[mpich-discuss] CPU usage versus Nodes, Threads

[Lu, Huiwei]

The cause of low utilization of CPU use can be blocking communications, load imbalance or thread contentions in your application.

What MPI calls are you using? Are they blocking or nonblocking? Are the load balanced on each node?

What thread level are your using? MPI_THREAD_MULTIPLE or MPI_THREAD_FUNNELED?

—
Huiwei

> On Oct 22, 2014, at 5:02 PM, Qiguo Jing <qjing at trinityconsultants.com> wrote:
> 
> Hi All,
>  
> We have a parallel program running on a cluster.  We recently found a case, which decreases the CPU usage and increase the run-time when increases Nodes.   Below is the results table.
>  
> The particular run requires a lot of data communication between nodes.
>  
> Any thoughts about this phenomena?  Or is there any way we can improve the CPU usage when using higher number of nodes?
>  
> Average CPU Usage (%)
> Number of Nodes
> Number of Threads/Node
> 100
> 1
> 8
> 92
> 2
> 8
> 50
> 3
> 8
> 40
> 4
> 8
> 35
> 5
> 8
> 30
> 6
> 8
> 25
> 7
> 8
> 20
> 8
> 8
> 20
> 8
> 4
>  
>  
> Thanks!
> 
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