Mailing List Archive: Question regarding xentrace

Question regarding xentrace

May 17, 2010, 11:58 PM

Post #1 of 4 (240 views)

Hi,

I've made some SAP benchmarks on my Xen system and discovered a huge
difference in the performance of a "xened" SAP system compared to a native
SAP system. Hence, I tried to figure out what might cause this 'overhead'
and run a xentrace (listining to all events). Xentrace produced 24gb data
and I converted it to 27gb human-readable data by using xentrace_format.
After I gathered the human-readable data, I filtered the data and counted
the appearance of each event. So far, so good.

Now it comes: although I used paravirt-guests, the xentrace-tool reported
HVM events in the trace data. Moreover, from my point of view it is
impossible to trace HVM events, as I use AMD Opteron 280 with no AMD-V
feature.

Did I miss something or does the xentrace-tool report 'wrong' trace data?

I use Xen version 3.2.0_16718_14-0.4 (from Suse).

Thanks
André

Re: Question regarding xentrace [ In reply to ]

dulloor at gmail

Jun 3, 2010, 1:02 PM

Post #2 of 4 (230 views)

Permalink

Are you using xentrace_format, xentrace, and xen all from the same
version ? I don't think the trace-ids are incompatible across
versions, but still.
Also, what HVM events are you seeing ?

-dulloor

On Mon, May 17, 2010 at 11:58 PM, André Bögelsack
<Andre.Boegelsack@in.tum.de> wrote:
> Hi,
>
> I've made some SAP benchmarks on my Xen system and discovered a huge
> difference in the performance of a "xened" SAP system compared to a native
> SAP system. Hence, I tried to figure out what might cause this 'overhead'
> and run a xentrace (listining to all events). Xentrace produced 24gb data
> and I converted it to 27gb human-readable data by using xentrace_format.
> After I gathered the human-readable data, I filtered the data and counted
> the appearance of each event. So far, so good.
>
> Now it comes: although I used paravirt-guests, the xentrace-tool reported
> HVM events in the trace data. Moreover, from my point of view it is
> impossible to trace HVM events, as I use AMD Opteron 280 with no AMD-V
> feature.
>
> Did I miss something or does the xentrace-tool report 'wrong' trace data?
>
> I use Xen version 3.2.0_16718_14-0.4 (from Suse).
>
> Thanks
> André
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>
>

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Re: Re: Question regarding xentrace [ In reply to ]

Andre.Boegelsack at in

Jun 7, 2010, 6:50 AM

Post #3 of 4 (243 views)

Permalink

I didn't change anything so I assume it is the same version across the
tools.

These are the events I gathered from xentrace:

It is not possible to call a HVM event on that hardware platform - the CPU
is too old.

My guess is, that the trace_id's recorded by xentrace and interpreted by
xentrace_format are not identical. Is there any way to prove it?

Regards
André

Dulloor <dulloor@gmail.com> schrieb am 03.06.2010 22:02:02:

> Von: Dulloor <dulloor@gmail.com>
> An: André Bögelsack <Andre.Boegelsack@in.tum.de>
> Kopie: xen-devel@lists.xensource.com
> Datum: 03.06.2010 22:02
> Betreff: Re: [Xen-devel] Question regarding xentrace
>
> Are you using xentrace_format, xentrace, and xen all from the same
> version ? I don't think the trace-ids are incompatible across
> versions, but still.
> Also, what HVM events are you seeing ?
>
> -dulloor
>
> On Mon, May 17, 2010 at 11:58 PM, André Bögelsack
> <Andre.Boegelsack@in.tum.de> wrote:
> > Hi,
> >
> > I've made some SAP benchmarks on my Xen system and discovered a huge
> > difference in the performance of a "xened" SAP system compared to a
native
> > SAP system. Hence, I tried to figure out what might cause this
'overhead'
> > and run a xentrace (listining to all events). Xentrace produced 24gb
data
> > and I converted it to 27gb human-readable data by using
xentrace_format.
> > After I gathered the human-readable data, I filtered the data and
counted
> > the appearance of each event. So far, so good.
> >
> > Now it comes: although I used paravirt-guests, the xentrace-tool
reported
> > HVM events in the trace data. Moreover, from my point of view it is
> > impossible to trace HVM events, as I use AMD Opteron 280 with no AMD-V
> > feature.
> >
> > Did I miss something or does the xentrace-tool report 'wrong' trace
data?
> >
> > I use Xen version 3.2.0_16718_14-0.4 (from Suse).
> >
> > Thanks
> > André
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@lists.xensource.com
> > http://lists.xensource.com/xen-devel
> >
> >

