[Planetlab-users] concerning the behavior of planetlab2.cs.virginia.edu in the last two weeks

[Jawwad Shamsi]

Livia-
Have you tried using Sirius scheduler sevice?
I think it can help you in getting some clue.
For instance if during a "slow" time you assign a high priority to your
slice and notice an improvement during that 1-hour slot then definitley
the slow performance is due to the heavy load on that node.

Jawwad




> Hello all,
>
> I have been running some experiments using a distributed application
> (implemented by myself) in the planet-lab with 5 nodes, including
> planetlab2.cs.virginia.edu. In the last two weeks the performance of my
> application slowed down. As such performance depends on the workload of
> the node planetlab2.cs.virginia.edu I suppose this node slowed down due to
> some reason. I would like to have more information about such workload
> variability because this is very important to my performance studies.
> Particularly, If you have also been using this node in your experiments
> you can contribute with my studies.
>
> The objective of my experiments is to analyze the performance of a
> distributed
> application using the execution time as performance metric.
> In one of the experiments I used
> messages of 32KB. The execution time of the application was around 1
> second.
> However, from july 29th to august 13th, such execution times increased to
> 180 seconds. Presently, august 16th, the execution times are again around
> 1 second. The variability in the performance of the application is
> associated with the workload of the node  planetlab2.cs.virginia.edu. It
> seems that the node was "fast" and became "slow" for some
> period. This is not surprising in the planet-lab as pointed out in the
> paper "Fixing the embarrassing slowness of OpenDHT on Planetlab". However,
> I would like to have more information about the slowness of this specific
> node.
>
> In order to put some light on this topic I started investigating two
> possibilities: variabilities in the network load (to/from the
> node) or in the processing load (in the node). In the first
> case, I collected some
> traceroute data, in the periods the node was "fast" and "slow", trying to
> find some
> communication bottleneck - in this case, I configured the traceroute to
> send messages of 1KB. The traceroute data described the transmission of a
> message from each of the 5 nodes considered in my experiments to the same
> destination. I didn't noticed anything strange in the logs. Consequently,
> I suppose the reason for the variability in the performance of my
> application was due to an intensive use of the resources (eg. CPU, memory)
> of planetlab2.cs.virginia.edu by a number of applications running on this
> node, during the observed period, concurrently with my own application.
> Particularly, memory bound application can cause more swapout of the files
> been used. Moreover, applications with high priority can use more cpu
> cycles than the others.
>
> Another possibility is the intensive use of bandwidth causing fairsharing
> of available bandwidth, in this case, each slice of the same node cannot
> use the bandwidth limit specified for it. I suppose this is more critical
> as the number of applications running in different slices but on the same
> node increases.
>
> I would appreciate a lot if you could help me on this topic in the
> following way:
>
> 1. Have anybody run applications on planetlab2.cs.virginia.edu during the
> period from july 29th to august 13th? Is your application memory bound or
> does it require high bandwidth?
> 2. Is it possible to get information about CPU usage or memory consumption
> of a planet-lab node during some period in the past in order to identity
> the behavior of the applications competing with my own for the resources
> in the node planetlab2.cs.virginia.edu?
>
> I am looking forward to hearing from you...
> Lívia
>
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