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  • To: "Mark Williamson" <mark.williamson@xxxxxxxxxxxx>
  • From: "Ashish Gupta" <ashishgup@xxxxxxxxx>
  • Date: Tue, 24 Apr 2007 13:08:20 -0500
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 24 Apr 2007 11:07:00 -0700
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Thanks Mark !  Actually the goal here is to remain black box....I am working on generic online techniques for a project, not really for a specific application.

Can't I also add tracing in the code that actually does the packet IO and disk IO in xen ? I need to figure out stats for both incoming and outgoing traffic. I have never really modified or played with the xen code so kind of warming up to what's really needed instead of getting lost in the code.

As for native Linux tools, if I run them in dom0 , will that be able to tell me all about disk and  network IO for the guest ? I am not allowed to run any thing inside domU to meet the black box requirement.


On 4/24/07, Mark Williamson <mark.williamson@xxxxxxxxxxxx> wrote:
> I am using xentrace to understand performance bottlenecks for an
> application inside domU.
> My question is how can I distinguish between network IO events and disk IO
> events using xentrace ?

I don't know if there are trace events currently generated for grant copy
operations - if not, you could add them and use these to judge the amount of
incoming network traffic.

Outgoing network traffic and disk IO are harder to distinguish since they both
just use temporary sharing grants.  It might be easier to use some sort of IO
monitoring tools within dom0 and the domU in question, similarly to as you
would on a native Linux system.

> A second related question is can I figure out disk queue waiting times and
> serving times (and similarly for the network) to figure out any bottlenecks
> or any external stress on these resources that may be causing the guest
> machine to be slowing down ?

Again, it's worth taking a look at native Linux tools.  XenMon may provide
some feedback but I imagine you might have already tried this?

For more complete profiling, Xenoprof allows you to run oprofile against
multiple domains (and Xen itself) at once).

> I greatly appreciate any advise/insight from fellow members here.

Sorry not to be more specific.


> cheers,
> Ashish
> On 23/1/07 19:31, "Rob Gardner" <rob.gardner@xxxxxx> wrote:
> >*> *
> >*> Grant transfers are no longer used to move network data from netback
> > to* *> netfront (except for backward compatibility with old netfront
> > drivers).* * *
> >* *
> >* Yeah, got that. ;)  Could you explain what mechanisms are currently
> > used* * to move data for net I/O and disk I/O between domains, and in*
> >* particular, can you suggest where in the code I could put trace calls
> > to* * be able to count I/O's? Thanks.*
> Everything is done via grant-map/unmap commands as it always was, except
> network receive (netback->netfront) which is done via grant-copy commands
> (one per contiguous fragment of network packet).
>  -- Keir

Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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