From mboxrd@z Thu Jan  1 00:00:00 1970
From: George Dunlap <george.dunlap@eu.citrix.com>
Subject: Re: [xen-unstable test] 17139: regressions - FAIL
Date: Thu, 7 Mar 2013 16:47:54 +0000
Message-ID: <5138C4BA.7020506@eu.citrix.com>
References: <osstest-17139-mainreport@xen.org>
	<51389ABE02000078000C3ECD@nat28.tlf.novell.com>
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To: Jan Beulich <JBeulich@suse.com>
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On 07/03/13 12:48, Jan Beulich wrote:
>>>> On 07.03.13 at 13:38, xen.org <ian.jackson@eu.citrix.com> wrote:
>> flight 17139 xen-unstable real [real]
>> http://www.chiark.greenend.org.uk/~xensrcts/logs/17139/
>>
>> Regressions :-(
>>
>> Tests which did not succeed and are blocking,
>> including tests which could not be run:
>>   test-amd64-i386-xl-credit2    5 xen-boot                  fail REGR. vs. 16772
> George,
>
> pretty likely something you want to take a look at:
>
> Mar  7 02:39:54.552252 (XEN) ****************************************
> Mar  7 02:39:54.560215 (XEN) Panic on CPU 0:
> Mar  7 02:39:54.560256 (XEN) Assertion 'rt_credit >= 0' failed at sched_credit2.c:1559
> Mar  7 02:39:54.560314 (XEN) ****************************************

Very interesting...  it seems that under certain circumstances, even if 
the scheduler sets a timer to pre-empt a VM for 200us, that the VM may 
run for >11ms.  Since the "reset" assumes that your negative credit will 
never be less than -200us, it merely adds 10ms.  So even after the 
reset, the VM is still in negative credits.

Let me see what I want to do about that...

  -George