Re: Re: Question regarding xentrace [ In reply to ]

George.Dunlap at eu

Jun 7, 2010, 7:29 AM

Post #4 of 4 (235 views)

Permalink

Hmm, that would be rather exceptional... the trace_id's haven't really
changed since tracing was introduced, only new ones added. Are you sure
you're using the xentrace_format that matches up to the 3.2 hypervisor
you're using (and not, say, something from -unstable)? The format changed
from fixed-length records to variable-length records somewhere around there
(can't remember exactly).

If you take a really short trace (i.e., just let it run for 5 seconds before
interrupting), I can try to take a quick look at it, to see what I see.

-George

On Mon, Jun 7, 2010 at 2:50 PM, André Bögelsack
<Andre.Boegelsack@in.tum.de>wrote:

> I didn't change anything so I assume it is the same version across the
> tools.
>
> These are the events I gathered from xentrace:
>
>
> It is not possible to call a HVM event on that hardware platform - the CPU
> is too old.
>
> My guess is, that the trace_id's recorded by xentrace and interpreted by
> xentrace_format are not identical. Is there any way to prove it?
>
> Regards
> André
>
> Dulloor <dulloor@gmail.com> schrieb am 03.06.2010 22:02:02:
>
> > Von: Dulloor <dulloor@gmail.com>
> > An: André Bögelsack <Andre.Boegelsack@in.tum.de>
> > Kopie: xen-devel@lists.xensource.com
> > Datum: 03.06.2010 22:02
> > Betreff: Re: [Xen-devel] Question regarding xentrace
> >
> > Are you using xentrace_format, xentrace, and xen all from the same
> > version ? I don't think the trace-ids are incompatible across
> > versions, but still.
> > Also, what HVM events are you seeing ?
> >
> > -dulloor
> >
> > On Mon, May 17, 2010 at 11:58 PM, André Bögelsack
> > <Andre.Boegelsack@in.tum.de> wrote:
> > > Hi,
> > >
> > > I've made some SAP benchmarks on my Xen system and discovered a huge
> > > difference in the performance of a "xened" SAP system compared to a
> native
> > > SAP system. Hence, I tried to figure out what might cause this
> 'overhead'
> > > and run a xentrace (listining to all events). Xentrace produced 24gb
> data
> > > and I converted it to 27gb human-readable data by using
> xentrace_format.
> > > After I gathered the human-readable data, I filtered the data and
> counted
> > > the appearance of each event. So far, so good.
> > >
> > > Now it comes: although I used paravirt-guests, the xentrace-tool
> reported
> > > HVM events in the trace data. Moreover, from my point of view it is
> > > impossible to trace HVM events, as I use AMD Opteron 280 with no AMD-V
> > > feature.
> > >
> > > Did I miss something or does the xentrace-tool report 'wrong' trace
> data?
> > >
> > > I use Xen version 3.2.0_16718_14-0.4 (from Suse).
> > >
> > > Thanks
> > > André
> > > _______________________________________________
> > > Xen-devel mailing list
> > > Xen-devel@lists.xensource.com
> > > http://lists.xensource.com/xen-devel
> > >
> > >
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>
>