testing on 32b PAE
>> and haven't seen these issues.
>I am also seeing an instant reboot if I try the credit
>scheduler on my x86-64 system.  The reboot happens every
>time I try to start a VT guest domain - haven't tried
>paravirt, since I need one of the VT domains :)

Have you got any debug output from Xen ? (and are you running a debug 

>Please don't make the credit scheduler the default until
>it actually works.

I'm not sure this is a credit scheduler bug - it seems rather more likely
to be a vmx bug shaken out by the more aggressive load balancing of the 
new scheduler. Masking such bugs by using another scheduler doesn't seem
like a great idea to me.

Of course, difficult to be certain of the exact cause without some debug
output or similar. 



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