crash due to frequent access to csched_dom

crash due to frequent access to csched_dom

[David Xu]

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Hi,

I am changing the credit1 scheduler. But I encountered a problem that the
system will crash if I use some fileds  of struct csched_dom (e.t.
sdom->weight, sdom->credit ) frequently in the csched_vcpu_acct() or
csched_runq_sort(). It seems strange. Can anyone give me some suggestion or
share your experience? Thanks.

Regards,
Cong

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Re: crash due to frequent access to csched_dom

[George Dunlap]

On Wed, Jul 13, 2011 at 5:54 PM, David Xu <davidxu06@gmail.com> wrote:
> Hi,
>
> I am changing the credit1 scheduler. But I encountered a problem that the
> system will crash if I use some fileds  of struct csched_dom (e.t.
> sdom->weight, sdom->credit ) frequently in the csched_vcpu_acct() or
> csched_runq_sort(). It seems strange. Can anyone give me some suggestion or
> share your experience? Thanks.

Did you get any output on the serial console?

If you don't have a serial console set up, that's the first thing to
do.  It's immensely helpful when doing Xen debugging, especially
scheduler stuff.

You can learn more about setting up a Xen serial console here:

http://wiki.xensource.com/xenwiki/XenSerialConsole

 -George

Re: crash due to frequent access to csched_dom

[David Xu]

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Sorry, I do not have the serial port device now. It seems I can not access
to csched_dom struct frequently during scheduling tick. For example, in each
schedule tick, I will adjust the runqueue sequence according to the latency
(another parameter added by myself) and remained credits of each domainU.
This part code is added to the csched_vcpu_acct() or csched_runq_sort(). I
also try accessing to sdom->weight, it also does not work. OK, I will try to
set up a serial console firstly. Thanks very much.

Regards,
Cong

2011/7/14 George Dunlap <George.Dunlap@eu.citrix.com>

> On Wed, Jul 13, 2011 at 5:54 PM, David Xu <davidxu06@gmail.com> wrote:
> > Hi,
> >
> > I am changing the credit1 scheduler. But I encountered a problem that the
> > system will crash if I use some fileds  of struct csched_dom (e.t.
> > sdom->weight, sdom->credit ) frequently in the csched_vcpu_acct() or
> > csched_runq_sort(). It seems strange. Can anyone give me some suggestion
> or
> > share your experience? Thanks.
>
> Did you get any output on the serial console?
>
> If you don't have a serial console set up, that's the first thing to
> do.  It's immensely helpful when doing Xen debugging, especially
> scheduler stuff.
>
> You can learn more about setting up a Xen serial console here:
>
> http://wiki.xensource.com/xenwiki/XenSerialConsole
>
>  -George
>

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Re: crash due to frequent access to csched_dom

[George Dunlap]

On Thu, Jul 14, 2011 at 7:42 PM, David Xu <davidxu06@gmail.com> wrote:
> Sorry, I do not have the serial port device now. It seems I can not access
> to csched_dom struct frequently during scheduling tick. For example, in each
> schedule tick, I will adjust the runqueue sequence according to the latency
> (another parameter added by myself) and remained credits of each domainU.
> This part code is added to the csched_vcpu_acct() or csched_runq_sort(). I
> also try accessing to sdom->weight, it also does not work. OK, I will try to
> set up a serial console firstly. Thanks very much.

What's probably happening is that you're breaking invariants, and
hitting a "BUG_ON" or "ASSERT" somewhere else in the code.  While
you're getting your serial card set up, you could look at those
statements and see if your changes might be triggering any of them.

 -George

>
> Regards,
> Cong
>
> 2011/7/14 George Dunlap <George.Dunlap@eu.citrix.com>
>>
>> On Wed, Jul 13, 2011 at 5:54 PM, David Xu <davidxu06@gmail.com> wrote:
>> > Hi,
>> >
>> > I am changing the credit1 scheduler. But I encountered a problem that
>> > the
>> > system will crash if I use some fileds  of struct csched_dom (e.t.
>> > sdom->weight, sdom->credit ) frequently in the csched_vcpu_acct() or
>> > csched_runq_sort(). It seems strange. Can anyone give me some suggestion
>> > or
>> > share your experience? Thanks.
>>
>> Did you get any output on the serial console?
>>
>> If you don't have a serial console set up, that's the first thing to
>> do.  It's immensely helpful when doing Xen debugging, especially
>> scheduler stuff.
>>
>> You can learn more about setting up a Xen serial console here:
>>
>> http://wiki.xensource.com/xenwiki/XenSerialConsole
>>
>>  -George
>
>
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>
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